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Many shorcbirds rely on sandy beaches to breed. However, these ecosystems arc rare and unstable on the Guianas coast because of sediment dynamics. Nonetheless, they host 2 shorcbirds that breed in the Nearctic and the Neotropic: Wilson's Plover (Charadrius wilsonia) and Black-necked Stilt (Himantopus mexicanus). We studied their breeding biology in the Amana Nature Reserve, a Ramsar Site in French Guiana, on sandy beaches bordered by brackish lagoons during 1 breeding season. From early June to late August 2008, we located and monitored 19 Wilson's Plover and 15 Black-necked Stilt nests. Most nests were associated with bare ground. While stilts preferred to build their nests with twigs closer to lagoons, plovers did not show any preference in nest location and composition. For plovers and stilts, clutch sizes were 2-3 eggs or 3-4 eggs per nest, respectively, and the mean egg volumes were 12.1 [+ or -] 0.4 c[m.sup.3]and 20.6 [+ or -] 0.6 c[m.sup.3], respectively. The apparent hatching success for both species was low, 11% for Wilson's Plover and 13% for Black-necked Stilt, whereas daily nest survival was high for both species. Clutch sizes, egg dimensions, and egg colorations were comparable to those described elsewhere, but the breeding season started later than at other localities for the Wilson's Plover. In French Guiana, the apparent nest success values for both species were much lower than those reported in the United States and the West Indies but seemed slightly higher than in Brazil. Human activity impacts were limited in our study area and did not explain the low nest success values found. Beach flooding at high tide was the main cause of clutch failure, followed by predation. Ironically, flooding allows the maintenance of this low, open, and debris-covered habitat used by beach-nesting shorebirds. Received 28 September 2022. Accepted 11 August 2023. Key words: breeding success, French Guiana, nest survival, sandy beaches, shorebird ecology. Beaucoup de limicoles dependent des plages sableuses pour se reproduire. En raison de la dynamique sedimentaire, ces plages sont rares et instables sur la cote des Guyanes. Neanmoins, elles abritent deux especes de limicoles nichant dans le nearctique et le neotropique: le Pluvier de Wilson (Charadrius wilsonia) et l'Echasse d'Amerique (Himantopus mexicanus). Nous avons etudie la biologie de leur reproduction dans la reserve naturelle de I'Amana, un site Ramsar en Guyane Francaise, sur des plages sableuses bordees de lagunes saumatres pendant une saison de reproduction. De debut juin a fin aout 2008, nous avons localise et suivi 19 nids de Pluvier de Wilson et 15 nids d'Echasse d'Amerique. La plupart des nids etaient associes a des sois nus. Le pluvier de Wilson n'a montre aucune preference quant a l'emplacement et a la composition des nids. Tandis que l'Echasse d'Amerique preferait construire son nid avec des brindilles plus pres des lagunes. La taille des couvees etait respectivement de 2-3 ceufs et de 3--4 ceufs par nid, et le volume moyen des oeufs etait de 12.1 [+ or -] 0.4 c[m.sup.3] et 20.6 [+ or -] 0.6 c[m.sup.3]. Le succes apparent d'eclosion etait faible pour les 2 especes, avec 11% pour le pluvier et 13% pour l'echasse, alors que la survie joumaliere des nids etait haute. La taille des pontes, la dimension et la coloration des ceufs etaient comparables a celles decrites ailleurs, mais la periode de reproduction etait plus tardive chez le Pluvier de Wilson. En Guyane francaise, les succes apparents des nids des deux especes etaient beaucoup plus faibles que ceux observes aux Etats-Unis et aux Antilles, mais ils semblaient legerement plus eleves qu'au Bresil. Les activites humaines etaient limitees sur le site d'etude et n'ont pas explique ce faible succes. La submersion des plages lors des grandes marees etait la principale cause de l'echec des pontes, suivie par la predation. Mais ces submersions ont paradoxalement participees au maintien de cet habitat bas, ouvert et couvert de debris utilise par les limicoles nichant sur les plages. Mots cles: ecologie des limicoles, Guyane francaise, plages de sable, succes reproducteur, survie des nids., The 1,600 km-long Guianas coast, located between the Amazon Delta in Brazil and the Orinoco Delta in Venezuela, has an Amazon-influenced, constantly evolving shoreline composed of shifting muddy banks and [...]

