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West Nile virus (WNV) is a mosquitoborne virus that can cause severe and even fatal disease in humans. After WNV introduction into New York, NY, USA, its geographic range expanded [...]

ABSTRACT. During migration, Common and King Eiders (Somateria mollissima and S. spectabilis) cross the Beaufort and Chukchi Seas of Arctic Alaska. Because they may become attracted to lights, eiders are [...]

Research of and surveillance for influenza A viruses in wild birds inhabiting western Alaska have consistently provided support for the exchange of viruses between East Asia and North America via [...]

ABSTRACT. In 1972 we initiated a long-term study of Peregrine Falcons Falco peregrinas in West Greenland to evaluate population status and describe general breeding ecology. The study area encompassed approximately [...]

Neotropical migratory bird survivorship during the time they spend in wintering areas has been of major concern during the last several decades, yet still little is known about it. Evidence of behaviors that could increase the probability of individual survival, as well as increasing future reproductive success such as winter site fidelity and winter residency have gradually been documented for several migratory species. No evidence of these behaviors has been documented in urban areas. We present the results of a 9-year monitoring study in the green area of the Ethnobotanical Garden in the urban area of Oaxaca, Oaxaca, Mexico, using banding. Six of the 48 neotropical migratory species captured were selected for analysis of winter site fidelity and winter residency. The Warbling Vireo (Vireo gilvus) had the highest recapture rate (31.7%) with the highest winter fidelity (14.6%) and winter residency (24.4%). The next four species had recapture rates between 10.6-15.7%, winter fidelity between 6.0-10.4%, and winter residency between 5.1-19.1%. The Cedar Waxwing (Bombycilla cedrorum) demonstrated neither winter fidelity nor winter residency. Our results suggest urban green space areas may have an underestimated role in migratory bird conservation. Key words: banding, recapture, return, winter ground., Wintering biology of migratory birds has received substantial attention in the last several decades because the biotic and abiotic conditions that influence the non-reproductive stage have proved to have important [...]

Nearctic-neotropical passerines may spend up to one-third of the year in migration. Stopover sites have a critical role in providing migrant passerines with areas to rest and replenish fat stores. We characterized the stopover ecology of the Tennessee Warbler (Oreothlypis peregrina) at an inland site in Vicksburg, Michigan, using data from 4,607 warblers captured between 1990 and 2007. The recapture rate ranged from 1.6 to 12.1% annually and recaptured migrants averaged small but significant mass gains. Estimates of mass change using regression of mass on time of capture also suggested mass increases at this site. Recapture rate and mass gain estimated by regression varied significantly across the 18 years of study, although stopover length and mass change among recaptured individuals did not. Adult (after hatching year, AHY) warblers in active flight feather molt had an average lower mass and were four times more likely to be recaptured than non-molting adults. Over 95% of birds captured were hatching year (HY). The average condition and mass gains estimated by regression of HY warblers were lower than that of AHYs, but recapture rate, stopover length, and mass gains by recaptured individuals did not differ between the two age groups. The high number of captures and mass gains demonstrate the value of this site for fall migrant Tennessee Warblers. The annual differences in recapture rate and mass gains reported in this study suggest that several years of data may be needed to develop an accurate assessment of the typical use of a stopover site by migrants. Key words: age-related migration, annual variation, fall migration, inland stopover, mass change, molt, Oreothlypis peregrina., Nearctic-neotropical migrants spend up to a third of each year migrating, using stopover sites to rest and/or replenish their fat stores along the way (Mehlman et al. 2005). Migrants are [...]

About 200 North American Eared Grebes (Podiceps nigricollis californicus) at Tule Lake Refuge in northern California were observed engaging in successive waves of mass pattering and pattering flights on 25 May 2011. Most grebes present in a part of a canal were involved in this activity. Counts of grebes on the morning of 26 May suggest an important portion of the Eared Grebes seen in pattering could have left the area over night. The behavior was characterized as zugunruhe. Directed mass pattering of Eared Grebes may contribute to synchronization of the onward migration of the birds involved., North American Eared Grebes (Podiceps nigricollis californicus) are seldom seen in flight, except when they migrate (Bent 1919, Gaunt et al. 1990). The migration of the species has been well [...]

Post-breeding ecology of shrubland passerines prior to onset of migration is unknown relative to dynamics of breeding areas. We radiomarked and monitored 38 Sage Sparrows (Amphispiza belli ssp. nevadensis) at one site in Oregon and two in Nevada from September to mid-November 2007 to track local movements, estimate seasonal range sizes, and characterize weather patterns triggering onset of migration. Median area used by Sage Sparrows monitored between 3 and 18 days during or prior to migration was 14 ha; maximum daily movement was 15 km. Radio-marked Sage Sparrows at each location departed individually, rather than en masse, corresponding with passage of cold front weather systems. Conventional telemetry techniques limited our ability to monitor Sage Sparrows beyond pre-migratory periods and precluded detecting and tracking actual movements during migration. Received 13 December 2010. Accepted 20 May 2011., Sage Sparrows (Amphispiza belli ssp. nevadensis) are a species of conservation concern across their range, primarily due to loss of sagebrush (Artemisia spp.) habitats on which they depend (Knick and [...]

The distribution of landbirds during migration in forested landscapes of eastern North America is poorly known. We describe (1) the distribution of landbirds in northern white cedar (Thuja occidentalis) dominated forests as a function of distance from northern Lake Huron in Michigan during spring and autumn migration, and (2) discuss factors that may affect the distribution of these migrants. Both long- and short-distance migrants in spring and fall were concentrated within 0.4 km of the Lake Huron shoreline. This pattern was particularly pronounced during spring when aquatic-hatched insects such as midges and their predators (e.g., spiders) are most common and occur in largest numbers near the shoreline. Both long- and short-distance migrant abundance was associated with midge abundance, after controlling for date, during spring migration but not during fall migration. Migrants may concentrate near the shoreline because of the harrier effect of Lake Huron and relatively abundant food resources, especially during spring migration. Terrestrial habitats adjacent to bodies of water, where aquatic-dependent invertebrates are relatively abundant may provide important stopover sites for landbird migrants. Our results suggest coastal areas within the Great Lakes region provide critical stopover habitat for landbird migrants and should be a focus of conservation efforts, especially given the increasing development pressure that threatens these areas. Received 8 August 2009. Accepted 10 February 2011., Migration is a high-risk, energetically costly event (Alerstam and Lindstrom 1990, Blem 1990) that is associated with relatively high mortality (Moore et al. 1995, Sillett and Holmes 2002), especially among [...]

We conducted mist-net surveys of migrating songbirds during fall migration 2007 2009 on the 1,300-ha Albany Pine Bush Preserve (APBP), a fire-managed inland pitch pine-scrub oak (Pinus rigida-Quercus spp.) barren in east-central New York. We banded 244 migrating passerines from 32 non-resident species in 8,610 net/m/hr documenting use of northeastern pine barrens as stopover sites for passerines with diverse breeding ecologies. We estimated the breeding site origin of six species (a kinglet, four warblers, and a sparrow) using stable hydrogen isotope measurements from flight feathers. There was a broad range of isotope ratios within each species indicating a large catchment area extending several hundred kilometers north and west of the stopover site. Over half the birds originated >750 km from the APBP. We found no evidence for geographical structure of the timing of migration through APBP; slopes of regression lines for capture date versus hydrogen isotope ratio from feathers (δ[D.sub.f]) were not statistically different from zero. This contrasts with previous isotope research that reports both leapfrog and chain migration patterns by different warbler species at stopover sites in the western United States. Received 29 October 2010. Accepted 4 March 2011., Pine (Pinus spp.) barrens are globally rare, pyrogenic, early-successional ecosystems that support unique assemblages of species including many rare and declining taxa (Finton 1998, Barnes 2003, Latham 2003, Wagner et [...]

We document a female Burrowing Owl (Athene cunicularia) that nested in Arizona and dispersed 1,860 km to Saskatchewan, where she successfully raised seven young during the same breeding season. The dispersal path between these two locations has not been documented previously. This is the longest distance ever recorded for breeding dispersal for any raptor within the same breeding season and possibly for any bird species. Received 24 May 2010. Accepted 21 January 2011., Dispersal has important implications for population biology and evolution (Greenwood 1980, Wiens 2001). Breeding dispersal has been defined as movement between two successive breeding areas or social groups (Clobert et [...]

Evidence for climate-driven phenological changes is rapidly increasing at all trophic levels. Our current poor knowledge of the detailed control of bird migration from the level of genes and hormonal control to direct physiological and behavioral responses hampers our ability to understand and predict consequences of climatic change for migratory birds. In order to better understand migration phenology and adaptation in environmental changes, we here assess the scale at which weather affects timing of spring migration in passerine birds. We use three commonly used proxies of spring-time climatic conditions: (1) vegetation 'greenness' (NDVI) in Europe, (2) local spring temperatures in northern Europe, and (3) the North Atlantic Oscillation Index (NAO) as predictors of the phenology of avian migration as well as the strength of their effect on different subsets of populations and the dependence of correlations on species-specific migratory strategy. We analyze phenological patterns of the entire spring migration period in 12 Palaearctic passerine species, drawing on long-term data collected at three locations along a longitudinal gradient situated close to their northern European breeding area. Local temperature was the best single predictor of phenology with the highest explanatory power achieved in combination with NAO. Furthermore, early individuals are more affected by climatic variation compared to individuals on later passage, indicating that climatic change affects subsets of migratory populations differentially. Species wintering closer to the breeding areas were affected more than were those travelling longer distances and this pattern was strongest for the earliest subsets of the population. Overall, our results suggest that at least early subsets of the population are affected by local conditions and early birds use local conditions to fine-tune the date of their spring arrival while individuals arriving later are driven by other factors than local conditions e.g. endogenous control. Understanding what cues migratory organisms use to arrive at an optimum time is important for increasing our knowledge of fundamental issues like decision making in organisms during migration and is crucial for future protection of migratory organisms. doi: 10.1093/icb/icq028

