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Stopover sites are essential to bird migration between wintering and breeding grounds, but annual variation in use and habitat conditions make it difficult to determine which sites are most critical for conservation. By studying physiological factors that may influence a bird's behavior when choosing and using a stopover site, researchers can target certain species or locations and more efficiently invest in conservation efforts. In spring 2013 and 2014, we studied stopover refueling performance in a common northeastern spring migrant, the White-throated Sparrow (Zonotrichia albicollis), at 2 locations near the south shore of Lake Ontario. We used morphological measurements and physiological techniques that assessed the concentration of the blood metabolite plasma triglyceride as a measure of fat deposition and feeding efficiency. We found that birds captured at an inland location had a significantly higher body condition score than birds captured at a coastal stopover site within 0.5 km of the shore; a trend toward higher triglyceride concentrations was also noted at the inland location. We found no significant differences in triglyceride concentrations between White-throated Sparrow color morphs, in contrast to previous studies performed during fall migration. Our results suggest that spring migrants arriving in the area in good energetic condition may begin their cross-lake journey directly from the inland site, while birds in poorer condition may 'pile up' at the lakeshore and then compete with other migrants for available resources, slowing their fat deposition rate. Our results also reinforce the importance of protecting high-quality stopover habitat where birds congregate near geographic barriers but suggest that inland habitat patches are important stopover sites that may allow some migrants to bypass nearshore areas of intense competition. Received 5 June 2017. Accepted 15 July 2018.Key words: condition, migration, refueling, stopover, White-throated Sparrow, Zonotrichia albicollis.Les sites d'escale sont essentiels a la migration des oiseaux entre les aires d'hivernage et de reproduction, mais il est difficile pour determiner des sites les plus critiques pour la conservation a cause des variation annuelles de l'utilisation et des conditions de l'habitat. En etudiant les facteurs physiologiques qui pourraient influencer le comportement d'un oiseau migrateur lors du choix et de l'utilisation d'un site d'escale, les chercheurs peuvent viser certaines especes ou endroits et investir plus efficacement dans les efforts de conservation. Au printemps 2013 et 2014, nous etudiames le ravitaillement chez un oiseau migrateur qui est commun du Nord-Est (au Canada), le Bruant a Gorge Blanche (Zonotrichia albicollis), a deux sites d'escales pres de la rive sud du lac Ontario. Nous utilisames les mesures biometriques et les techniques physiologiques pour evaluer la concentration plasmatique en triglycerides (dans le sang) comme mesure du depot de graisses et de l'efficacite de ravitaillement. Nous constatames que les oiseaux captures a un site d'escale a l'interieur des terres avaient un indice d'etat corporel significativement plus eleve que les oiseaux captures a un site d'escale cotier dans un rayon de 0,5 km de la rive ; il y avait aussi une tendance positive entre les concentrations de triglycerides et le site d'escale a l'interieur des terres. Nous ne trouvames aucune difference significative dans les concentrations de triglycerides entre les deux morphorypes du Bruant a Gorge Blanche (blanc et chamois), contrairement aux etudes anterieures effectuees pendant la migration automnale. Nos resultats suggerent que les oiseaux migrateurs qui arrivent en bon etat a ces sites d'escale au printemps pourraient commencer directement leur voyage au-dessus du lac depuis le site interieur, tandis que les oiseaux en moins bon etat peuvent << s'accumuler >> a la rive du lac et rivaliser avec les autres oiseaux migrateurs pour les ressources disponibles, par consequent ralentir leur taux de depot de graisses. Nos resultats renforcent egalement l'importance de proteger les sites d'escale de haute qualite ou les oiseaux migrateurs se rassemblent pres des barrieres geographiques, mais suggerent aussi que les parcelles d'habitat interieur sont des sites d'escale importantes qui pourraient permettre aux certains oiseaux migrateurs de contourner les zones littorales de competition intense.Mots-cles: Bruant a Gorge Blanche, condition, migration, ravitaillement, site d'escale, Zonotrichia albicollis., Migrant birds move seasonally to take advantage of plentiful resources on their summer breeding grounds while avoiding the harshest winter weather. Despite these advantages, migration may be the most dangerous [...]

