Search

Copyright of Journal of Applied Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The tropical Andes are characterized by extreme topographic and climatic complexity, which has likely contributed to their outstanding current species diversity, composed of many range‐restricted species. However, little is known about how the distribution and abundance of highly mobile organisms, like long‐distance migratory birds, varies across different land covers, elevations, and climatic conditions within the Andes. We conducted 1,606 distance‐sampling point counts across the Colombian Andes, spanning elevations from 253 to 3,708 m, a range of precipitation regimes and representative land covers. We then employed a novel application of a multispecies hierarchical modeling approach to evaluate how elevation, local land cover, aboveground woody biomass, cloud cover, precipitation, and seasonality in precipitation shape the abundance of the migratory land bird community in the Andes. We detected 1,824 individuals of 29 species of migratory land birds, six of which were considered incidental in our study region. We modeled the abundance of the remaining 23 species, while considering observer and time of day effects on detectability. We found that both elevation and land cover had an overriding influence on the abundance of migratory species across the Andes, with strong evidence for a mid‐elevation peak in abundance, and species‐specific responses to both variables. As a community, migratory birds had the highest mean abundance in shade coffee plantations, secondary forest, and mature forest. Aboveground woody biomass did not affect the abundance of all species as a group, but a few showed strong responses to this variable. Contrary to predictions of a positive correlation between abundance and precipitation, we found no evidence for community‐level responses to precipitation, aside for a weak tendency for birds to select areas with intermediate levels of precipitation. This novel use of a multispecies model sheds new light on the mechanisms shaping the winter distribution of migratory birds and highlights the importance of elevation and land cover types over climatic variables in the context of the Colombian Andes. [ABSTRACT FROM AUTHOR]

Temporal variation in the connectivity of populations of migratory animals has not been widely documented, despite having important repercussions for population ecology and conservation. Because the long-distance movements of migratory animals link ecologically distinct and geographically distant areas of the world, changes in the abundance and migratory patterns of species may reflect differential drivers of demographic trends acting over various spatial scales. Using stable hydrogen isotope analyses (δ2H) of feathers from historical museum specimens and contemporary samples obtained in the field, we provide evidence for an approximately 600 km northward shift over 45 years in the breeding origin of a species of songbird of major conservation concern (blackpoll warbler, Setophaga striata) wintering in the foothills of the eastern Andes of Colombia. Our finding mirrors predictions of range shifts for boreal-breeding species under warming climate scenarios and habitat loss in the temperate zone, and underscores likely drivers of widespread declines in populations of migratory birds. Our work also highlights the value of natural history collections to document the effects of global change on biodiversity. [ABSTRACT FROM AUTHOR]

Migratory birds travel vast distances and the timing of migratory flights can affect survival and the ability to reproduce. For Neotropical migrant songbirds, early spring departure from wintering sites, early arrival to the breeding grounds and higher reproductive success have been related to the use of suitable habitats and environmental conditions during the non‐breeding season. However, how migratory strategies are shaped by winter habitat choice is largely unknown due to the general inability to track birds from specific wintering habitats to stopovers or breeding destinations.We assessed how winter habitat (native forest vs. shade‐grown coffee plantations) relates to spring departure date and migration pace in Swainson's Thrush Catharus ustulatus. We also determined the effect of departure date and total migration duration on the arrival date of birds detected near or within their breeding range.We used a novel application of Motus radiotelemetry arrays to track individuals from their wintering grounds in the Andes of South America along their migratory journey to North America.We found variation in migratory strategies between habitats, with birds wintering in native forest departing later than birds in coffee. We present isotopic evidence for native forest being of higher quality than shade‐coffee for Swainson's Thrush and hypothesize that moister conditions in forest, as shown by stable isotope (δ13C) analysis of thrush whole blood, provides favourable pre‐migratory conditions allowing birds to delay departure from wintering grounds. Habitat, between‐site and ‐year variation in departure date, suggests that birds made facultative adjustments to winter habitat quality and environmental conditions. Independent of habitat, birds that departed later migrated faster and this pattern was maintained along the migration route (n = 44). Migrating earlier and slower or later and faster was unlikely to result in significant differences in arrival time to breeding destinations.Our findings reveal underappreciated complexity in migratory decisions by long‐distance migrants that contrast with the current paradigm of earlier departures and arrival from optimal habitats. The next step is to understand the relative fitness benefits of early versus late schedules or whether each strategy is an equally good response to experienced conditions. [ABSTRACT FROM AUTHOR]