For many years, orientation in migratory birds has primarily been studied in the laboratory. Although a laboratory-based setting enables greater control over environmental cues, the laboratory-based findings must be confirmed in the wild in free-flying birds to be able to fully understand how birds orient during migration. Despite the difficulties associated with following free-flying birds over long distances, a number of possibilities currently exist for tracking the long distance, sometimes even globe-spanning, journeys undertaken by migrating birds. Birds fitted with radio transmitters can either be located from the ground or from aircraft (conventional tracking), or from space. Alternatively, positional information obtained by onboard equipment (e.g., GPS units) can be transmitted to receivers in space. Use of these tracking methods has provided a wealth of information on migratory behaviors that are otherwise very difficult to study. Here, we focus on the progress in understanding certain components of the migration-orientation system. Comparably exciting results can be expected in the future from tracking free-flying migrants in the wild. Use of orientation cues has been studied in migrating raptors (satellite telemetry) and thrushes (conventional telemetry), highlighting that findings in the natural setting may not always be as expected on the basis of cage-experiments. Furthermore, field tracking methods combined with experimental approaches have finally allowed for an extension of the paradigmatic displacement experiments performed by Perdeck in 1958 on the short-distance, social migrant, the starling, to long-distance migrating storks and long-distance, non-socially migrating passerines. Results from these studies provide fundamental insights into the nature of the migratory orientation system that enables experienced birds to navigate and guide inexperienced, young birds to their species-specific winter grounds. doi: 10.1093/icb/icq065

We quantified resident and migrant bird attendance at army ant swarm raids (n = 48) in a neotropical montane forest. All observations were during seasons when Nearctic migrant birds are present. Bird species differed in army ant raid-attending behavior. Resident bird species attended 2 to 54% of raids, while migrants attended at lower maximum frequencies (2 to 21% of raids attended per species). Some resident and migrant bird species attended raids more frequently than expected based on capture rates in mist-net studies and point-count density surveys. Army ant raid attendance may be a regular element of foraging behavior for some resident species, and important in the wintering ecology of some Nearctic migrant species. The bird species that attended raids most frequently were predicted to show behavioral specializations for exploiting army ant swarms. Eight resident bird species (but no migrants) performed a specialized behavior, bivouac checking, by which birds sample army ant activity. Resident bird species' frequencies of raid attendance were positively associated with frequency of checking bivouacs (r = 0.68). We hypothesize the absence of obligate army ant-following birds in montane forests has favored performance of specialized behaviors for exploiting army ant raids by some resident birds. Received 3 October 2009. Accepted 9 March 2010., Neotropical army ants (Formicidae: Ecitoninae) are top predators, and a diverse array of animal species associate with army ant colonies (Franks 1982, Franks and Bossert 1983, Brady 2003, Koh et [...]

Eared Grebes (Podiceps nigricollis) in autumn make a postbreeding/molt migration from breeding areas in western North America to hypersaline lakes in the Great Basin. We studied their biology in 2001-2006 during this phase of the annual migration near Green River, Wyoming, USA where migrants en route to Great Salt Lake, Utah land on industrial ponds. Most evidently originate in the Prairie Pothole Region of North Dakota. The main movement extends from late July to mid-October. Migrants arrive almost daily with the cumulative percentage of transiting birds increasing by about 1% per day. Adult males and females migrate on the same schedule and precede juveniles by 2-3 weeks. Annual differences in phenology, abundance, age ratio, and wing molt vary with availability of wetland habitats in the main source area. Data on mass, body composition, energetics, and stomach contents indicate a typical flight involves a direct 2-3 day non-feeding migration, which is accomplished at night. Grebes are quiescent during the day and do not resume their migration until 45 min after sunset. We documented two undescribed vocalizations, a short-range contact note and one associated with departure. The possibility that Eared Grebe productivity, as inferred from studies of migrants through Wyoming, can provide insight into the status of waterbirds in the source area is worth further investigation., The autumnal migration of the Eared Grebe (Podiceps nigricollis) in North America occurs in two phases. Promptly after the breeding season adults and young undertake a postbreeding migration from nesting [...]

Global warming is impacting biodiversity by altering the distribution, abundance, and phenology of a wide range of animal and plant species. One of the best documented responses to recent climate change is alterations in the migratory behavior of birds, but the mechanisms underlying these phenotypic adjustments are largely unknown. This knowledge is still crucial to predict whether populations of migratory birds will adapt to a rapid increase in temperature. We monitored migratory behavior in a population of blackcaps (Sylvia atricapilla) to test for evolutionary responses to recent climate change. Using a common garden experiment in time and captive breeding we demonstrated a genetic reduction in migratory activity and evolutionary change in phenotypic plasticity of migration onset. An artificial selection experiment further revealed that residency will rapidly evolve in completely migratory bird populations if selection for shorter migration distance persists. Our findings suggest that current alterations of the environment are favoring birds wintering closer to the breeding grounds and that populations of migratory birds have strongly responded to these changes in selection. The reduction of migratory activity is probably an important evolutionary process in the adaptation of migratory birds to climate change, because it reduces migration costs and facilitates the rapid adjustment to the shifts in the timing of food availability during reproduction. doi/ 10.1073/pnas.0910361107 adaptation | bird migration | climate change | genetic variation | natural selection

Our understanding of migratory birds' year-round ecology and evolution remains patchy despite recent fundamental advances. Periodic reviews focus future research and inform conservation and management; here, we take advantage of our combined experiences working on Western Hemisphere avian migration systems to highlight recent lessons and critical gaps in knowledge. Among topics discussed are: (1) The pipeline from pure to applied researchers leaves room for improvement. (2) Population limitation and regulation includes both seasonal and between-season interactions, (3) The study of movements of small-bodied species remains a major research frontier. (4) We must increase our understanding of population connectivity. (5) With few exceptions, population regulation has barely been investigated. (6) We have increasingly integrated landscape configuration of habitats, large-scale habitat disturbances, and habitat quality impacts into models of seasonal and overall demographic success. (7) The post-breeding season (late summer for latitudinal migrants) is increasingly appreciated for its impacts on demography. (8) We recognize the diverse ways that avian brood parasites, nest predators, and food availability affect demography. (9) Source--sink and meta-population models help us understand migratory avian distributions among fragmented habitats. (10) Advances in modeling have improved estimates of annual survival and fecundity, but for few species. (11) Populations can be limited by ecological conditions in winter, but habitat needs are poorly known for most species at this time. (12) Migration tends to occupy broad spatial fronts that may change seasonally or when migrants cross major barriers. (13) En route conditions can limit migrant populations; linking migration habitat quality indicators to fitness or population consequences presents a major challenge. (14) A variety of intra-tropical Neotropical migration patterns are recognizable, but almost nothing is known about these systems beyond descriptions, of a few typical species' movements. (15) Global climate change scenarios predict range and phenology shifts of Neotropical migrant bird populations that must be considered in conservation plans. Future studies will depend on new technologies and the integration of modeling with sophisticated, large-spatial-scale measurement and parameter estimation; whether the pace of research and management involving migratory birds can match the growth of environmental threats remains to be seen. Key words: austral migration; breeding season population limitation; carry-over effects; connectivity; en route ecology; intratropical migration; land birds; migration; source-sink demography; winter population limitation.

Arthur T. Wayne collected 58 Yellow Rails (Coturnicops noveboracensis) during seven winters between 1903 and 1918 at one locality on the Atlantic coast in Charleston County, South Carolina. The collection represents the largest known series of Yellow Rails from a single wintering site and provides information about the winter ecology of this species. There was no evidence that Yellow Rail numbers varied between winters. The sex ratio was significantly biased toward females suggesting the occurrence of differential wintering. Yellow Rails were collected mainly in wet (freshwater) fields with short dense grass, the same features of Yellow Rail habitats in coastal Texas. Yellow Rails were consistently located in the same habitats as LeConte's Sparrow (Ammodramus leconteii). Two other grassland species, Henslow's Sparrows (A. henslowii) and Sedge Wrens (Cistothorus palustris), had habitat occupancy patterns significantly different from that of Yellow Rails., The Yellow Rail (Coturnicops noveboracensis) has been studied in breeding areas (Peabody 1922, Terrill 1943, Stalheim 1974, Anderson 1977, Bookhout and Stenzel 1987, Gibbs et al. 1991, Robert and Laporte [...]