The Yellow-olive Flatbill (Tolmomyias sulphurescens) is a small insectivorous passerine inhabiting Neotropic forests. Its breeding biology is poorly known despite its abundance and conspicuousness. We describe the nesting biology of Yellow-olive Flatbills from Atlantic Forest fragments in Belo Horizonte County, Minas Gerais State, southeastem Brazil. Eighty nests were monitored every 3-5 days from August to January between 1995 and 2000. Active nests were found from mid-September through late December with a peak from mid October through late November. First clutches were usually laid during the first rains, but prior to the main peak in annual rainfall. The Yellow-olive Flatbill builds closed, pencile nests on tree branches along streams or roads, principally of dark fungal (Marasmius sp.) fibers. Clutch size ranged from two to four white eggs. Incubation was irregular and hatching was asynchronous. Incubation and nestling periods were 20 and 23 days, respectively. Nesting success across all 5 years was 29% (mean among years = 31%, CI = 25-37%), and nest predation was the main cause of nest failure (49%). Mayfield estimates of nest survival were low (mean = 26%, CI = 17-36%), and the probability of an egg to produce a fledgling was only 10%. Fledging success was 0.8 fledglings per breeding pair, and chicks fledged at 107% (CI = 106-108%) of mean adult body mass. Our results do not support the purported pattern of long breeding seasons for tropical birds. The Yellow-olive Flatbill laid unusually large clutches, had lower nest survival, and greater fledgling productivity compared with other tropical passerines. Received 28 April 2009. Accepted 23 March 2012., Studies of avian nesting biology are crucial for understanding many concepts in population biology, are relevant to evolutionary theory, and have many applications in conservation biology (Reed et al. 1998, [...]

Detailed accounts of molt and breeding cycles remain elusive for the majority of resident tropical bird species. We used data derived from a museum review and 12 years of banding data to infer breeding seasonality, molt patterns, and age and gender criteria for 27 common landbird species in northeastern Costa Rica. Prealternate molts appear to be rare, only occurring in one species (Sporophila corvina), while presupplemental molts were not detected. Most of our study species (70%) symmetrically replace flight feathers during the absence of migrant birds; molting during this period may limit resource competition during an energetically taxing phase of the avian life-cycle., Temporal patterns of molt and breeding seasonality are largely unknown for many resident tropical species (Dickey and van Rossem 1938, Snow and Snow 1964, Snow 1976) in contrast to Nearctic-Neotropic [...]

We review the published information on postnatal growth rates of hummingbirds (13 species), and report previously unpublished records for nine additional trochilid species. The allometric relationship based on the [log.sub.10]-transformed data of K (logistic growth rate constant) and body mass has a slope of -0.313 and an intercept of -0.346 (n = 22; [r.sup.2] = 0.18; P = 0.049). The allometric relationship has a slope of -0.366 and an intercept of -0.327 (n = 20; [r.sup.2] = 0.30; P = 0.013) if the two Nearctic records are excluded. Visual inspection suggests that higher K-values occur in Nearctic hummingbirds ([bar.x] = 0.422; n = 2) compared to Neotropic species ([bar.x] = 0.269; n = 20). We suggest a revival of studies collecting basic life history information such as postnatal growth rates of birds, especially of tropical taxa., The Metabolic Theory of Ecology (MTE) is a controversially debated theory related to search for nomological explanations in ecology (Brown et al. 2004). It represents a revival of allometric scaling [...]

The Reddish Scops-Owl (Otus rufescens) is a Near Threatened Sunda endemic associated with lowland closed-canopy forests. We radio-tracked the male Reddish Scops-Owl of a breeding pair in the Ayer Hitam Forest Reserve in southwestern Peninsular Malaysia from July to September 2019. From a total of 137 radio fixes, and based on its minimum convex polygon, harmonic mean, and kernel density estimations, the home range of this bird was estimated as 1.31-2.16 ha, with 2 roosts found within this area. Its movement was 39.13 [+ or -] 3.27 m h~' in the understory forest strata (1-5 m tall) and mostly close to bamboo clumps. We discuss the possible niche partitioning and interspecific interactions of this owl. Received 8 February 2021. Accepted 7 December 2021. Key words: forest disturbance, interspecific interaction, niche partitioning, primary forest, radio-telemetry. (Spanish)--El btiho Otus rufescens es un endemico Casi Amenazado de Sunda asociado con bosques de dosel cerrado de baja altitud. Por medio de radio-telemetria, dimos seguimiento al macho de una pareja reproductiva en la Ayer Hitam Forest Reserve en el suroeste de Malasia peninsular de Julio a septiembre de 2019. De un total de 137 radioposiciones, y basados en su poligono minimo convexo, media armonica y estimacion de densidad kernel, el ambito hogareno de este btiho fue estimado en 1.31-2.16 ha, con 2 donnideros encontrados en esta area. Su movimiento fue 39.13 [+ or -] 3.27 m [h.sup.-1] en el sotobosque (1-5 m de alto) y en su mayoria cerca de macizos de bambu. Discutimos la posible particion del nicho e interacciones interespecificas de este buho. Palabras clave: bosque primario, interacciones interespecificas, particion de nicho, perturbacion del bosque. radio-telemetria., Many raptors are important environmental indicators and apex predators owing to their high trophic position (Buechley et al. 2019), although knowledge gaps pertaining to their ecology hinder our understanding of [...]