Understanding full annual cycle movements of long-distance migrants is essential for delineating populations, assessing connectivity, evaluating crossover effects between life stages, and informing management strategies for vulnerable or declining species. We used implanted satellite transmitters to track up to 2 years of annual cycle movements of 52 adult female Whitewinged Scoters (Melanitta fusca (Linnaeus, 1758)) captured in the eastern United States and Canada. We used these data to document annual cycle phenology; delineate migration routes; identify primary areas used during winter, stopover, breeding, and molt; and assess the strength of migratory connectivity and spatial population structure. Most Whitewinged Scoters wintered along the Atlantic coast from Nova Scotia to southern New England, with some on Lake Ontario. Whitewinged Scoters followed four migration routes to breeding areas from Quebec to the Northwest Territories. Principal postbreeding molting areas were in James Bay and the St. Lawrence River estuary. Migration phenology was synchronous regardless of winter or breeding origin. Cluster analyses delineated two primary breeding areas: one molting area and one wintering area. Whitewinged Scoters demonstrated overall weak to moderate connectivity among life stages, with molting to wintering connectivity the strongest. Thus, Whitewinged Scoters that winter in eastern North America appear to constitute a single continuous population.Key words: Whitewinged Scoter, Melanitta fusca, population delineation, migratory connectivity, annual cycle, satellite telemetry, phenology.La comprehension des deplacements sur un cycle annuel complet d'especes qui migrent sur de longues distances est fondamentale pour delimiter les populations, evaluer la connectivite et les effets de chevauchement de differentes etapes du cycle biologique et elaborer de strategies de gestion pour les especes vulnerables ou en declin. Nous avons utilise des emetteurs satellitaires implantes pour suivre le cycle de deplacement annuel pendant jusqu'a deux ans de 52 macreuses a ailes blanches (Melanitta fusca (Linnaeus, 1758)) femelles adultes capturees dans l'est des Etats-Unis et du Canada. Nous avons utilise ces donnees pour documenter la phenologie du cycle annuel, delimiter les routes de migration, cerner les principales aires d'hivernage, de sejour, de reproduction et de mue et evaluer la force de la connectivite migratoire et la structure spatiale de la population. La plupart des macreuses a ailes blanches hivernaient le long de la cote atlantique, de la Nouvelle-Ecosse au sud de la Nouvelle-Angleterre, certaines passant plutot l'hiver sur le lac Ontario. Les macreuses a ailes blanches suivaient quatre routes de migration vers des aires de reproduction allant du Quebec aux Territoires-du-Nord-Ouest. Les principales aires de mue apres la reproduction etaient dans la baie James et l'estuaire du fleuve Saint-Laurent. La phenologie de la migration etait synchrone, quelles que soient les aires d'hivernage ou de reproduction d'origine. Des analyses typologiques ont delimite deux principales aires de reproduction, une aire de mue et une aire d'hivernage. Les macreuses a ailes blanches presentaient globalement une connectivite faible a moderee entre les etapes du cycle biologique, la connectivite entre la mue et l'hivernage etant la plus forte. Ainsi, les macreuses a ailes blanches qui hivernent dans l'est de l'Amerique du Nord semblent constituer une seule population continue. [Traduit par la Redaction]Mots-cles : macreuse a ailes blanches, Melanitta fusca, delimitation des populations, connectivite migratoire, cycle annuel, telemetrie satellitaire, phenologie., IntroductionMonitoring movement patterns of long-distance migratory animals over space and time provides insights into key aspects of their ecology (Trierweiler et al. 2014; Hallworth et al. 2015; Stanley et al. [...]

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 [...]