I investigated the relative importance of floristics and physiognomy in determining community organization of autumn-migrating landbirds in a riparian corridor in New Mexico invaded by Tamarisk (Tamarix ramosissima). All six avian measures were associated with floristics, physiognomy, or both. However, usefulness in predicting migrant parameters differed between floristics and physiognomy, and depended on the vegetation measures used (direct measures vs. plant community-structure indices) and the scale investigated (micro- vs. macrohabitat). Using direct vegetation measures, migrant abundance, energy consumption, and evenness were more strongly associated with floristics than with physiognomy at all scales. Contrastingly, migrant species richness and diversity were more strongly associated with physiognomy than with floristics at the microhabitat scale, and appeared to be unrelated to vegetation measures at the macrohabitat scale. Migrant species composition was similar among floristically similar macrohabitats, but it was equally correlated with floristics and physiognomy at the microhabitat scale. Using plant community- structure indices, migrant species composition and evenness remained strongly associated with the floristic measure (plant species diversity). However, floristic diversity was most important in predicting migrant abundance and diversity, whereas both floristic and physiognomic (horizontal structure) diversity were important in predicting migrant energy consumption. Migrant species richness was not associated with plant community structure. Respective relationships of floristics and physiognomy to food resources and foraging substrates might explain observed bird-vegetation associations. The results indicated that floristics and physiognomy are both useful in predicting avian community organization in exotic vegetation, and such information can guide conservation and management strategies that seek to control Tamarix while protecting migrant landbirds and their stopover habitats. Key words: community organization, exotic, floristics, migrants, physiognomy, riparian, Tamarix. Investigue la importancia relativa de las caracteristicas floristicas y de la fisonomia en determinar la organizacion comunitaria de las aves terrestres migratorias de otono en un corredor ribereno invadido por Tamarix ramosissima en Nuevo Mexico. Las seis medidas recolectadas de las aves estuvieron asociadas con las caracteristicas floristicas, la fisonomia, o ambas. Sin embargo, la utilidad en predecir los parametros migratorios difirio entre las variables floristicas y las fisonomicas, y dependio de los tipos de medidas de vegetacion utilizadas (medidas directas vs. indices de estructura de la comunidad) y de la escala investigada (micro- vs. macro-habitats). Utilice medidas directas de la vegetacion y comprobe que la abundancia de aves migratorias, el consumo de energia y la equidad estuvieron mas fuertemente asociadas con la floristica que con la fisonomia a todas las escalas. En contraste, la riqueza y la diversidad de las especies migratorias estuvieron mas fuertemente asociadas con la fisonomia que con la floristica a escala de micro-habitat, y parecieron no estar relacionadas con las medidas de la vegetacion a la escala de macro-habitat. La composicion de especies migratorias fue similar entre macro-habitats con caracteristicas floristicas similares, pero estuvo igualmente correlacionada con las condiciones floristicas y la fisonomia a la escala de micro-habitat. Utilizando los indices de estructura de la comunidad vegetal, la composicion y la equidad de las especies migratorias permanecieron fuertemente asociadas con la medida floristica (diversidad de especies de plantas). Sin embargo, la diversidad floristica fue mas importante en predecir la abundancia y la diversidad de aves migratorias, mientras que la diversidad floristica y fisonomica (estructura horizontal) fueron importantes en predecir el consumo de energia de las aves migratorias. La riqueza de especies migratorias no estuvo asociada con la estructura de la comunidad vegetal. Las relaciones respectivas de las caracteristicas floristicas y fisonomicas con los recursos alimenticios y con los sustratos de forrajeo podrian explicar las asociaciones observadas entre las aves y la vegetacion. Los resultados indicaron que las caracteristicas floristicas y la fisonomia son ambas utiles en predecir la organizacion de la comunidad de aves en la vegetacion exotica. Esta informacion puede guiar las estrategias de conservacion y manejo que buscan controlar a Tamarix y al mismo tiempo proteger a las aves migratorias terrestres y los habitats donde estas hacen sus escalas migratorias.

Understanding the patterns, extent, and phenology of migration is important for estimating potential influences of habitat or climate changes on populations of migratory birds. We used satellite telemetry of >100 individual King Eiders (Somateria spectabilis) tagged in northwestern North America in 2002-2006 to describe the timing and extent of their migration and winter movements in the Bering Sea. We found high variability in timing of migration events and distances flown. Arrival on breeding grounds and onset of molt migration were the least variable events in duration. Fall migration was extremely variable, ranging from less than a week to several months. More than a third of King Eiders did not migrate after wing molt and wintered on or near wing-molting areas. We found diffuse migratory connectivity between breeding and wintering areas, and low intrayear fidelity to 25 km radius wintering sites. More than half of the King Eiders used several wintering sites in a given year, and their winter ranges were considerably larger than those of other sea duck species. We identified three distinct wintering regions in the Bering Sea that were several hundred km apart, among which no movements occurred from late December until April. The onset of spring migration was earlier for birds wintering farther south, but arrival time on breeding grounds was not correlated with wintering latitude. We conclude that high phenotypic plasticity in migratory traits may render King Eiders more likely to respond to environmental shifts than sea duck species that show stronger migratory connectivity. Key words: King Eider, migration, migratory connectivity, satellite telemetry, Somateria spectabilis. Para estimar la influencia potencial de cambios climaticos, o de habitat, en las poblaciones de aves migratorias, es importante comprender los patrones, la extension y la fenologia de su migracion. Nuestro estudio utilizo telemetria satelital de >100 individuos de Somateria spectabilis, marcados con transmisores en el noroeste de America del Norte (2002-2006), para describir la extension de la migracion y los movimientos invernales de estas aves en el Mar de Bering. Encontramos un alto nivel de variacion respecto a la sincronia y a las distancias de vuelo de los movimientos migratorios. El arribo a las zonas de apareamiento y el inicio de la muda de migracion fueron los eventos menos variables. La migracion otonal fue altamente variable, con una variacion desde menos de una semana, hasta varios meses. Mas de un tercio de los individuos de S. spectabilis no migraron despues de la muda en las alas, pasando el invierno en, o cerca de, la zona de muda. Encontramos una conectividad migratoria difusa entre las areas de apareamiento y las de invernada, y baja fidelidad a sitios de invernada de 25 km de radio en un mismo invierno. Mas de la mitad de los individuos de S. spectabilis utilizaron varios sitios de invernada durante cada ano, y las areas de invernada fueron considerablemente mas amplias que las de otras especies de patos marinos. Identificamos tres regiones distintas de invernada en el Mar de Bering separadas por varios cientos de kilometros. Entre estas, no ocurrieron movimientos desde fines de diciembre hasta abril. El inicio de la migracion de primavera fue mas temprano para las aves que invernaron mas al sur, pero el tiempo de arribo a las areas de apareamiento no resulto estar correlacionado con la latitud de la invernada. Concluimos que, en S. spectabilis, una alta plasticidad fenotipica en los rasgos migratorios puede hacer mas probable que estas aves respondan a cambios ambientales, en comparacion a aquellas especies de patos marinos que muestran una mayor conectividad migratoria.

We investigate the effects of body mass and breeding habitat use on the timing and location of the fall molt of western Neotropical migrant passerines. Most western migrants that molt within their breeding ranges breed in coniferous forests, while most that move south before molting breed in low elevation broadleaf or open habitats. We show that larger passerines take longer to molt than smaller passerines and that larger species are more likely to migrate south before molting, whereas smaller species are more likely to molt in their breeding ranges, presumably because their molts take less time. To test our habitat results, we surveyed Cassin's Vireos (Vireo cassinii) during their breeding and molting season in Washington to assess up-slope movements. Vireos that bred in low elevation coniferous forest (usually ponderosa pine [Pinus ponderosa] or Douglas-fir [Pseudotsuga menziesii]) moved up-slope at least 300 m to molt in wetter, high-elevation Douglas-fir forests. Key words: molt and elevation, molt-migration, molt rate, size and up-slope movement, Vireo cassinii. Investigamos el efecto de la masa corporal y del habitat de anidacion sobre el momento y lugar en que sucede la muda en aves paserinas neotropicales. La gran mayoria de las especies de paserinos migratorios occidentales que mudan dentro de su ambito de anidacion lo hacen en bosques de coniferas, mientras que muchas de las especies que migran hacia al sur antes de mudar, anidan a elevaciones menores en habitats abiertos o en bosques caducifolios. Encontramos que en los paserinos mas grandes el tiempo de muda es mayor en comparacion con las especies de menor tamano. Ademas, las especies de mayor tamano tienden a migrar hacia al sur antes de la muda, mientras que los paserinos pequenos tienden a mudar en el mismo sitio de anidacion, probablemente debido a que el tiempo de muda es mas corto. Para poner a prueba nuestros resultados acerca del habitat de anidacion, realizamos censos de Vireo casiini durante la temporada de anidacion y de muda en el estado de Washington para evaluar los movimientos altitudinales. Los individuos que anidaron a elevaciones bajas en los bosques de confieras se desplazaron por lo menos 300 m cuesta arriba a finales del verano, para mudar en bosques de coniferas mas humedos de alta elevacion.

We contrast patterns of variation in morphological traits of migratory and sedentary forms of the Yellow-rumped Warbler (Dendroica coronata) to test functional predictions regarding the evolution of traits related to flight. Sedentary individuals are larger than migrants in all traits except bill width and depth. However, when traits are adjusted for body size differences using multivariate approaches, migrants have longer and more concave wings than do individuals from sedentary populations, suggesting selection for high--aspect ratio wings for fast, sustained flight. Subadults have relatively shorter and rounder wings than do adults of all subspecies except for the long-distance migrant D. c. coronata, and age-related differences are most pronounced in short-distance migrants. We propose a graphic model for the evolution of age-related differences in wing shape that is based on the role of antagonistic selective pressures imposed by migratory flight vs. maneuverability. Size-adjusted differences in tail length are not significant. Longer culmens and tarsi in the sedentary D. c. goldmani subspecies of Guatemala suggest differences in diet and foraging behavior compared to migratory groups. Our results strongly suggest that divergent natural selection has caused the morphological differentiation between migratory and sedentary subspecies. Key words: Dendroica, ecomorphology, flight, ontogenetic shift, warbler, wing shape. Contrastamos los patrones de variacion en caracteres morfologicos de poblaciones migratorias y sedentarias de Dendroica coronata para probar predicciones funcionales referentes a la evolucion de caracteres relacionados con el vuelo. Los individuos sedentarios son mas grandes que los migratorios en todos los caracteres, a excepcion del ancho y alto del pico. Sin embargo, cuando los caracteres son corregidos por tamano corporal utilizando metodos multivariados, las poblaciones migratorias tienen alas mas largas y concavas que las sedentarias, lo cual sugiere el papel de la seleccion natural en producir alas puntiagudas para el vuelo rapido sostenido. Los subadultos tienen alas mas cortas y mas redondeadas que los adultos en todos los grupos excepto en la subespecie migratoria de larga distancia D. c. coronata, y las diferencias entre edades son mas pronunciadas en las migratorias de corta distancia. Proponemos un modelo grafico para la evolucion de las diferencias en la forma del ala segun la edad, que se basa en el papel de fuerzas selectivas antagonicas impuestas por el vuelo migratorio y la maniobrabilidad. Las diferencias en el tamano de la cola ajustadas por tamano corporal no son significativas. La mayor longitud del pico y el tarso de la subespecie sedentaria D. c. goldmani de Guatemala sugiere la existencia de diferencias en la dieta y la conducta de forrajeo con respecto alas migratorias. Nuestros resultados sugieren que la seleccion natural es la principal causa de la diferenciacion morfologica entre poblaciones migratorias y sedentarias.

Sindbis virus (SINV), a mosquito-borne virus that causes rash and arthritis, has been causing outbreaks in humans every seventh year in northern Europe. To gain a better understanding of SINV [...]