It is estimated that about 80% of North American avian migrants travel along the southern coast of Texas. Quality of stopover habitat for landbirds in southern Texas is a concern, however, due to agricultural and wind energy development and increasing urbanization. Since little regional research has been conducted on stopover habitat use, we investigated habitat associations of migratory birds to identify important factors driving density along the southern Texas coast. We did this using data from landbird surveys, which took place during spring and autumn migrations from 1991 to 1993 and 2006 to 2008, within 6 land-cover types common in southern Texas. We found that oak motte had the highest density among most bird guilds. A total of 125 species of birds were detected over the course of our study and species richness was highest in oak motte and lowest in grassland. In general, land-cover types with more woody vegetation cover tended to have higher species richness and diversity than those with minimal to no woody vegetation. Although grassland ranked lowest in other metrics of bird use, it ranked highest in habitat conservation value, which accounts for species of concern. At the time of this study. Golden-winged Warbler (Vermivora chrysoplera) was the only species on Partners in Flight's Red Watch List (highly vulnerable and in need of special attention) that we observed, with recorded observations occurring in oak motte and woodland exclusively. Oak mottes are likely a prime location for species to land after flying over the Gulf of Mexico during their journey north to their breeding grounds, thus land managers that wish to provide high-quality stopover sites for migratory landbirds should preserve them. Received I January 2021. Accepted 31 May 2021. Key words: Gulf of Mexico, migratory, oak motte, songbirds, stopover. Se estima que cerca del 80% de las aves migratorias de Norte America viajan a lo largo de la costa sur de Texas. La calidad del habitat en sitios de descanso para aves terrestres en el sur de Texas es una preocupacion. en especial por Ios desarrollos agricola. de encrgia eolica y por el incremcnto en su urbanizacion. Dado que sc ha hecho poca investigation sobre cl uso de habitats de reabastecimiento. investigamos las asociaciones de habitat de aves migratorias para identificar Ios factores de importancia responsables de su densidad a lo largo de la costa sur de Texas. Lo hicimos usando datos de reconocimientos de aves. Ios cuales tuvieron lugar durante las migraciones de primavera y otono de 1991-1993 y 2006-2008 al interior de 6 tipos de cobertura del suelo que son comunes en e! sur de Texas. Encontramos que los encinares (oak mottes) tcnian la mayor densidad en la mayoria de los gremios de aves. Un total de 125 especies de aves fueron detectadas en cl curso de nuestro cstudio; la mayor riqueza de especies fue en los encinares y mas baja en los pastizales. En general, los tipos de cobertura del suelo con mas cobertura de vegetacion lchosa tendieron a tener una mayor riqueza de especies que aquellos con cobertura minima o sin vegetacion lehosa. Aunque los pastizales estaban en la ultima posicion en otras metricas de uso por aves, estas se encontraron cn la primera posicion en valor de conservacion de habitat, que considera especies con algun estatus preocupante de conservacion. En las fechas de este estudio. el chipe Vermivora chrysoptera fue la linica especie que observamos en la lista roja de Partners in Flight (altamente vulnerable y que nccesita atencion especial), con registros que obtuvimos exclusivamente en encinares y arbolados. Los encinares son sitios de primera importancia para especies que migran sobre el Golfo de Mexico y tocan tierra durante su viajc hacia el none, camino a sus areas de reproduccion, por lo que quienes manejan la tierra que deseen proveer de sitios de aha calidad para aves terrestres migratorias deben prcservarlos. Palabras clave: aves canoras, encinares, Golfo de Mexico, migratorio, sitios de reabastecimiento., Many birds in the western hemisphere breed in North America and winter in Central and South America presumably to exploit resources at their peak occurrence, requiring a bi-annual migration (Kerlinger [...]

This perspective on the stopover biology of migratory landbirds is organized around the response of migrants to challenges that can arise during stopover and how events during stopover are interconnected with other phases of the annual cycle. Landbird migrants seldom move nonstop from origin to destination, rather they stopover periodically, sometimes for a few hours, sometimes days. How well migrants meet challenges that arise during passage in a timely manner influences the success of their migration; a successful migration is measured in terms of survival and reproductive performance over the annual cycle. What transpires during migration is not isolated from other phases of the migrant's annual cycle. Events taking place in one phase carry over to affect an individual's biology in other phases, including linkage between breeding and wintering phases and the intervening migratory phase. Received 28 November 2017. Accepted 4 December 2017. Key words: annual cycle, carryover effects, migratory landbirds, stopover. Esta perspectiva sobre la biología de las aves terrestres migratorias en sus sitios de abastecimiento y descanso esta organizada en torno a la respuesta de estas aves a los retos que se presentan durante sus paradas, y cómo los eventos que acontecen durante esos periodos de abastecimiento y descanso están interconectados con otras fases del ciclo anual. Aunque en ocasiones las aves terrestres migratorias se desplazan sin parar de origen a destino, éstas prefieren hacer paradas para periodicas a veces por algunas horas, a veces por dias. El éxito de su migración es influenciado por qué tan bien y que tan a tiempo enfrenten los retos que se presentan a su paso. Este éxito se mide en términos de sobrevivencia y desempeñfio reproductive a lo largo del ciclo anual. Lo que ocurre durante la migracion no está aislado de otras fases del ciclo anual. Los eventos que tienen lugar en una fase de su ciclo anual afectan la biologiá de los individuos y son acarreados a otras fases, incluyendo la conexion que existe entre las fases de reproductión e invernada, además de lo que pasa durante la migracion. Palabras clave: Aves terrestres migratorias, ciclo anual, efecto de acarreo, sitios de abastecimiento y descanso., The benefits of intercontinental migration, regardless of whether they accrue through increased survivorship by overwintering in the tropics, increased productivity by breeding in seasonally rich temperate areas, or both, are [...]