Numerous organisms exhibit carry-over effects, in which previous environmental conditions impact current performance. For example, reproductive output for many migratory birds can be impacted by events during the preceding migration. Lesser Scaup (Aythya affinis (Eyton, 1838); hereafter scaup) declined dramatically during 1970s-2000s, and there is evidence linking reduced reproductive output to reduced body condition during spring migration. In addition to food availability and quality, haemosporidian parasites (Plasmodium spp., Haemoproteus spp.) may be associated with condition of spring-migrating birds. We examined whether haemosporidian parasite infection status was linked to measures of size (mass, wing length, tarsus length, and keel length) and condition (body fat, size-corrected mass, wing-loading) in female spring-migrating scaup. Infection prevalence varied by year (21.7% in 2014; 47.1% in 2015) and percent body fat was negatively associated with the probability of infection. Body fat levels declined from 2014 to 2015, but at a similar rate for infected and uninfected birds. This pattern suggests that the increased prevalence in 2015 may have been related to the greater proportion of poor-condition birds being more susceptible to infection or recrudescence of latent infections. In light of forecasted range shifts and expansions of avian malaria vectors, the impact of haemosporidian parasites on migratory waterfowl condition warrants further investigation. Key words: avian malaria, Aythya affinis, blood parasite, body fat, Lesser Scaup, migration, spring condition hypothesis, waterfowl. De nombreux organismes présentent des effets résiduels, selon lesquels des conditions environnementales passées ont une incidence sur la performance présente. L'efficacité de la reproduction pour de nombreux oiseaux migrateurs peut par exemple être influencée par des évènements s'étant produits durant la migration précédente. Les petits fuligules (Aythya affinis (Eyton, 1838); appelés fuligules ci-dessous) ont connu un déclin drastique des années 1970 aux années 2000, et des indices relient une baisse de l'efficacité de la reproduction à une baisse de l'embonpoint durant la migration printanière. Outre la disponibilité et la qualité de la nourriture, des hémosporidies parasites (Plasmodium spp., Haemoproteus spp.) pourraient être associées à l'embonpoint d'oiseaux à migration printanière. Nous avons vérifié si le statut d'infection aux hémosporidies était relié à des mesures de la taille (masse, longueur des ailes, longueur du tarse et longueur du bréchet) et de l'embonpoint (graisse corporelle, masse corrigée pour la taille, charge alaire) chez des fuligules femelles à migration printanière. La prévalence d'infection varie selon l'année (21,7 % en 2014; 47,1 % en 2015) et le pourcentage de graisse corporelle présente une association négative avec la probabilité d'infection. Les pourcentages de graisse corporelle ont baissé de 2014 à 2015, mais à un rythme semblable pour les oiseaux infectés et non infectés. Ce motif donne à penser que la prévalence accrue en 2015 pourrait être reliée à la plus grande proportion d'oiseaux de faible embonpoint plus vulnérables à l'infection ou à une recrudescence d'infections latentes. À la lumière des modifications et expansions projetées des aires de répartition de vecteurs de paludisme aviaire, l'impact des hémosporidies parasites sur l'embonpoint d'espèces migratrices de sauvagine nécessite des études plus poussées. [Traduit par la Rédaction] Mots-clés : paludisme aviaire, Aythya affinis, hémoparasite, graisse corporelle, petit fuligule, migration, hypothèse de l'embonpoint printanier, sauvagine., Introduction An organism's performance at any given time is influenced by current environmental conditions, as well as previous environmental conditions that resulted in persisting changes to the organism's somatic or [...]

ABSTRACT.--Wanning temperatures have been linked to advancing spring migration dates of birds, although most studies have been conducted at individual sites. Problems may arise ecologically if birds arrive or depart [...]

ABSTRACT.--The Brown Dipper (Cinclus pallasi) was discovered to be a regular winter resident in the mountains of Verkhoyansk Range in Northeastern Siberia. This area is one of the coldest in [...]

ABSTRACT.--Global change can affect several aspects of bird biology, including population size and migration timing. We used count data collected during 25 years (1990-2014) at Hawk Mountain Sanctuary, a raptor [...]

ABSTRACT.--Throughout North America, organized groups of citizens and scientists have collected climate and bird phenology records since the 1880s. Most studies utilizing these data sets have compared mean first arrival [...]

Floodplain forest of the Upper Mississippi River is important for songbirds during spring migration. However, the altered hydrology of this system and spread of reed canary grass (Phalaris arundinacea) and emerald ash borer (Agrilus planipennis) threaten tree diversity and long-term sustainability of this forest. We estimated tree preferences of songbirds during spring migration 2010-2013 to help guide management decisions that promote tree diversity and forest sustainability and to evaluate yearly variation in tree selection. We used the point center-quarter method to assess relative availability of tree species and tallied bird foraging observations on tree species as well as recording the phenophase of used trees on five 40 ha plots of contiguous floodplain forest between La Crosse, Wisconsin and New Albin, Iowa, from 15 April through 1 June. We quantified bird preferences by comparing proportional use of tree species by each bird species to estimates of tree species availability for all 4 y and for each year separately. Species that breed locally preferred silver maple (Acer saccharinum), which is dominant in this forest. The common transient migrant species and the suite of 17 transient wood warbler species preferred hackberry (Celtis occidentalis) and oaks (Quercus spp.), which are limited to higher elevations on the floodplain. We observed earlier leaf development the warm springs of 2010 and 2012 and later leaf development the cold springs of 2011 and 2013. Yellow-rumped Warbler (Setophaga coronata), American Redstart (S. ruticilla), Warbling Vireo (Vireo gilvus) and Baltimore Oriole (Icterus galbula), and the suite of transient migrant wood warblers spread their foraging efforts among tree species in colder springs and were more selective in warmer springs. All three of the important tree species are not regenerating well on the UMR and widespread die-off of silver maple is possible in 50 y without large scale management., INTRODUCTION Migration poses many challenges for songbirds because most avian mortality may occur during migration (Stillett and Holmes, 2002), and birds en route necessarily forage and rest in unfamiliar locations [...]