Migratory birds have been implicated in the long-range spread of highly pathogenic avian influenza (HPAI) A virus (H5N1) from Asia to Europe and Africa. Although sampling of healthy wild birds [...]

Seasonal fruits are an important food resource for small songbirds during autumn migration in southern New England. Therefore, conservation and management of important stopover sites used by migrating birds requires knowledge about nutritional requirements of songbirds and nutritional composition of commonly consumed fruits. We measured nutrient composition and energy density of nine common fruits on Block Island, Rhode Island, and conducted a field experiment to estimate consumption rates of three of these fruits by birds during autumn migration. Most common fruits on Block Island contained primarily carbohydrates (41.3-91.2% dry weight), and little protein (2.6-8.6%) and fat (0.9-3.7%), although three contained more fat: Myrica pennsylvanica (50.3%), Viburnum dentatum (41.3%), and Parthenocissus quinquefolia (23.6%). Bird consumption of high-fat, high-energy V. dentatum fruit and high-carbohydrate, low-energy Phytolacca americana fruit was greater than consumption of Aronia melanocarpa, a high-carbohydrate, low-energy fruit. We estimated that migratory birds on Block Island must eat up to four times their body mass in fruit wet weight each day to satisfy their energy requirements when eating low-energy fruits such as P. americana, and they cannot satisfy their protein requirements when eating only certain high-energy fruits such as V. dentatum. Our results suggest that many migratory birds must eat both fruits and insects to meet their dietary needs. Thus, shrubland habitat at important migratory stopover sites such as Block Island should be managed so that it contains a variety of preferred fruit-bearing shrubs and an adequate abundance of insects., Many species of migratory songbirds that are primarily insectivorous during the breeding season consume large amounts of fruit during autumn migration (Thompson and Willson 1979, Herrera 1984, Parrish 1997), even [...]

We delineate the winter distributions of the five subspecies of Saltmarsh Sharp-tailed (Ammodramus caudacutus) and Nelson's Sharp-tailed (A. nelsoni) sparrows, and comment on patterns of migration. The two subspecies of A. caudacutus (A. c. caudacutus, A. c. diversus) have similar core winter ranges that extend along the Atlantic coast from North Carolina to northeastern Florida. They also occupy two isolated areas within peninsular Florida in Everglades National Park and on the northwest Gulf coast. Migration in A. caudacutus is mainly confined to the coast. The subspecies of A. nelsoni (A. n. nelsoni, A. n. alterus, A. n. subvirgatus) occupy different but overlapping winter ranges. A. n. nelsoni is the most widespread, occurring from North Carolina to Texas. Some birds migrate along the Atlantic coast southwards in fall, and others follow interior routes through the Mississippi River watershed in both fall and spring. We suggest A. n. nelsoni wintering along the Atlantic coast in spring fly directly inland towards their northern breeding areas. Some birds in fall also approach the southeastern coastline directly across the Appalachian Mountains. A. n. alterus mainly winters along the southeastern Atlantic coast to Florida, and in fewer numbers along the Gulf coast at least to Louisiana. Some A. n. alterus may migrate to the Gulf coast directly via inland routes west of the Appalachian Mountains. A. n. subvirgatus has the most limited wintering distribution, from South Carolina to northeast Florida, and is strictly a coastal migrant south of New England. Limited wintering ranges and narrow winter habitat requirements place continental populations of sharp-tailed sparrows at risk., Breeding populations of sharp-tailed sparrows are distributed in three discrete regions of mostly once-glaciated North America. For nearly 65 years these sparrows were treated as a single species (AOU 1931). [...]

Historically, studies of habitat selection have focused on quantifying how current patterns of habitat occupancy influence condition and survival within a season. This approach, however, is overly simplistic, especially for migratory birds that spend different periods of the year in geographically distinct places. Habitat occupancy and the resulting condition of individual birds is likely to be affected by events in the previous season, and the consequences of habitat occupancy will influence individuals and populations in subsequent seasons. Thus, for migratory birds, variation in habitat quality (and quantity) needs to be understood in the context of how events interact throughout periods of the annual cycle. Seasonal interactions can occur at the individual level or population level. Individual-level interactions occur when events in one season produce nonlethal, residual effects that carry over to influence individuals the following season. Population-level interactions occur when a change in population size in one season influences per capita rates the following season. We review various methods for estimating seasonal interactions and highlight a number of examples in the literature. Using a variety of techniques, including intrinsic and extrinsic markers, the vast majority of studies to date have measured seasonal interactions at the individual level. Obtaining estimates of density and changes in per capita rates across multiple seasons to determine population-level interactions has been more challenging. Both types of seasonal interactions can influence population dynamics, but predicting their effects requires detailed knowledge of how populations are geographically connected (i.e., migratory connectivity). We recommend that researchers studying habitat occupancy and habitat selection consider how events in previous seasons influence events within a season. Key words: carry-over effects, habitat selection, interseasonal density effects, migration, migratory connectivity, population size. Historicamente los estudios sobre seleccion de habitat se han enfocado en cuantificar como los patrones de ocupacion de habitat en un momento determinado influencian la condicion y supervivencia de las aves dentro de una estacion. Sin embargo, este enfoque es demasiado simplista, especialmente para las aves migratorias que pasan diferentes periodos del ano en lugares geograficos diferentes. La ocupacion de un habitat y la consecuente condicion de cada individuo son influenciadas muy probablemente por los eventos ocurridos en las epocas anteriores, y las consecuencias de la ocupacion de un habitat determinado influenciaran tanto a los individuos como a las poblaciones en las epocas futuras. De este modo, deben entenderse las variaciones en la calidad (y cantidad) de habitat para las aves migratorias en el contexto de la interaccion de los diferentes eventos ocurridos a traves del ciclo anual. Las interacciones estacionales pueden ocurrir tanto a nivel de individuo como de poblaciones. Las interacciones a nivel de individuo ocurren cuando un evento en una estacion produce un efecto residual y no letal que influencia a los individuos durante la epoca siguiente. Las interacciones a nivel poblacional ocurren cuando un cambio en el tamano poblacional en una epoca influencia las tasas per capita en la epoca siguiente. En este estudio, revisamos varios metodos para estimar las interacciones estacionales y resaltamos una variedad de ejemplos de la literatura. Hasta ahora la mayoria de los estudios han medido interacciones estacionales solo a nivel de individuo, utilizando variadas tecnicas que incluyen marcadores intrinsecos y extrinsecos. La obtencion de datos sobre cambios en la densidad y en las tasas per capita a traves de multiples epocas para determinar interacciones a nivel poblacional ha sido mucho mas dificil. Ambos tipos de interacciones pueden influenciar las dinamicas poblacionales, pero la prediccion de sus efectos requiere de un conocimiento detallado de la conexion geografica de las poblaciones (i.e., conectividad migratoria). Recomendamos que los investigadores que estudian patrones de ocupacion y de seleccion de habitat tomen en consideracion el modo en que los eventos en una epoca determinada son influenciados por los eventos que ocurrieron en las epocas anteriores.

In migrant birds, winter social systems reflect strategies of habitat use. The best-studied strategy is that of a fixed home range of territory. Alternative strategies to holding a territory, such as floating and flocking behaviors, suggest different processes of habitat selection. Whereas flocking, like territoriality, is a well-studied social strategy, solitary nonterritorial (floater) behavior is difficult to study and is thus poorly understood in terms of its causes, consequences, and implications for habitat selection. Floaters are individuals of a primarily stationary population which move over large areas compared to the average home range size. We review evidence of the causes, consequences, and frequency of winter floating behavior, focusing primarily on migrant songbirds. We also address the endocrine basis of alternative behavioral strategies by presenting results from aviary-based dominance trials with Hermit Thrushes (Catharus guttatus). Results from this study and others suggest that the adrenocortical response to social stress plays a key role in both the proximate and ultimate causes of floating behavior. Because winter floating behavior exists in many migrant songbird species, better understanding of winter floaters may be important for population modeling and conservation planning. Key words: alternative behaviors, corticosterone, floaters, habitat selection, social systems, territoriality, winter. En las aves migratorias, los sistemas sociales de invierno reflejan las estrategias de uso de habitat. La estrategia mejor estudiada es la de un territorio o un rango de hogar fijo. Las estrategias alternativas para mantener un territorio, como los comportamientos de bandada y de individuos flotantes, sugieren procesos de seleccion de habitat diferentes. Mientras que el comportamiento de bandada, al igual que la territorialidad, es una estrategia social bien estudiada, el comportamiento no territorial (flotante) es dificil de estudiar. Por esto, el comportamiento flotante es muy poco entendido en terminos de sus causas, consecuencias e implicancias para la seleccion de habitat. Los individuos flotantes pertenecen a poblaciones mayoritariamente fijas que se mueven a traves de grandes areas en comparacion con el rango de hogar promedio. Revisamos la evidencia sobre las causas, las consecuencias y las frecuencias del comportamiento flotante en invierno, enfocandonos principalmente en las aves migratorias. Tambien abordamos la base endocrina de las diferentes estrategias de conducta presentando resultados de experimentos de dominancia en aviarios, utilizando a Catharus guttatus. Los resultados de este y otros estudios sugieren que la respuesta adenocortical al estres social juega un papel clave tanto en las causas inmediatas como en las causas ultimas del comportamiento flotante. Debido a que el comportamiento flotante durante el invierno existe en varias especies migratorias de aves canoras, un mejor entendimiento sobre los flotantes durante la epoca invernal podria ser muy importante para construir modelos poblacionales y establecer planes de conservacion.