ABSTRACT.--The purpose of this study was to assess how bird communities are grouped in vegetation types between the breeding and non-breeding seasons in two consecutive years as well as the [...]

Ground-nesting Common Nighthawks (Chordeiles minor), adapted to living and reproducing in North American cities, nest on flat-topped gravel roofs. But populations of Common Nighthawks have declined in recent years throughout their range. One hypothesis to explain these declines is that American Crows (Corvus brachyrhynchos), which have increased dramatically in numbers in urban areas in recent years, may be depredating nighthawk nests. If urban crows are a factor in nighthawk declines, we predicted there would be higher rates of predation on nests in urban areas than in rural areas. We tested this hypothesis by placing and monitoring artificial nests containing Cotumix quail eggs in both urban and rural settings. Depredation of experimental clutches was significantly lower in rural, natural habitats than in the urban environment. The type of substrate on urban roofs may also be important in influencing rates of depredation, as egg-loss was more common at experimental nests on roofs with a small pea gravel substrate than on roofs covered in larger river stone. In all cases, identified predators were American Crows. While experimental predation rates may not represent actual levels of predation on natural nests, these relative differences in rates of predation suggest that urban crows may be an important contributor to declining populations of Common Nighthawks. Received 5 December 2014. Accepted 25 December 2015. Key words: artificial nests, Chordeiles minor, Corvus brachyrhynchos, population trend, predation, urban birds., Population declines of migratory avian aerial insectivores are increasing (Bohning-Gaese et al. 1993, Nebel et al. 2010, Sauer et al. 2014). The causes of these declines remain elusive, in part [...]

From excavations at the Formative period (3,500 to 900 years old) Chiripa archaeological site on the southern shore of Lake Titicaca on the Bolivian altiplano (elev. 3,820 m), we identified 664 bones that represent 41 extant species of birds. Approximately 80% of the bones are from aquatic species such as coots, grebes, ducks, cormorants, and flamingos. Ten species from the bone sample (a grebe Podiceps occipitalis, cormorant Phalacrocorax brasilianus, goose Chloephaga melanoptera, duck Lophonetta specularoides, falcon Falco peregrinas, coots Fulica gigantea and F. leucoptera, dove Metriopelia aymara, owl Asio flammeus, and trogon Trogon personatus) were not recorded during rigorous bird surveys at Chiripa and elsewhere on the Taraco Peninsula in June-July 1996. One of these species (Trogon personatus) inhabits humid montane forest below 3,400 m elevation, and thus probably was transported by people to Chiripa from distances >80 km away. Each of the other nine species except Fulica leucoptera are known to occur regularly within the Titicaca Basin. The prehistoric data support the hypothesis that the regional composition of most continental Neotropical bird communities, in spite of many local range fluctuations, has been fairly stable over the past several millennia, a period of minor climate change compared to that of glacial-interglacial transitions. A challenge to researchers is to tease out the possible causes of local distributional changes in Neotropical birds, including an evaluation of how prehistoric people may have affected the presence and relative abundance of certain species. Received 3 September 2014. Accepted 27 February 2015. Key words: bird communities, Bolivia, Chiripa, human exploitation, long-term change, long-term continuity, zooarchaeology., INTRODUCTION South America sustains the world's richest bird communities (Stotz et al. 1996). Nevertheless, we know very little about the historical ecology of birds on this continent that is so [...]

The Sierra Nevada de Santa Marta in northern Colombia has been identified as a critical spring stopover site for at least one Neotropical migratory bird species prior to crossing the Caribbean sea on migration. The strategic location of the Sierra suggests that other South American wintering migrants may stopover there, but no information is available on the migrant community during spring or how they distribute themselves between habitats and across the broad elevational gradient. Here, we present species richness and densities of migratory landbirds obtained through standardized census and captures along an elevation gradient (100-2,100 m) covering two habitats, forest and shade coffee, during two consecutive spring migrations. The migrant community (--39 species) showed a peak in species richness and abundance at mid elevations (700-1,700 m), mirroring the pattern often observed in communities of resident Neotropical birds. However, individually the abundance of the commonest species peaked at different elevations and showed high annual variability. We also found within-species differences in density between shade-coffee and forest at the same elevation, possibly reflecting differences in habitat quality for some species. Factors such as food availability and predation risk are expected to be critical in shaping the distribution of migrants during stopover, and further research is required to identify the drivers of the observed elevational patterns. This study contributes to our knowledge of the life histories of migrants during stopover and highlights the habitats and elevations where conservation measures would protect the highest number of species and individuals at a South American stopover site. Received 31 January 2014. Accepted 5 September 2014. Key words: Colombia, density, habitat quality, montane tropical forest, shade-coffee, species richness, stopover., Nearctic-Neotropical migrants have been intensively studied on their breeding grounds, and new technologies are rapidly increasing our understanding of the connections between the different stages of their life cycles (Bowlin [...]

