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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

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.

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.

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.

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.

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 [...]

Using standardized mist-net captures collected over a 32-year period (1970-2001), we examined changes in the capture rates of passerines recorded in coastal Massachusetts during fall (78 species) and spring (72 species) migration. Capture rates of 45 species of fall migrants (58%) declined significantly between early (1970-1985) and late (1986-2001) years of the study; 36 species of spring migrants (50%) showed significant declines. Only Carolina Wren (Thryothorus ludovicianus), Tufted Titmouse (Baeolophus bicolor), Northern Cardinal (Cardinalis cardinalis), and Orchard Oriole (Icterus spurius) showed significant increases during spring migration; fall sampling indicated that Carolina Wren, Tufted Titmouse, Black-throated Blue Warbler (Dendroica caerulescens), and Northern Cardinal had significantly higher capture rates. Of 37 species included in the migration monitoring data but not reliably represented by Breeding Bird Survey (BBS) data in any of the northeastern physiographic strata, 23 (62%) showed significant declines at Manomet during at least one of the two migration periods. There were significant correlations in percent changes in migrant capture rates between fall and spring. BBS trends reported from the southern New England and northern New England physiographic strata were correlated with changes in migrant capture rates. However, there were also inconsistencies between results obtained by the two monitoring approaches, suggesting that factors in addition to actual changes in breeding populations may be reflected in the migration capture data. Received 8 July 2003, accepted 26 March 2004., Monitoring passerine population changes through counts collected along migratory routes has been attempted often (Hussell 1981, Gauthreaux 1992, Hagan et al. 1992, Hussell et al. 1992, Peach et al. 1998, [...]

We compared the definitive prebasic molt schedules of Yellow Warblers (Dendroica petechia) at two northern temperate breeding sites: the Vermont Institute of Natural Science (Vermont) in Woodstock, Vermont, and North Point (James Bay) on the southwestern coast of James Bay, Ontario. The two sites are separated by 8° of latitude. Yellow Warblers initiated molt significantly earlier in Vermont than at James Bay, with respective mean onset dates of 29 June and 20 July, but durations and rates of molt did not differ significantly between populations at the two sites. Mean individual molt durations spanned 44.5 days in Vermont and 40.0 days at James Bay. Molt rate of females differed significantly between the two sites, but male rates were similar. Based on number of primaries growing simultaneously, Yellow Warblers in both Vermont and James Bay appear to undergo a rapid and intense molt. The earlier and slightly more protracted molt of Yellow Warblers in Vermont may result from their earlier spring arrival and longer breeding season. Received 22 November 2002, accepted 11 March 2003., Migratory birds that breed in seasonally variable environments typically partition reproduction, molt, and migration within their annual cycles. Energy resource conflicts are minimized by the temporal segregation of such events [...]

Hydrogen stable-isotope analysis of feathers is an increasingly popular method for estimating the origins of migrating and wintering birds. Use of this method requires that investigators know which feathers are grown on breeding grounds and how the hydrogen stable-isotope ratios of feathers ([delta][D.sub.f]) relate to those of local precipitation ([delta][D.sub.p]). In this study, we measured [delta][D.sub.f] of adult (primaries 1, 3, and 10) and nestling Cooper's Hawks (Accipiter cooperii) in Wisconsin, North Dakota, and British Columbia, Canada. As previously shown, [delta][D.sub.f] of nestling feathers were related to [delta][D.sub.p]. In contrast, the [delta][D.sub.f] of adult feathers grown on the breeding grounds were substantially greater than those of their nestlings, and varied significantly across primary feathers and study areas. Our findings suggest that it is not possible to use hydrogen stable-isotope analysis of feathers to learn the origins of migrating adult Cooper's Hawks (or possibly adults of other large-bodied species with extended molting periods) until more is learned about the physiological or ecological mechanisms underlying these isotopic discrepancies. Key words: Accipiter cooperii, migration, molt, raptor.

The influence of the local and landscape attributes on the occurrence and density of seven passerine species in grasslands of eastern South Dakota (U.S.A.) is studied, which will help in incorporating the landscape attributes into models for migratory grassland bird conservation. The findings suggest that the multiple scales should be used for conducting assessments of regional migratory grassland bird habitats.