Stopover habitat quality may influence the abundance of migrant landbirds, yet little is known about how spatial and temporal changes in stopover habitat quality influence the use of habitats by migrant landbirds. From late April to late May, 1997-1999, we surveyed migrant landbirds within five habitats (early successional shrub-sapling-stage forest, midsuccessional pole-stage forest, mature forest interior, mature forest--agricultural edge, and mature suburban forest) in central Pennsylvania. To assess relative quality of stopover habitats, we measured species abundance, species richness, and foraging behavior of Yellow-rumped Warblers (Dendroica coronata). We measured vegetation structure and phenology to examine proximate cues of potential importance in habitat selection. Of nine transient (nonbreeding) species analyzed, seven--Least Flycatcher (Empidonax minimus), Nashville Warbler (Vermivora ruficapilla), Northern Parula (Parula americana), Magnolia Warbler (D. magnolia), Black-throated Blue Warbler (D. caerulescens), Yellow-rumped Warbler, and Blackpoll Warbler (D. striata)--were most abundant in mature forests, and especially edge-dominated mature forests (forest-agricultural edge and suburban forest). Habitats used by mature-forest-breeding transients changed between years, but edge-dominated forest types were used most frequently in all three years. Although canopy leaf development at mature forest sites showed little relationship to site use by mature-forest-breeding transients within weekly intervals, year-to-year differences in leaf phenology were consistent with year-to-year changes in habitat use by migrant landbirds. Foraging behavior of Yellow-rumped Warblers suggested higher food availability and quality in forest-agricultural edges, compared with suburban forest and forest interior. Mature-forest-breeding transients were positively associated with sites that had large trees (>38 cm diameter at breast height) and denser understory vegetation (stems 0-2.5 cm in diameter). Extensive use of mature edge-dominated forests by migrating forest birds during spring suggests that these habitats may be important for the conservation of migrant landbirds. Received 25 October 2004, accepted 22 September 2006. Key words: migration, Nearctic-Neotropical migrant landbirds, Pennsylvania, stopover habitat. La calidad del habitat de los sitios de escala migratoria puede influenciar la abundancia de las aves migratorias terrestres, pero se conoce poco acerca de como los cambios espaciales y temporales en la calidad del habitat de estos sitios influencian el uso de los habitats por estas aves. Entre finales de abril y finales de mayo de 1997 a 1999, realizamos censos de aves terrestres migratorias en cinco ambientes (matorrales sucesionales tempranos-bosques en estadio de renovales, bosques en estadios de sucesion media, interior de bosques maduros, bordes entre bosques maduros y areas agricolas y bosques maduros suburbanos) en el centro de Pensilvania. Para evaluar la calidad relativa de los habitats de escala migratoria, medimos la abundancia de especies, la riqueza de especies y el comportamiento de forrajeo de Dendroica coronata. Medimos la estructura de la vegetacion y la fenologia para examinar las variables proximas potencialmente empleadas por las aves para seleccionar los habitats. De nueve especies transeuntes (no reproductivas) analizadas, siete--Empidonax minimus, Vermivora ruficapilla, Parula americana, Dendroica magnolia, D. coronata, D. caerulescens y D. striata--fueron mas abundantes en los bosques maduros, y especialmente en los ambientes dominados por bordes (borde entre bosque y areas agricolas y bosque suburbano). Los ambientes utilizados por las especies transeuntes que se reproducen en bosques maduros cambiaron entre anos, pero los tipos de bosque dominados por bordes fueron los mas frecuentemente utilizados en los tres anos. Aunque a intervalos semanales el desarrollo de las hojas del dosel en los sitios de bosque maduro mostro poca relacion con el uso de los sitios por parte de las especies transeuntes que se reproducen en bosques maduros, las diferencias entre anos en la fenologia de las hojas fueron concordantes con los cambios anuales en el uso de habitat por parte de las aves migratorias terrestres. El comportamiento de forrajeo de D. coronata sugirio que la abundancia y la calidad del alimento son mayores en los bordes entre bosques y areas agricolas que en los bosques suburbanos y el interior de bosque. Las especies transeuntes que se reproducen en bosques maduros se asociaron positivamente con los sitios que presentaban arboles grandes (>38 cm de diametro a la altura del pecho) y vegetacion mas densa en el sotobosque (tallos de 0-2.5 de diametro). El uso considerable de bosques maduros dominados por bordes por parte de aves migratorias de bosque durante la primavera, sugiere que esos ambientes podrian ser importantes para la conservacion de las aves migratorias terrestres.

Counts of visible migrants at traditional watchsites throughout North America provide an opportunity to augment population-monitoring efforts for birds of prey. We analyzed hourly counts of migrating raptors at one inland (Hawk Mountain Sanctuary, Pennsylvania) and one coastal (Cape May Point, New Jersey) watchsite in northeastern North America. Hourly counts of migrants have been collected for 38 years at Hawk Mountain Sanctuary and for 28 years at Cape May Point. We compared effort-adjusted, arithmetic-mean passage rates to five geometric-mean indexes for 12 species. We used reparameterized polynomial regression to estimate trends in the indexes and to test the significance of trends from 1976-1978 (average index over three-year period) to 2001-2003. Effort-adjusted, arithmetic-mean indexes corresponded to more sophisticated indexes on the complete data sets but did not perform well on simulated data with missing observation days. We recommend the use of a regression-based, date-adjusted index for the analysis of hawk-count data. This index produced trends similar to other geometric-mean indexes, performed well on data sets simulating reduced sampling frequency, and outperformed other indexes on data sets with large blocks of missing observation days. Correspondence between trends at the watchsites and trends from Breeding Bird Surveys (BBSs) suggests that migration counts provide robust estimates of population trends for raptors. Furthermore, migration counts allow the monitoring of species not detected by BBS and produce trends with greater precision for species sampled by both methods. Analysis of migration counts with appropriate methods holds considerable promise for contributing to the development of integrated strategies to monitor raptor populations. Key words: Falconiformes, migration monitoring, population index, population trends, raptors. Los conteos realizados en sitios tradicionales de avistamiento en Norte America son un buen recurso para aumentar los esfuerzos de monitoreo de las poblaciones de aves rapaces. Analizamos datos de conteos de aves rapaces migratorias realizados cada hora en una isla (Hawk Mountain Sanctuary, Pensilvania) y en un sitio de observacion en la costa (Cape May Point, Nueva Jersey) ubicados en el noreste de Norte America. Estos conteos han sido colectados por 38 anos en Hawk Mountain Sanctuary y por 28 anos en Cape May Point. Comparamos las medias aritmeticas de las tasas de paso, ajustadas por esfuerzo, con cinco indices de medias geometricas para 12 especies. Utilizamos regresiones polinomiales reparametrizadas para estimar las tendencias de los indices y para probar si las tendencias entre 1976-1978 (indice promediado por un periodo de tres anos) y 2001-2003 son significativas. Los indices de media aritmetica ajustados por esfuerzo fueron indicies mas sofisticados para la base de datos completa, pero estos no se desempenaron bien con los datos simulados en que faltan algunos dias de observacion. Para el analisis de los datos de conteo de halcones recomendamos el uso de un indice basado en un analisis de regresion ajustado por fecha. Este indice produjo tendencias similares a las de otros indices de media geometrica, se desempeno bien con datos que simularon una frecuencia de muestreo reducida y se desempeno mejor que otros indices calculados con base en datos con grandes bloques de ausencias de dias de observacion. La correspondencia entre las tendencias en los sitios de observacion y las tendencias registradas con los conteos de aves reproductivas (Breeding Bird Surveys), sugiere que los conteos de aves migratorias representan una estimacion robusta de las tendencias poblacionales de las aves rapaces. Ademas, los conteos de aves migratorias permiten el monitoreo de especies que no son detectadas con los conteos de aves reproductivas y generan tendencias mas precisas para las especies que son detectadas por los dos metodos. El analisis de los conteos de aves migratorias mediante metodos adecuados constituye una buena oportunidad para contribuir al desarrollo de estrategias integradas para monitorear las poblaciones de aves rapaces.

Measurement of stable-hydrogen isotopes ([delta]D) in feathers of migrating birds can provide information on where feathers were grown in North America, at least to an approximate band of latitude. This approach has greatly increased our ability to investigate aspects of avian migration and stopover ecology, since origins of unmarked individuals at migration stopover sites can be estimated for the first time. However, few studies have explored the power of combining isotope measurements with geographic information system (GIS) methods. We measured [delta]D values in feathers of hatching-year (HY) Swainson's Thrushes (Catharus ustulatus; n = 60), Wood Thrushes (Hylociehla mustelina; n = 113), and Gray Catbirds (Dumetella carolinensis; n = 158) at Ft. Morgan Peninsula, Alabama (30[degrees]10'N, 88[degrees]00'W), a migration stopover site along the Gulf coast. By applying an elevation-corrected hydrogen isotope basemap for birds in North America, we derived a GIS surface depicting expected feather [delta]D values across the continent. We then used GIS to constrain the possible origins of the sampled populations by considering only values falling within the North American breeding ranges of the species. We depicted likely origins of migrating birds by the 50% and 75% tolerance limits of the data. Our GIS analysis indicated that our captured populations represented much-reduced regions of possible origin based on the North American breeding distributions. Gradients in abundance data from the North American Breeding Bird Survey (BBS) allowed us to further narrow possible origins within isotopic boundaries for Wood Thrushes and Gray Catbirds. This exercise provided a means by which priority regions and habitats could be assessed at large continental scales based on actual productivity. We suggest the combination of isotopic and GIS tools provides a powerful means to derive conservation priorities and to investigate key factors involved in the ecology of avian migration and stopover. Key words: deuterium, geographic information systems, migratory connectivity, stable isotopes, stopover. La medicion de isotopos estables de hidrogeno ([delta]D) en las plumas de las aves migratorias puede proveer informacion importante acerca del lugar geografico en Norteamerica donde crecieron las plumas, o por lo menos aproximar la localizacion dentro de una banda latitudinal especifica. Esta tecnica ha aumentado considerablemente nuestra capacidad de investigar aspectos de la migracion y la ecologia de las paradas migratorias de las aves, debido a que por primera vez es posible determinar el origen de individuos no marcados en sitios de paradas migratorias. Sin embargo, pocos estudios han explorado el poder de combinar medidas de isotopos con metodos de sistemas de informacion geografica (SIG). En este estudio, medimos los valores de [delta]D en plumas de individuos de las especies Catharus ustulatus (n = 60), Hylocichla mustelina (n = 113) y Dumetella carolinensis (n = 158) en su ano de eclosion en la peninsula de Ft. Morgan, Alabama (30[degrees]10'N, 88[degrees]00'W), un sitio de paradas migratorias en la costa del Golfo. Mediante la aplicacion de un mapa base de isotopos de hidrogeno corregido por la elevacion para las aves de Norteamerica y utilizando un SIG, derivamos una superficie que representa los valores de [delta]D esperados para plumas en todo el continente. Luego utilizamos el SIG para restringir los posibles origenes de la poblacion muestreada, considerando solo los valores que cayeran dentro de los rangos de distribucion reproductiva de las especies en Norteamerica. Representamos los posibles origenes de las aves migratorias mediante los limites de tolerancia de los datos del 50% y del 75%. Nuestro analisis de SIG indico que las poblaciones capturadas representaban distribuciones mucho mas reducidas con base en las distribuciones reproductivas de las aves de Norteamerica. Datos de gradientes de abundancia provenientes de la base de datos de conteos de aves reproductivas de Norteamerica nos permitieron aproximar aun mas los posibles origenes dentro de los limites sugeridos por los isotopos para H. mustelina y D. carolinensis. Este ejercicio represento un medio para determinar regiones y habitats prioritarios para la conservacion a una escala continental con base en la productividad real de las regiones. Sugerimos que el uso combinado de tecnicas de isotopos y SIG representa un medio poderoso para determinar prioridades para la conservacion, y para investigar factores clave sobre la ecologia de la migracion y las paradas migratorias.