Flightless Cormorants (Phalacrocorax harrisi), the only flightless members of their 27-member genus, are listed as vulnerable on the International Union for Conservation of Nature (IUCN) Red List. The world population of Key words: diurnal activity, environmental factors, Flightless Cormorants, Gahipagos Islands, generalized linear models, multi-model inference, Phalacrocorax harrisi., Flightless Cormorants (Phalacrocorax harrisi), first discovered by the 1897-1898 Webster-Harris expedition (Rothschild and Hartert 1899), are large, conspicuous birds oddly overlooked by many earlier nineteenth-century expeditions to the Galapagos Islands, [...]

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 [...]

I conducted the second austral autumn raptor count at Concepcion Watch Site in the eastern Bolivian lowlands to document species composition, timing, and abundance of migrating raptors between 10 March and 6 April 2009. I counted migrants for 26 days (134.5 hrs) recording 6,979 migrating raptors of 16 species. Mississippi Kites (Ictinia mississippiensis) comprised 80% (n = 5,571), Black Vultures 11% (Coragyps atratus, n = 747), and Snail Kites 5% (Rostrhamus sociabilis, n = 396). The remaining 4% (n = 265) included 13 species and other unidentified raptors. I also recorded non-raptor species on migration from the lookout, including 36 Maguari Storks (Ciconia maguari), a flock of 11 Anhinga (Anhinga anhinga), and thousands of Barn Swallows (Hirunda rustica). My observations confirm previous records suggesting a significant raptor migration occurs at the Concepcion Watch Site in the austral autumn. Raptor monitoring should continue at Concepcion annually and the site used to promote raptor conservation and awareness in Bolivia. Received 12 December 2011. Accepted 16 April 2012., Raptor migration in South America is largely undescribed with few published papers using standardized migration monitoring protocols. This topic is understudied, but of international concern (Juhant 2011). Thirty-five raptor migration [...]

Aggression between chicks and fledglings, at times ending in siblicide and cannibalism, has been mostly studied among nest mates. It is frequent among colonial-nesting birds and is usually related to competition for limiting resources (e.g., food and space) and competitive disparities between siblings, among other factors. We report three observations of fully-grown Peruvian Pelican (Pelecanus thagus) fledglings attacking unrelated conspecific nestlings at a breeding colony in central Chile. One case ended in cannibalism. Five elements were common in all three cases: (1) nestlings that were attacked were left unattended by their parents in the nest, (2) nestlings that were attacked were newly hatched (up to 5 days of age), (3) aggressors were fully-grown fledglings (60-75 days of age), (4) aggressive fledglings always attacked nestlings in groups, and (5) all cases were observed late in the breeding season. We suggest aggression toward and cannibalism of nestlings by fledglings are opportunistic behaviors, based on the opportunity of finding unattended nests and are triggered by food deprivation, although hormonal mechanisms may also be involved. Our observations constitute the first report of aggression and cannibalism by Peruvian Pelican fledglings. Received 20 January 2012. Accepted 18 April 2012., Aggression in chicks and fledglings has been typically studied in the context of sibling rivalry (Gill 2007). Aggression may positively relate to food limitation; nest mates compete for food and [...]

We compared migrant bird recapture rate, stopover time, mass gain, and fat class between Star Island, New Hampshire and Appledore Island, Maine during spring and fall migration in relation to differences in relative species abundance between the islands; and examined potential movement of migrants between the islands. The average recapture rate in spring was 5.7% on Star Island and 3.6% on Appledore Island. Five species were recaptured more frequently on Star Island and one species more frequently on Appledore Island. There was no difference in mean minimum stopover time during spring (2.4 days on Star Island; 2.5 days on Appledore Island) and fall (2.9 days on Star Island; 3.2 days on Appledore Island). Three species had a longer mean stopover time on Appledore Island than Star Island. The island with the greater percentage of recaptures and longer stopover had more captures for a given species. Mass gains were significant for six species during spring (27.3%) and 10 during fall (38.5%) on Star Island, and five (22.7%) during spring and 13 (50.0%) during fall on Appledore Island. Five species had a difference in rate of mass gain between the islands. The between- island difference in species abundance was not reflected in between-island differences in mass gain, except for Red-eyed Vireo (Vireo olivaceus) during fall. There was no clear pattern in species differences in fat levels and differences in captures, stopover length, or mass gain between the islands. The fat-class and mass-gain results suggest habitat use, as measured by relative abundance, is not based on the ability to gain mass at the time of stopover. The notable fall mass gains for Red-eyed Vireo illustrate the availability of food resources for some species on both islands. Only 42 of 10,437 migrant birds banded moved from one island to the other. There was little evidence of movement between islands in a seasonally-appropriate direction for continued migration, or evidence indicating a shift between islands after initial capture. Received 21 April 2010. Accepted 11 November 2011., Stopover sites provide migrants with an opportunity to replenish critical energy supplies (Moore et al. 1995), reorient (Baird and Nisbet 1960), escape adverse winds and weather, recover from muscle fatigue [...]