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 [...]

Since the first bird observatory was established over a century ago, hundreds have been established around the world. Classic observatories share a focus on capture and study of birds in the hand, particularly migrants. Many professionals were first inspired by working at a bird observatory, and researchers have long been using observatory data and facilities in collaborative studies. Results from observatories have made major contributions to knowledge of migration: timing, routes and destinations, body condition and local movement during stopover; as well as tracking long-term population change. Nonetheless, observatories are an underutilized resource for researchers, and this paper highlights the benefits they offer and opportunities for further cooperation. Received 26 November 2015. Accepted 13 May 2016. Key words: bird observatories, cooperative studies, migration timing, routes, energetics, strategies., THE BIRD OBSERVATORY RESOURCE The term 'bird observatory' came from the English translation of 'Vogelwarte,' part of the original title of a book describing 50 years of bird study on [...]

As a small nocturnal migrant, the Northern Saw-whet Owl (Aegolius acadicus) is hypothesized to reduce predation risk by avoiding migration during the full moon. However, small-scale studies have given mixed results on whether there is a relationship between capture rate of Northern Saw-whet Owls and the lunar cycle during fall migration. We used 50 years of data from the U.S. Bird Banding Laboratory to examine capture rates of Northern Saw-whet Owls throughout North America in relation to lunar illumination. A logistic regression of 156,794 fall captures compared to random dates in the fall showed that captures are significantly less likely as lunar illumination increases. Captures at high illumination were 22% less likely than captures on moonless nights during the waning half of the lunar cycle and 41 % less likely during the waxing half of the lunar cycle. Modification of the lunar illumination index to correct for the duration of the night that the moon is in the sky gave similar results. Owls were also most likely to be captured on a Sunday or Monday, perhaps reflecting higher weekend capture effort. The relationship of captures to lunar illumination and wax/wane phase is consistent with an ultimate explanation of predator risk avoidance, but a proximate mechanism of altered owl movement is not demonstrated and alternative explanations such as variable human capture effort and changes in owls' ability to detect and avoid nets may also be responsible. Neither of our logistic models had much power, probably because local habitat and weather are strong modifiers of the lunar cycle effect on capture probability of Northern Saw-whet Owls. The average reductions calculated here may still underestimate the decrease in owl captures under local conditions of bright moonlight. Received 5 June 2015. Accepted 10 December 2015. Key words: Northern Saw-whet Owl, Aegolius acadicus, fall migration, lunar illumination, moon phase, predation risk avoidance., Most studies on moonlight and animal activity suggest that lunar cycles influence predation risks for prey and opportunities for predators (Kronfeld-Schor et al. 2013). Under normal foraging conditions, many prey [...]

While a common species throughout most of the United States, little is known on the migration habits of Red-tailed Hawks (Buteo jamaicensis). From 1999-2002, we tracked 16 adult Red-tailed Hawks from their breeding grounds in northwest Wyoming using Argos PTT transmitters. Our objectives were to identify dates and duration of migratory movements, stopover sites, and identify migration routes and wintering areas. We found the mean migration initiation date from the breeding area was 13 October, mean fall migration duration including stopovers was 23.3 days, mean distance of fall migration was 2489.6 km, and mean end date of fall migration was 5 November. Wintering locations were in Mexico and ranged from the southern Mexican state of Chiapas north to Sonora and Chihuahua. The mean number of days spent on the wintering grounds by tracked hawks was 133.1. The mean departure date from wintering grounds to breeding areas was 17 March, mean spring migration duration including stopovers was 22.1 days, mean end date of spring migration was 8 April, and mean distance of spring migration was 2 490.3 km. Most birds made stopovers during both fall and spring migration which varied in location and duration. Using satellite telemetry, we identified wintering locations of Red-tailed Hawks breeding in northwest Wyoming and confirmed a leapfrog migration pattern with no concentrated migration routes from the breeding area to non-breeding areas. Received 6 February 2015. Accepted 23 July 2015. Key words: Buteo jamaicensis, migration, migratory patterns, Red-tailed Hawk, Wyoming., The Red-tailed Hawk (Buteo jamaicensis) is a common species throughout North America (Preston and Beane 2009). Yet, our knowledge on the migratory habits of this raptor is limited. Migration count [...]