For migratory landbird species, large expanses of open water or inhospitable areas provide unique challenges during migration. Research on the strategies that species use to navigate barriers can yield insights into the factors shaping the evolution of migration and facilitate the identification of critical staging areas prior to barrier crossing. One such barrier, the Caribbean Sea, has received little study but must be negotiated by 50 migratory landbirds as they fly from South America to North America in spring. Recent discoveries from the gray-cheeked thrush Catharus minimus, which undertakes non-stop flights >3000 km across the Caribbean Sea, raises the possibility that the breadth of potential strategies has been unappreciated thus far. We calculated fuel load and potential flight range in 9985 individuals of 16 species captured over 10 years at two stopover sites in northern Colombia to 1) evaluate the likely migratory strategy of these species as they depart northern Colombia in spring, and 2) evaluate the influence of family, diet, morphology and migratory distance on potential flight range. We found considerable variation in flight ranges and therefore strategies for crossing the Caribbean Sea/Gulf of Mexico barrier complex. In addition to gray-cheeked thrush, non-stop flights >2500 km were possible in yellow-billed cuckoo Coccyzus americanus, yellow warbler Setophaga petechia and northern waterthrush Parkesia noveboracensis. The remaining species were either capable of over-water flights to the Yucatan Peninsula/Cuba (>1800 km) or shorter flights to middle Central America (>1000 km) and likely required one or more stopovers to reach North America. Predicted flight ranges were influenced by morphology but not by distance, diet or taxonomic group, providing a novel insight into the evolution of migratory strategies. Our study confirms the vital role northern Colombia performs in providing energy for migratory birds and highlights the Caribbean as a key migratory barrier for many species. [ABSTRACT FROM AUTHOR]

Aim: The role of migratory birds in the spread of parasites is poorly known, in part because migratory strategies and behaviours potentially affecting transmission are not easy to study. We investigated the dynamics of infection by blood parasites through the annual cycle of a long‐distance Nearctic–Neotropical migratory songbird to examine the role of this species in dispersing parasites between continents. Location: The Americas. Taxon: Grey‐cheeked Thrush (Catharus minimus, Aves, Passeriformes, Turdidae), Birds. Methods: We used molecular and microscopy screening of haemosporidian parasites (Plasmodium, Haemoproteus, and Leucocytozoon) to examine the prevalence, distribution, and diversity of lineages through the annual cycle (breeding, migration, and wintering) of the grey‐cheeked thrush in North and Central America, Santa Marta mountains, the Andes, and the Amazon. We aimed to identify transmission areas, to examine the degree of sharing of haemosporidian lineages with resident birds in various areas and to assess the potential role of immunologically naïve juvenile individuals in parasite transmission. Results: Prevalence and lineage diversity of haemosporidians varied significantly over time, being higher during breeding and fall and spring migration, and declining during wintering. Grey‐cheeked thrush shared few parasite lineages with tropical resident birds and slightly more lineages with other migratory and resident boreal species. We detected gametocytes in blood during spring migration stopover, but these were of lineages not found in resident tropical birds, indicating relapses of parasites transmitted elsewhere. Transmission likely occurs mostly on the breeding grounds, where juveniles and adults carried lineages restricted to closely related species of thrushes and other species of boreal birds. Main conclusions: Long‐distance migratory songbirds are likely not important dispersers of blood parasites because there are ecological and evolutionary barriers to the interchange of parasites across vastly separated areas. Further work with thorough spatial and temporal sampling across other species, and considering the role of vectors, is necessary to understand the ecological and evolutionary factors explaining the distribution of parasites over broad scales. [ABSTRACT FROM AUTHOR]