The narrowing of the North American continent at the Isthmus of Tehuantepec creates an important geographic bottleneck for songbirds on their northward spring migrations. The Sierra de Los Tuxtlas, in the northwestern portion of the Isthmus, provide an ideal location from which to address questions of resource use and fuel acquisition during migration. We operated mist nets during morning and evening to capture passerines during spring migration in 2003 and 2004. Seven of 13 taxa had significant diurnal increases in body condition (an index of size-adjusted mass): Swainson's Thrush (Catharus ustulatus), Wood Thrush (Hylocichla mustelina), Magnolia Warbler (Dendroica magnolia), Kentucky Warbler (Oporornis formosus), Hooded Warbler (Wilsonia citrina), Worm-eating Warbler (Helmitheros vermivorum), and Ovenbird (Seiurus aurocapilla). All of these species, except Ovenbird, also had a significant increase in fat score. Indigo Buntings (Passerina cyanea) had a significant increase in fat score but not in condition index. A comparison with autumn migration at this site showed overall similarities in percentage of species gaining mass and in the amount gained, but there were seasonal differences within species. There was no relationship between increase in body condition and a mainland versus trans-gulf migratory strategy. Received 13 November 2007. Accepted 19 March 2011., Migration places intense physical demands on birds. One of the main adaptations enabling birds to make long-distance seasonal migrations is fat deposition (Blem 1990, Rogers 1991). Food resources at stopover [...]

Search behavior of arboreal insectivorous migrants was studied at three stopover sites along the northern coast of the Gulf of Mexico during spring migrations, 1993-1995. We examined if search behavior was affected by phylogeny, or by environmental factors. A sequence of search movements (hop, flutter, or flight) in a foraging bout was recorded for each migrant encountered. Search rate, frequency, and distance of movements were calculated for each species. Search rate was positively correlated with proportion of hop, but negatively correlated to flight distance. Hop distance was positively correlated to tarsus length, as was flight distance to wing length for the 31 species of migrants. Cluster analysis indicated closely related species generally have similar foraging modes, which range from 'sit-and-wait' of flycatchers to 'widely foraging' of warblers. Migrants tended to use more hops in dense vegetation, but more flights in areas with sparse vegetation. Migrants also used more flights when foraging in mixed-species flocks and during periods of high migrant density. Logistic models indicated warblers were more influenced by environmental factors than vireos, possibly because warblers are near-perch searchers and more affected by these factors. Received 6 May 2010. Accepted 17 December 2010., Numerous studies have reported on the search behavior of forest birds (Williamson 1971; Morton 1980; Fitzpatrick 1981; Robinson and Holmes 1982, 1984; Holmes and Recher 1986; Hutto 1988; Lovette and [...]

We compared the distribution of migrant bird species between two islands in the Gulf of Maine to examine if differences in habitat resulted in differences in avian species composition and relative abundance during stopover. Ninety-one species were captured on both islands and those species captured on only one island were either breeding species or rare visitors to the islands. Differences in bird species distribution between islands were species-specific and consistent among sampling periods for nearly all species. Twelve species were captured more frequently on Star Island and 11 species more frequently on Appledore Island. Stopover species distribution appeared to be related to habitat structure, vegetation, diet, and habitat area. Scrub-shrub/open habitat breeding species and forest breeding species were not evenly distributed between islands. Island use was most closely associated with breeding habitat. All but two of the eight species that breed in scrub-shrub or open habitat were captured more frequently on Star Island. Ten of the species more common on Appledore Island breed in forested habitat. Nine of the 11 species more common on Appledore Island are area- sensitive in breeding areas, suggesting potential area sensitivity during migration. Differential habitat use indicates a large number of stopover sites in a wide variety of habitats are necessary to meet migration needs of passerine species. Received 17 November 2006. Accepted 22 April 2010., Suitable stopover habitat is critical to a successful migration (Moore et al. 1995) and loss of stopover habitat may be a factor in long-term population declines (Sherry and Holmes 1995, [...]

We investigated avian use of clearcuts and two-age harvests during the post-breeding period in 2006 in the central Appalachians, West Virginia, USA with an information-theoretic approach to model selection. Cover variables appeared to be most important; e.g., vegetative vertical complexity had a strong positive relation with capture rates of mature forest birds and molting adults, as well as physical condition which supports a predator-avoidance hypothesis for habitat use. Basal area was a poor predictor of captures; residual trees near nets tended to depress capture rates. Food variables best explained capture rates for some species groups (e.g., early-successional insectivores and granivores, mature forest nesting adults, molting birds), but post-breeding habitat quality was based primarily on vegetative cover. Habitat use may depend on the bird's physical condition and molt status, and we found evidence for age-specific differences which may impact survival. Our study suggests important links between post-breeding habitat quality, molt status, physical condition, and bird age, and indicates a variety of response variables (relative abundance, survival, body condition) should be measured to assess avian habitat quality during the post-breeding period. Received 19 March 2009. Accepted 6 February 2010., Recent declines in populations of migratory birds that nest in both mature forest and early-successional habitats have stimulated interest in limiting factors and potential mortality sources throughout the year (Robbins [...]