We conducted large-scale, systematic sampling of influenza type A virus in migratory waterfowl (mostly mallards [Anas platyrhynchos]) at Ottenby Bird Observatory, southeast Sweden. As with previous studies, we found a [...]

Assigning conservation priorities to areas used by birds during migration requires information on the relative quality of areas and habitats. The rate at which migratory birds replenish energy reserves during stopover may be used as an indicator of stopover-site quality. We estimated the rate of mass gain of 34 landbird species during stopover at a near-shore terrestrial site on the south shore of Lake Ontario in New York during 12 migration seasons from 1999 to 2004. The average rate of mass gain was estimated by relating a measure of condition to time of capture (hour after sunrise) with linear regression. Data from 25,385 captures were analyzed. Significantly positive rates of mass change were detected for 20 of 30 species during spring migration and 19 of 21 species during autumn migration. No significantly negative trends were detected in either season. Daily rates of mass gain across all species averaged 9.84% of average lean body weight during spring migration and 9.77% during autumn migration. Our regression estimates were significantly greater than estimates from traditional analyses that examine mass changes in recaptured birds. Analyses of mass changes in recaptured birds revealed a mean daily change of -0.68% of average lean mass in spring and 0.13% in autumn. Because of sampling biases inherent in recapture analyses, the regression approach is likely more accurate when the assumptions of the method are met. Similar studies in various habitats, landscapes, and regions are required to prioritize conservation efforts targeting migratory stages of the annual cycle. Key words: bird migration, landbirds, mass gain, stopover. Asignar prioridades de conservacion a areas que son utilizadas por aves durante la migracion requiere de informacion sobre la calidad relativa de estas areas y habitats. La tasa a la cual las aves se reaprovisionan de reservas energeticas durante las paradas migratorias puede ser utilizada como un indicador de la calidad de los sitios de parada. Estimamos la tasa de incremento de peso de 34 especies de aves terrestres durante paradas migratorias en un sitio cercano a la costa en la ribera sur del Lago Ontario en Nueva York durante 12 estaciones migratorias desde 1999 hasta 2004. La tasa promedio de incremento de peso se estimo relacionando una medida de condicion al momento de captura (una hora despues del amanecer) mediante regresion lineal. Se analizaron datos de un total de 25,385 capturas. Se detectaron cambios significativos en el peso para 20 de 30 especies durante las migraciones de primavera y para 19 de 21 especies durante las migraciones de otono. No se detectaron tendencias negativas en ninguna de las dos estaciones. Las tasas diarias de incremento de peso para todas las especies representaron en promedio un incremento de un 9.84% del peso corporal magro promedio durante la migracion de primavera y de un 9.77% durante la migracion de otono. Nuestras estimaciones, basadas en analisis de regresion, fueron significativamente mayores que las estimaciones basadas en analisis tradicionales que examinan los cambios en el peso de aves recapturadas. Los analisis de cambio de peso en las aves recapturadas revelaron un cambio diario promedio de -0.68% del peso promedio magro en primavera y de 0.13% en otono. Debido al sesgo de muestreo inherente al analisis de recaptura, el metodo de regresion es mas exacto si se cumplen de manera adecuada los supuestos de este metodo. Se requieren estudios similares en diferentes habitats, paisajes y regiones para dar prioridad a los esfuerzos en conservacion que apunten a las distintas etapas migratorias durante el ciclo anual.

Recent work in Michigan's eastern Upper Peninsula suggests that terrestrial areas bordering northern Lake Huron provide important stopover habitat for spring migrating landbirds, principally because of the presence of emergent aquatic midges (Diptera: Chironomidae). Migrants were concentrated in lakeshore habitats abundant with midges during spring migration. American Redstarts (Setophaga ruticilla) and Black-throated Green Warblers (Dendroica virens) foraged and used habitat differently, depending on their distance from the lakeshore. Here, we describe results of an integrative study in which we sampled resources, quantified American Redstart foraging behavior, and estimated mass change in American Redstarts and five other common migrant landbird species to evaluate the importance of adult midges as an early season resource for spring migrants. Resource sampling and American Redstart foraging behavior suggested that more food was available in shoreline habitats than inland during spring migration. Furthermore, migrants gained mass in shoreline habitat during stopover, which supports the argument that nearshore areas provide important stopover habitat for spring migrants. Finally, resource sampling, mass change estimates, and American Redstart foraging behavior suggested that midges and spiders (Araneae: Arachnidae) provided an important early season resource for migrating landbirds. Evidence suggests that midges were responsible for elevated spider abundance at the shoreline and that birds foraged on both midges and spiders. Midges appear to play an important role in providing high-quality stopover habitat for landbirds migrating through Michigan's eastern Upper Peninsula. Key words: aquatic insects, landbird migrant, resources, stopover ecology. Trabajos recientes en el este de la parte superior de la Peninsula de Michigan sugieren que las areas terrestres a lo largo de la orilla del Lago Huron representan un habitat importante para las paradas de aves migratorias terrestres durante la primavera, principalmente debido a la presencia de insectos acuaticos emergentes (Diptera: Chironomidae). Las aves migratorias se concentraron en los habitats de ribera del lago, los cuales presentan una alta abundancia de quironomidos durante la migracion de primavera. Individuos de Setophaga ruticilla y Dendroica virens forrajearon y utilizaron de distintas maneras el habitat, dependiendo de sus distancias a la orilla del lago. Aqui, describimos resultados de un estudio que integra muestreos de recursos, cuantificacion del comportamiento de forrajeo de S. rutinilla y estimaciones de los cambios en el peso de S. rutinilla y otras cinco especies de aves migratorias terrestres comunes, para evaluar la importancia de los quironomidos adultos como un recurso disponible tempranamente en la estacion para las aves migratorias de primavera. El muestreo de recursos y el comportamiento de forrajeo de S. rutinilla sugirieron que la disponibilidad de alimento era mayor cerca de la orilla del lago que en los habitats interiores durante la migracion de primavera. Ademas, las aves migratorias ganaron peso corporal durante las paradas en los habitats riberenos, lo que apoya el argumento de que las areas riberenas son un habitat importante para las aves durante las paradas migratorias de primavera. Finalmente, el muestreo de recursos, las estimaciones del cambio en el peso y el comportamiento de S. rutinilla sugirieron que tanto los quironomidos como las aranas (Araneae: Arachnidae) proveyeron de un recurso importante durante la fase temprana de la estacion para las aves terrestres migratorias. La evidencia sugiere que los quironomidos fueron responsables de la elevada abundancia de aranas en las orillas del lago y que las aves forrajearon tanto quironomidos como aranas. Los quironomidos parecen tener un papel importante en proveer de habitat de alta calidad para las paradas migratorias de aves terrestres que migran a traves de la parte este y superior de la Peninsula de Michigan.

Open population models using capture-mark-recapture (CMR) data have a wide range of uses in ecological and evolutionary contexts, including modeling of stopover duration by migratory passerines. In using CMR approaches in novel contexts there is a need to determine the conditions under which open population models may be employed effectively. Our goal was to determine whether there was a simple a priori mechanism of determining the conditions under which CMR models could be used effectively in the study of avian stopover ecology. Using banding data (n = 188 capture histories), we examined the challenges of using CMR-based models due to parameter inestimability, adequacy of descriptive power (Goodness-of-Fit, GOF), and parameter uncertainty. These issues become more apparent in studies with limited observations in a capture history, as is often the case in studies of avian stopover duration. Limited sample size and sampling intensity require an approach to reducing the number of fitted parameters in the model. Parameter estimability posed the greatest restriction on the utility of open population models, with high parameter uncertainty posing a lesser challenge. Results from our study also indicate the need for > 10 observations per estimated parameter (approximately 3 birds captured or recaptured per day) to provide a reasonable chance of successfully estimating all model parameters. Received 13 July 2005, accepted 20 May 2006., Migratory birds frequently use stopovers to complete migration successfully between their breeding and wintering grounds. Stopover sites provide refuge from predators, protection against inclement weather, and food resources to allow [...]