Aim In birds, patterns of migratory connectivity are influenced by landscape structure experienced throughout the annual cycle. Assessing how landscape patterns drive the movements and distributions of migratory species is important for understanding the evolution of migration and determining conservation priorities. We determined migratory connectivity in the Canada Warbler ( Cardellina canadensis), a declining Neotropical migratory bird, and evaluated the degree to which the Andean mountains influence winter population distribution in this montane forest specialist. Location Seven study regions across the Western, Central, and Eastern Andes of Colombia. Methods We inferred breeding and natal origins of Canada Warblers overwintering in Colombia by analysing stable hydrogen isotope values (δ2H) in feathers and assigning wintering populations to breeding origins using an established feather δ2H isoscape for North America. Results We found strong evidence for parallel migration between breeding and wintering sites, giving rise to moderately strong migratory connectivity between breeding and wintering regions. The model best explaining population distribution in the Colombian Andes implied that populations were most similar within basins or valleys. Such segregation is notable, given that basins are separated by less than 300 km on the wintering grounds, while breeding populations may be separated by more than 3000 km from east to west. Main conclusions Our results suggest that the high spine of each Andean cordillera acts to shape the winter distribution of individuals from different breeding populations. To our knowledge, this is the first demonstration that the topography of the Andean mountains can act to shape the winter distribution of populations of a migratory bird. The strength of migratory connectivity found in Canada Warblers may inhibit evolutionary responses to environmental change, and the more rapid population declines recorded in some eastern breeding populations may be related to habitat loss and local environmental conditions in the Eastern Andes, where individuals from these populations were more likely to overwinter. [ABSTRACT FROM AUTHOR]

Stopover sites used to accumulate the energy that fuels migration, especially those used prior to crossing ecological barriers, are regarded as critically important for the survival of Nearctic−Neotropical migratory birds. To assess whether South American stopover sites are used to store the energy required to cross the Caribbean Sea and the Gulf of Mexico to North America by a Neotropical migratory landbird, we studied Gray-cheeked Thrushes in northern Colombia through constant effort mist-netting during spring migration in 2010 and 2011. We combined stopover duration estimates and models of body mass change based on recaptures to estimate departure body mass and potential flight range from our study site. We recaptured 62 birds, the majority of which gained mass. Models indicated significant differences in rates of mass gain between years and age groups and with arrival date. Estimated total stopover durations varied between 15.4 (2010) and 12.5 days (2011). Predicted departure mass ranged between 41.3 and 44.9 g, and potential flight range was estimated at between 2727 and 4270 km. Gray-cheeked Thrushes therefore departed our study site with sufficient energy reserves to cross the Caribbean Sea and the Gulf of Mexico (2550 km). As the first demonstration that birds departing from South American stopover sites can reach North America without refuelling, this has important implications for stopover site protection. Strategic conservation measures in the Sierra Nevada de Santa Marta could protect habitats in which up to 40% of the energy required to complete spring migration is stored by a Neotropical migratory land bird. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study that examines the Veery or Catharus fuscescens during the 2009 and 2010 fall migrations in northern Colombia. The study shows that Veeries that arrived at the study site have low energy reserves and the body mass of recaptured birds was 3.6 percent mean rate. It also observes that birds carried energy reserves of 34 percent of loan body mass at departure.

• Measures of survival were similar between habitats. • Body condition and density were higher in forest than in coffee. • Native forest is a higher-quality winter habitat than shade-grown coffee. • Indicators of habitat quality can be misleading when density is not considered. • The conservation of forest must be a priority wherever possible. Neotropical migratory songbirds overwintering at mid elevations in the Andes of northern South America depend on remnants of native forest and shade-grown coffee plantations. The quality of such habitats is one of the primary ecological factors limiting survival of migratory birds during the non-breeding season. We assessed the relative quality of shade-grown coffee plantations vs. forest in the Colombian Andes as winter habitat for Swainson's Thrush (Catharus ustulatus). We hypothesized that native forest has a higher intrinsic value (i.e., food abundance) than shade-coffee plantations, as native forest was the original habitat for Swainsońs Thrush. We compared thrush physical condition, density, feather corticosterone values, and apparent annual survival as indicators of habitat quality in these two habitats. Measures of body condition and density were higher in forest than in shade-grown coffee, while survival was similar between habitats. This implies that forest had a higher carrying capacity than shade coffee and therefore had higher intrinsic value. Seasonal trends in body condition revealed a decline in the quality of forest with the onset of the dry season in early winter and an increase during late winter in line with increasing rainfall, suggesting that the timing of the rainy season likely offsets the negative effects of seasonal drought. Feather corticosterone levels were higher in forest, possibly as a result of a density-dependent stress response, however, we cannot rule out the effects of food availability or its distribution in space on stress levels. Our indicators suggested that native forest is a higher-quality winter habitat than shade-grown coffee. Our findings highlight how individual indicators of habitat quality can be misleading and emphasize the value of using multiple measures. While shade coffee is a critical habitat in the absence of native forest and its importance for the conservation of migratory birds is widely accepted, our results indicate that the conservation of native forest must be a conservation priority wherever possible. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]