The Llanos is a significant waterbird site in the Western Hemisphere, but abundance and distribution of waterbirds across this vast region are poorly known, which hampers conservation initiatives. We used point counts along road routes in the Llanos region of Venezuela to examine abundance and distribution of waterbirds during 2000-2002 within five ecoregions across the Llanos. We detected 69 species of waterbirds and recorded 283,566 individuals, of which 10 species accounted for 80% of our observations. Wading birds (Ciconiiformes) represented the largest guild both in numbers of species (26) and individuals (55%), followed by waterfowl (26%), and shorebirds (11%). Five species comprised 62% of all individuals: Cattle Egret (Bubulcus ibis), White-faced Whistling Duck (Dendrocygna viduata), Blackbellied Whistling Duck (D. autumnalis), Great Egret (Ardea alba), and Wattled Jacana (Jacana jacana). Wading birds were particularly ubiquitous with at least 21 of 26 species recorded in each of the ecoregions. Species richness (66), proportion of waterbirds detected (54%), and mean number of birds per route (1,459) were highest in the Banco-Bajio-Estero savanna ecoregion. Our study provides the most comprehensive data set available on waterbirds in the Llanos of Venezuela and highlights regions of special conservation concern., The Llanos is the second largest savanna ecosystem in South America after the Cerrado of Brazil, covering some 451,474 [km.sup.2] of which two-thirds occur in Venezuela and the remainder in [...]

I examined the temporal pattern of migration and tree species preferences of Yellow-rumped Warblers (Dendroica coronata) in relation to tree and food phenology across three spring seasons (2001-2003) at a migration stopover site in east-central Illinois, USA. Foraging Yellow-rumped Warblers used tree species in relation to the date that trees initiated bud break and the date caterpillars were most abundant in trees. The first arrival date of Yellow-rumped Warblers at the stopover site varied with date of bud break; duration of migration through the stopover site ranged from 31 to 47 days. The earliest Yellow-rumped Warbler migrants observed arrived at the stopover site before appearance of many arthropods, and foraged on the temporarily abundant adult stage of the hackberry psyllid (Pachypsylla spp. [Fletcher] [Homoptera]). Later migrants switched to foraging for caterpillars. The proportions of foraging observations among tree species were similar across all 3 years and, each year, tree species used by Yellow-rumped Warblers diversified as spring progressed. Yellow-rumped Warblers are short-distance migrants (most winter in the southern United States); my results indicate these birds may have an advantage over long-distance migrants in view of global climate change as they can arrive early at stopover habitats and exploit resources when they are most available., Global climate change has affected the phenology of many biological events (Root et al. 2003, Parmesan 2006, Rosenzweig et al. 2008). Long-term data over the last 40-100 years in Europe [...]

Little is known about how landbirds use urban habitats as migratory stopovers despite increasing urbanization in North America and the importance of the migratory period to annual survival of birds. I examined 15 years of autumn stopover data for three species of migratory Catharus thrushes from an urban natural area in metropolitan Detroit, Michigan, USA. The majority of birds were in good condition on first capture with 59% having more than a just a trace of fat, a higher proportion than reported for passerines at other fall stopover sites. Condition was similar among species, and there was little difference in fat class or mass between age groups. A linear regression of the condition of each bird at first capture and time of capture indicated positive diurnal mass gains in two species and mass loss in the third. Fourteen percent of thrushes banded were recaptured. Lean birds were not more likely to be recaptured than fatter birds and, among recaptured birds, there was no difference in stopover period or mass or fat increases between young and adults. Seventy-nine percent of recaptured birds gained mass, and mass and fat class increases were significant for all species. These results are discussed in view of the high prevalence of non-native fruit resources and rates of human disturbance at the study site., There are no published long-term studies of stopover ecology of migrant birds in urban natural areas, even as birds are increasingly encountering such sites during migration. Habitat lost to urbanization [...]

Swainson's Warbler (Limnothlypis swainsonii) is a species of conservation concern because of its small wintering range in the Caribbean Basin, relatively low population densities, and habitat fragmentation in its core breeding range in the southeastern United States. We investigated microsatellite DNA variation among 11 breeding populations from eastern Texas to Virginia and two populations from wintering areas in Jamaica and Mexico. Analyses of six polymorphic loci indicated a moderate level of gene flow among breeding populations, relatively small effective population sizes (, Genetic differentiation in migratory species is often associated with migratory divides where populations that winter in different regions meet during the breeding season in parapatric contact zones (Salomonsen 1955). Studies [...]