We compared migrating behavior of Broad-winged Hawks (Buteo platypterus) at two sites along their migration corridor: Hawk Mountain Sanctuary in eastern Pennsylvania and the Kekoldi Indigenous Reserve in Limon, Costa Rica. We counted the number of times focal birds intermittently flapped their wings and recorded the general flight type (straight-line soaring and gliding on flexed wings versus circle-soaring on fully extended wings). We used a logistic model to evaluate which conditions were good for soaring by calculating the probability of occurrence or absence of wing flaps. Considering that even intermittent flapping is energetically more expensive than pure soaring and gliding flight, we restricted a second analysis to birds that flapped during observations, and used the number of flaps to evaluate factors influencing the cost of migration. Both the occurrence and extent of flapping were greater in Pennsylvania than in Costa Rica, and during periods of straight-line soaring and gliding flight compared with circle-soaring. At both sites, flapping was more likely during rainy weather and early and late in the day compared with the middle of the day. Birds in Costa Rica flew in larger flocks than those in Pennsylvania, and birds flying in large flocks flapped less than those flying alone or in smaller flocks. In Pennsylvania, but not in Costa Rica, the number of flaps was higher when skies were overcast than when skies were clear or partly cloudy. In Costa Rica, but not in Pennsylvania, flapping decreased as temperature increased. Our results indicate that birds migrating in large flocks do so more efficiently than those flying alone and in smaller flocks, and that overall, soaring conditions are better in Costa Rica than in Pennsylvania. We discuss how differences in instantaneous migration costs at the two sites may shift the species' migration strategy from one of time minimization in Pennsylvania to one of energy minimization in Costa Rica. Received 15 November 2005, accepted 8 July 2006., Each year, more than one million Broad-winged Hawks (Buteo platypterus) make a round-trip migration of 6,000-10,000 km along the Mesoamerican Land Corridor when traveling between their North American breeding grounds [...]

The Semipalmated Plover (Charadrius semipalmatus), an arctic-nesting migratory shorebird, regularly encounters low temperatures during the breeding season. We measured the basal metabolism of adults during incubation at Churchill, Manitoba, Canada to determine basal metabolic rate (BMR), lower critical temperature ([T.sub.1c]), total evaporative water loss (TEWL), and dry thermal conductance ([C.sub.m]). BMR and [T.sub.1c] were 47.4 kJ [day.sup.-1] and 23.3[degrees]C, respectively, TEWL was 2.5 mL [H.sub.2][O.sup.-d], and [C.sub.m] was 1.13mW [g.sup.-1] [degrees][C.sup.-1]. Measured BMR and [T.sub.1c] were consistent with high values found for other shorebird species breeding in the Arctic, while [C.sub.m] was 18% higher than predicted from allometric equations. These metabolic data suggest that Semipalmated Plovers are adapted to balance the requirements of incubation against energetic and thermoregulatory demands in the Arctic, especially in harsh early breeding season conditions. Key words: Arctic, basal metabolic rate, Charadrius semipalmatus, lower critical temperature, Semipalmated Plover, thermal conductance, total evaporative water loss. Charadrius semipalmatus es un ave playera migratoria que anida en el artico y esta regularmente expuesta a bajas temperaturas durante le epoca reproductiva. Medimos el metabolismo basal de individuos adultos en Churchill, Manitoba, Canada, para determinar el indice de metabolismo basal (IMB), la temperatura critica baja (T[.sub.1c]), 1a perdida total de agua pot evaporacion (PTAE) y la conduccion termica seca ([C.sub.m]). El IMB fue 47.4 kJ [dia.sup.1], 1a [T.sub.1c] fue 23.3[degrees]C, la PTAE fue 2.5mL [H.sub.2][O.sup.-d] y la [C.sub.m] fue 1.13mW [g.sup.-1] [degrees][C.sup.-1]. Los valores medidos de IMB y [T.sub.1c] fueron consistentes con los altos valores registrados para otras especies de aves playeras que se reproducen en el artico, mientras que la [C.sub.m] fue 18% mas alta que la predicha por ecuaciones alometricas. Esta informacion metabolica sugiere que C. semipalmatus esta adaptado a balancear los requerimientos de incubacion en funcion de las demandas energeticas y de termo-regulacion en el artico, especialmente durante condiciones adversas al inicio de la epoca reproductiva.

We combined Breeding Bird Survey point count protocol and distance sampling to survey spring migrant and breeding birds in Vicksburg National Military Park on 33 days between March and June of 2003 and 2004. For 26 of 106 detected species, we used program DISTANCE to estimate detection probabilities and densities from 660 3-min point counts in which detections were recorded within four distance annuli. For most species, estimates of detection probability, and thereby density estimates, were improved through incorporation of the proportion of forest cover at point count locations as a covariate. Our results suggest Breeding Bird Surveys would benefit from the use of distance sampling and a quantitative characterization of habitat at point count locations. During spring migration, we estimated that the most common migrant species accounted for a population of 5000-9000 birds in Vicksburg National Military Park (636 ha). Species with average populations of >300 individuals during migration were: Blue-gray Gnatcatcher (Polioptila caerulea), Cedar Waxwing (Bombycilla cedrorum), White-eyed Vireo (Vireo griseus), Indigo Bunting (Passerina cyanea), and Ruby-crowned Kinglet (Regulus calendula). Of 56 species that bred in Vicksburg National Military Park, we estimated that the most common 18 species accounted for >8150 individuals. The six most abundant breeding species, Blue-gray Gnatcatcher, White-eyed Vireo, Summer Tanager (Piranga rubra), Northern Cardinal (Cardinalis cardinalis), Carolina Wren (Thryothorus ludovicianus), and Brown-headed Cowbird (Molothrus ater), accounted for >5800 individuals. Key words: breeding bird survey, density, detection probability, distance sampling, loess bluff forest, migration. Combinamos datos de censos de aves reproductivas realizados mediante un protocolo de conteos pot punto con muestreos en que se registra la distancia para censar las aves migratorias de primavera y las residentes en Vicksburg National Military Park durante 33 dias entre marzo y junio de 2003 y 2004. Para 26 de las 106 especies detectadas, empleamos el progama DISTANCE para estimar las probabilidades de deteccion y las densidades a partir de 660 conteos por punto de 3 minutos de duracion, en los que las detecciones fueron registradas en cuatro rangos de distancia alrededor de los puntos de conteo. Para la mayoria de las especies, los estimados de la probabilidad de deteccion (y por lo tanto de la densidad) se mejoraron mediante la incorporacion de la proporcion de cobertura boscosa en el sitio de conteo como una covariable. Nuestros resultados sugieren que los censos de aves reproductivas se beneficiarian del uso de muestreos con distancia y de caracterizaciones cuantitativas del habitat en los puntos de conteo. Durante la migracion de primavera, estimamos que las especies de migrantes mas comunes representaron una poblacion de 5000 a 9000 aves en Vicksburg National Military Park (636 ha). Las especies con tamanos poblacionales promedio mayores que 300 individuos durante la migracion fueron Polioptila caerulea, Bombycilla cedrorum, Vireo griseus, Passerina cyanea y Regulus calendula. Estimamos que mas de 8150 de los individuos correspondieron alas 18 especies mas comunes entre las 56 que se reprodujeron en el area de estudio. Mas de 5800 individuos pertenecieron alas seis especies reproductivas mas abundantes: P. cerulea, V. griseus, Piranga rubra, Cardinalis cardinalis, Thryothorus ludovicianus y Molothrus ater.

Speed (km/hr) during flight is one of several factors determining the rate of migration (km/ day) and flight range of birds. We attached 26-g, back-mounted satellite-received radio tags (platform transmitting terminals; PTTs) to adult female Northern Pintails (Anas acuta) during (1) midwinter 2000-2003 in the northern Central Valley of California, (2) fall and winter 2002-2003 in the Playa Lakes Region and Gulf Coast of Texas, and (3) early fall 2002-2003 in south-central New Mexico. We tracked tagged birds after release and, in several instances, obtained multiple locations during single migratory flights (flight paths). We used data from 17 PTT-tagged hens along 21 migratory flight paths to estimate groundspeeds during spring (n = 19 flights) and fall (n = 2 flights). Pintails migrated at an average groundspeed of 77 ± 4 (SE) km/hr (range for individual flight paths = 40-122 km/hr), which was within the range of estimates reported in the literature for migratory and local flights of waterfowl (42-116 km/hr); further, groundspeed averaged 53 ± 6 km/hr in headwinds and 82 ± 4 km/hr in tailwinds. At a typical, but hypothetical, flight altitude of 1,460 m (850 millibars standard pressure), 17 of the 21 flight paths occurred in tailwinds with an average airspeed of 55 ± 4 km/hr, and 4 occurred in headwinds with an average airspeed of 71 ± 4 km/hr. These adjustments in airspeed and groundspeed in response to wind suggest that pintails migrated at airspeeds that on average maximized range and conserved energy, and fell within the range of expectations based on aerodynamic and energetic theory. Received 19 November 2004, accepted 6 September 2005., The overall rate at which birds travel during migration, often referred to as migration speed (measured in km/day), includes the time required to accumulate fat reserves and rest prior to [...]

Accurate estimates of annual survival are necessary for conservation of threatened species of migratory birds. We studied a large, stable population of Kentish Plovers (Charadrius alexandrinus) breeding in southern Turkey (36[degrees]43'N, 35[degrees]03'E) for five breeding seasons (1996-2000). Kentish Ptovers of Eurasia and the conspecific Snowy Plover of North America are a species of conservation concern. We captured 2077 birds, and used time since marking models to estimate apparent survival ([??] and encounter rates (p) for juvenile and adult plovers. Return rates of young banded in their natal year were low (4%, 52 of 1176) and most philopatric young were recaptured as yearlings (69%, 36 of 52). Low return rates of shorebird young can be attributed to post-hatching mortality if apparent survival rates are ranked: chicks < fledglings = adults. We were unable to separate mortality from dispersal because apparent survival was ranked: chicks ([[??].sup.1] = 0.08) < fledglings ([[??].sup.1] = 0.15) < adults after banding ([[??].sup.1] = 0.59) < adults in later intervals ([[??].sup.2+] = 0.64). Time since marking models gave improved estimates of the apparent survival of adults that were higher than return rates in other populations of Kentish Plovers, but lower than estimates of apparent survival for other Charadrius plovers. Sex-biased mating opportunities in Kentish Plovers were not explained by biased sex ratios at hatching or differential apparent survival among adults. Instead, male-biased adult sex ratios were explained, in part, by differential survival of juveniles and by higher encounter rates among adult males (p = 0.84) than females (p = 0.74). Our baseline estimates of apparent survival will assist assessments of population viability for Kentish and Snowy Plovers throughout their geographic range. Key words: age at maturity, Charadrius alexandrinus, demography, mark-recapture, sex ratio, Snowy Plover.