Early successional habitats are declining in eastern North America while at the same time remaining habitats are being invaded by a suite of nonnative shrub species. While the significance of these transidonal habitats to breeding birds is well known, increasing evidence suggests they are important during the postfledging/premigratory and migratory periods, not only for shrub-nesting species but also for many species that breed in latesuccessional habitats. Additionally a number of studies suggest exotic species have the potential to alter habitat quality, in turn affecting the fitness of migratory landbirds. The purpose of this study was to evaluate fitness correlates associated with migrant use of shrubland habitat dominated by nonnative honeysuckle (Lonicera spp.) in order to gauge habitat quality for spring migrants using an inland stopover site in northeastern Pennsylvania. We used estimates of mass change as our fitness indicator, with positive mass change indicating quality habitat. Our results suggest most birds gain mass while using honeysuckle-dominated habitat and many species, including species that characteristically breed in forested habitats, accrue fitness advantages from using shrubland habitat during spring stopover in northeastern Pennsylvania. However, we emphasize the need to examine the cumulative effects of exotic vegetation through multiple stages of the avian annual cycle to better understand the fitness consequences of nonnative vegetation on migratory landbirds., INTRODUCTION Transitional, early successional habitats in eastern North America are declining (Askins, 2000; Oehler, 2003; Rich et al., 2004). To date most of the concern about this loss has focused [...]

Studies of the effects of climate change on migratory bird behavior have established that many species are shifting the average day of year of their arrival at nesting sites earlier. If migrating birds are adapted to arrive at the optimum stage in the growth season to maximize the availability of resources, then migration phenology shifts may result in arrival at nesting sites at selectively disadvantageous points in seasonal development of the nesting ecosystem. First arrival dates (FAD) are changing for many species, but we know little about shifts in the corresponding accumulated growing degree units (AGDU) of arrival date in association with increasing global temperatures. By transcribing field notes for migrant arrival times during the years of 1910-1950 in the region around Fargo, ND, we obtained a detailed and robust description of historical phenological patterns. Comparison of the arrival times of 83 of the same species in the same location over the past 10 years indicate that the majority of bird species studied are arriving earlier than they did historically. The accumulated growing degree units at the time of arrival deviated from past values by as much as 4-5% higher or lower depending on the species. In general, short-distance migrants have advanced their arrival times and reduced the AGDU at the time of arrival relative to long-distance migrants. These results indicate that changing climate is influencing bird migration patterns and leading to arrival of migrants at different points in the progress of the growing season relative to the past. The impacts of this divergence on fitness and selection are expected to influence the nature of future bird communities. Received 7 March 2014. Accepted 4 September 2014. Key words: bird migration, climate change, Great Plains, growing degree units, phenology., The ability of migratory birds to maximize reproductive success in a temperate nesting environment with a finite growing season depends on their ability to mate, nest, produce offspring, and rear [...]

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 [...]

Breeding has a high energetic cost and, in central place foragers, also restricts the ability of parents for self-foraging, with affecting on their body and immunological conditions. In migratory species, breeding overlaps the period of recovery of body conditions before the following outbound migration. Those factors may reduce the breeding success and even lead parents to abandon their offspring if parental body condition cannot guarantee the success of the next migration. We studied the body and immunological conditions of a low breeding success population of Brown Skuas (Stercorarius antarcticus lonnbergi) throughout their breeding season. We evaluated changes in their body mass, blood parameters and heterophil:lymphocyte ratios (H:L), at three stages of their breeding period: Incubation, Early rearing and Late rearing. The body mass of female Brown skuas decreased during the initial stages of the breeding period and recovered towards the end. The changes in metabolites suggest a use of protein body reserves but not of lipid reserves. The H:L ratio did not indicate changes in the immune condition of the birds. Our results suggest that this low breeding success population begins its breeding period with a poor body condition that it continues to decline throughout the season. Those poor body conditions added to the need for recovery for the next migration may be the cause of the abandonment of almost totally feathered chicks. Our evidence highlights the importance of food availability, in either the breeding or wintering sites, or both, on the health of the populations of migratory top predators., Author(s): Maricel Graña Grilli [sup.1] , Marcela Pari [sup.2] , Andrés Ibañez [sup.3] Author Affiliations: (Aff1) 0000 0001 1945 2152, grid.423606.5, Grupo de Investigaciones en Biología de la Conservación, Laboratorio [...]

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.