The Canada Warbler (Wilsonia canadensis) is currently in decline in the northeastern United States and basic demographic parameters remain to be described. We studied marked populations (76 ASYs, 14 SYs, and 2 of unknown age) of Canada Warblers on two study sites from 2003 to 2006. We mapped 92 territories (including males returning in multiple years) of 71 males using handheld GPS and ArcMap. We compared the pairing and fledging success of older and younger males on both sites, a red maple (Acer rubrum) swamp and a young forest intensively harvested in 1985 with ~10% residual standing trees used by males as song perch trees. Both sites had a high proportion of ASYs (84% ASY for all territorial males, 77.5% of all males including non-territorial individuals). Both pairing (91%) and fledging (78%) success was comparatively high suggesting these two sites were of high value to this species. A higher proportion of SYs were transients. Pairing success was lower for younger males which established territories, but paired SYs fledged at least one young at a rate comparable to older males. This study corroborates the benefits of age and experience to reproductive performance. The results suggest that both red maple swamps and post-harvest forests with thick subcanopy vegetation and emergent trees provide high quality habitat for breeding Canada Warblers., Demographic studies are important in understanding the population ecology of a bird species, especially during the breeding season. A bird's age can greatly affect its ability to hold high quality [...]

We measured rates of mass change of eight species of migratory passerines in a New York City park during three consecutive spring and autumn migrations to evaluate the quality of an urban habitat as a stopover site. We also examined seasonal differences in body condition. Linear regressions of a condition index on time of day detected significant hourly mass gain by Magnolia Warbler (Dendroica magnolia), Black-throated Blue Warbler (D. caerulescens), Ovenbird (Seiurus aurocapilla), and Northern Waterthrush (S. noveboracensis) during spring, and Common Yellowthroat (Geothlypis trichas) during autumn. Swainson's Thrush (Catharus ustulatus) showed significant mass loss during autumn. Significant spring mass gain rates ranged from 0.99 to 2.46% of mean body mass/hr. Common Yellowthroat gained 1.28% of mean body mass/hr during autumn. Most species were heavier and fatter in spring than autumn. The significant mass gain rates were comparable to those in similar studies in more pristine areas. Our results suggest the urban stopover site we examined is a place where migrants can sufficiently replenish energy stores. This highlights the importance of conserving and properly managing remaining green spaces in urban areas along major migratory bird flyways., Nearctic-neotropical migratory passerines engage in episodes of intense exercise during nocturnal migratory flights followed by periods of hyperphagia and rapid fat deposition during stopovers. Stopover habitats in which depleted energy [...]

The Black-faced Hawk (Leueopternis melanops) and White-browed Hawk (L. kuhli) are forest-based, Amazonian raptors whose distributions have been considered to be mutually exclusive north and south of the Amazon River, respectively. The occurrence of L. melanops south of the river was first indicated by a specimen collected by A. M. Olalla on the lower Tapajos River >70 years ago. The provenience of this specimen has been contested by diverse authors but both species were recently captured at localities along the lower Tapajos, corroborating the coexistence of L. melanops and L. kuhli in this region. We present four new specimen localities for L. melanops in southern Amazonia, greatly amplifying its known distribution. We also describe the immature plumage of L. kuhli based on three specimens that had been identified as L. melanops., The genus Leucopternis comprises 10 forest hawk species distributed from southern Mexico to northern Argentina and Uruguay. Six occur in Brazil: White Hawk (L. albicollis), Slate-colored Hawk (L. schistaceus), White-browed [...]

We conducted mist netting each October from 1994 to 2004 on Guana Island, British Virgin Islands, and recorded bird sightings to develop a more complete inventory of the island's resident and migrant species. During our study, we recorded four new species for the British Virgin Islands: Magnolia Warbler (Dendroica magnolia; 1996), Golden-winged Warbler (Vermivora chrysoptera; 1997), Swainson's Thrush (Catharus ustulatus; 2000), and Red-necked Phalarope (Phalaropus lobatus; 2004). Blackpoll Warbler (Dendroica striata) was the most frequently captured Neotropical migrant landbird, despite only being first detected in the region in 1989. Captures and detections of other Neotropical migrant landbirds suggest that many species may be more common in the region than previously believed, or, as speculated by other researchers, that migrant routes may be shifting eastward due to habitat degradation on western Caribbean islands. We also used recapture data to establish longevity records of resident species, including Caribbean Elaenia (Elaenia martinica; ≥ 7 years), Bananaquit (Coereba flaveala; 7 years), Black-faced Grassquit (Tiaris bicolor; ≥ 9 years), and Zenaida Dove (Zenaida aurita; 5 years). Longevities of other resident species were similar to, or slightly less than, those reported elsewhere. Received 22 February 2005, accepted 30 November 2005., Ornithological research conducted in the West Indies has covered an array of topics, including avian species occurrence and distribution, ecology of individual species, effects of hurricanes on island bird populations, [...]

THE BIRDS OF PANAMA: A FIELD GUIDE. By George R. Angehr and Robert Dean. Zona Tropical/Cornell University Press, Ithaca, New York, USA. 2010:456 pages. ISBN: 978-0-80147674-7. $35.00 (paperback).--On a natural [...]

RAPTORS OF THE WORLD: A FIELD GUIDE. By James Ferguson-Lees and David Christie. Princeton University Press, Princeton, New Jersey, USA. 2005:320 pp., 16 figs., 118 plates, and 7 tables. ISBN: [...]