Twice each year, millions of night-migratory songbirds migrate thousands of kilometers. To find their way, they must process and integrate spatiotemporal information from a variety of cues including the Earth's magnetic field and the night-time starry sky. By using sensory-driven gene expression, we discovered that night-migratory songbirds possess a tight cluster of brain regions highly active only during night vision. This cluster, here named 'cluster N,' is located at the dorsal surface of the brain and is adjacent to a known visual pathway. In contrast, neuronal activation of cluster N was not increased in nonmigratory birds during the night, and it disappeared in migrants when both eyes were covered. We suggest that in night-migratory songbirds cluster N is involved in enhanced night vision, and that it could be integrating vision-mediated magnetic and/or star compass information for nighttime navigation. Our findings thus represent an anatomical and functional demonstration of a specific night-vision brain area. behavioral molecular mapping | bird orientation | cognition | magnetic sense | ZENK (zif268, Egr-1, NGF-1A, and Krox-24)

We summarized published and unpublished information on the reproductive biology and ecology of Jabirus (Jabiru mycteria) in Belize. From 1968 to 1987, 91 individual nests were discovered in 16 of 19 breeding seasons; 69 nests were confirmed as active. Jabiru nests were 15-30 m above ground in Ceiba pentandra (five nests), Pinus caribaea (five nests), Tabebuia ochracea (one nest), Acoelorrhaphe wrightii (one nest), and dead trees (three nests). Most nests (32 of 36) were located in northern and central Belize in isolated, tall, emergent trees (trees with crowns that stand above the surrounding canopy). Nest trees were usually surrounded by riparian forests or seasonally inundated pine-savanna wetlands situated in transitional zones where pine savannah meets coastal lowlands. Two nests were used for at least 10 years. The breeding season began with the transition from wet to dry season (November-December). Earliest eggs were observed on 12 December 1973 and latest eggs on 26 February 1987. Earliest nestlings were observed on 15 January 1970, and young were seen on nests as late as 28 May 1973. Young birds fledged 100 to 115 days after hatching but were still dependent on parents. From 1968 to 1987, a total of 44 eggs and 92 nestlings were counted. Mean clutch size was 3.14 ± 1.17 SE (range = 1-5 eggs, n = 14 nests). Hatching success for four nests during the 1972-1973 breeding season was 43.8%. For 14 years in which crude hatching success (nestlings per active nest) could be calculated, 71.6% (43 of 60) of all active nests had at least one nestling. The mean number of nestlings per nest was 2.13 ± 0.71 SE (range = 1-4 nestlings, n = 43 nests). Productivity (the number of nestlings per nest for all active nests) was 1.53. These results were similar to those of two other studies of Jabiru breeding biology conducted in Brazil and Venezuela. Jabiru populations in Belize appear to have increased since the species gained protected status in 1973. Received 23 July 2004, accepted 4 March 2005., Jabirus (Jabiru mycteria) breed locally from southern Mexico (Campeche, Tabasco) through the lowlands of Central America and east of the Andes to northern Argentina (Bent 1926, Blake 1977, Knoder et [...]

Capture--mark--recapture models require estimation of parameters that may be either constant or time-dependent. Open-population models have been adapted for use in estimating stopover duration of migratory songbirds. However, with data collected over an extended period or with relatively few recaptures, small sample sizes may preclude use of fully time-dependent models. Pooling is commonly used to reduce the number of parameters estimated in time-dependent models. In pooling, all captures and recaptures during a specified interval are treated as a single capture event, which results in a loss of information about recaptures within the interval. Additionally, pooling of banding data of migratory songbirds appears to bias stopover-length estimates upwards. An alternative to pooling is use of multiple-day-constancy models. Advantages of this approach include maintenance of all recapture data, simultaneous Akaike's Information Criterion-based comparison of models using different constancy intervals, and unbiased stopover estimates. Received 15 June 2003, accepted 6 October 2004. Key words: capture-mark-recapture, migration, open population models, stopover duration. Los modelos de captura-marcado-recaptura requieren la estimacion de parametros que pueden ser ya sea constantes o dependientes del tiempo. Los modelos de poblaciones abiertas han sido adaptados para estimar la duracion de las paradas de aves canoras migrantes. Sin embargo, con datos colectados a lo largo de un periodo extenso o con relativamente pocas capturas, los tamanos de muestra pequenos pueden impedir el uso de modelos totalmente dependientes del tiempo. Usualmente se combinan estos datos para reducir el numero de parametros estimados en modelos dependientes del tiempo. Al combinar los datos, las capturas y recapturas obtenidas durante un intervalo de tiempo determinado son tratadas como un evento de captura unico, lo que conduce a una perdida de informacion de las recapturas dentro del intervalo determinado. Ademas, la combinacion de los datos de anillado de aves canoras migratorias parece sobrestimar la duracion de las paradas. Una alternativa a la combinacion de datos es usar modelos de constancia de multiples dias. Las ventajas de este enfoque incluyen el mantenimiento de todos los datos de recaptura, la comparacion de modelos basados en el Criterio de Informacion de Akaike usando intervalos de constancia diferentes y estimaciones no sesgadas de la duracion de los periodos de escala migratoria.

The measurement of the abundance of naturally occurring deuterium ([delta]D) in feathers grown in North America can provide geographical information on location where the feather was grown. Previously, we used this technique to link populations of Bicknell's Thrush (Catharus bicknelli) breeding in northeastern North America (to 46[degrees]N) with wintering grounds in the Dominican Republic. That study indicated the presence of a subpopulation of wintering birds with more depleted feather [delta]D values than those measured on their known breeding grounds. This suggested either a more northerly or a higher altitude breeding source population than previously measured. We located two populations of Bicknell's Thrush in Quebec, Canada, at Mine Madeleine (49[degrees]N) and at Mont Gosford (45[degrees]N). The Mine Madeleine birds had feather [delta]D values overlapping those of the unidentified subpopulation found wintering in the Dominican Republic. At Mont Gosford, hatch-year birds were more depleted in their feather [delta]D values than after-second-year birds suggesting their more northerly origins and capture during the early fall migration period. Our study demonstrates how the stable-isotope approach can be used to document connectivity between breeding and wintering populations of migratory birds. Key words: Catharus bicknellii, deuterium, migratory connectivity, stable isotopes.

Many, but not all, juvenile Spruce Grouse (Falcipennis canadensis) disperse from their natal range in autumn. In spring shortly before breeding, some of these autumn dispersers will disperse a second time from their winter range, whereas others make their first dispersal from natal range. I postulated that dispersing first in autumn provides greater experience on a potential breeding area than immigrating to the breeding area in spring. I predicted that autumn-immigrant females would show a higher percentage of females nesting, would nest earlier, and would produce more juveniles into late summer than would immigrants in spring. Data were available for females on three areas widely spaced across their geographic range. Immigrants contributed most to production. Parameters did not vary greatly among study areas. Combining all areas, 68% of autumn immigrants and 69% of spring immigrants were known to nest, mean hatch dates relative to the annual median differed by less than 1 day, and spring immigrants produced more juveniles surviving into late summer than did autumn immigrants (1.1 versus 0.7 juveniles per female). Hence, there is no evidence yet that autumn dispersal directly confers a reproductive advantage for female Spruce Grouse. Results underscore a perplexing question: if site-specific conditions stimulate winter residents to emigrate, why do the spring immigrants that replace them fare so well? Key words: dispersal, Falcipennis Canadensis, reproduction, Spruce Grouse, winter residency.

We collected prey remains from 25 Peregrine Falcon (Falco peregrinus) territories across Arizona from 1977 to 1988 yielding 58 eyrie-years of data. Along with 793 individual birds (107 species and six additional genera), we found seven mammals and nine insects. In addition, two nestling peregrines were consumed. We found a larger dependence upon White-throated Swifts (Aeronataes saxatalis) and birds on migration in northern Arizona, while in southeastern and central Arizona average prey mass was greater and columbiforms formed the largest dietary component. In northern, central, and southeastern Arizona, 74, 66, and 56 avian prey taxa, respectively, were recorded. We used capture-recapture modeling to estimate totals of 111 [+ or -] 9.5, 113 + 10.5, and 86 [+ or -] 7.9 (SE) avian taxa taken in these same three areas. These values are counterintuitive inasmuch as the southeast has the richest avifauna. For the entire study area, 156 [+ or -] 9.3 avian taxa were estimated to be taken by peregrines. Key words: Arizona, diet, Falco peregrinus, Peregrine Falcon, prey.

Previous interspecific studies have shown that migratory birds have a higher prevalence of blood parasites than nonmigratory birds. It is thought that birds that move greater distances are exposed to a larger parasite fauna, because of uneven distribution of vectors that carry such parasites. Current hypotheses also suggest that the stress of migration may allow parasites to persist, by weakening the immune system and allowing latent infections to recur. We captured migrating hatching-year Sharp-shinned Hawks (Accipiter striatus) in New Mexico and estimated natal latitudes of each individual by analyzing stable-hydrogen isotope ratios of feathers. That enabled us to estimate distances traveled up to point of capture. We also collected blood to quantify hematozoan infection prevalence and intensity. We related distance traveled to prevalence and intensity of hematozoan infections. Contrary to previous hypotheses, our results show no relationship between distance traveled by migrants and prevalence and intensity of hematozoan infections. Of 75 individuals examined, 24% were infected with Leucocytozoon toddi, 37% with Haemoproteus elani, and 5% with H. janovyi. To our knowledge, this is the first documented occurrence of H. janovyi in North America and in Sharp-shinned Hawks. Our stable-hydrogen isotope analyses indicated that H. janovyi was detected only in birds that originated in southwestern North America, which may be of significance in regard to biogeography of that parasite species.