Abstract
Migratory animals often play key ecological roles within the communities they visit throughout their annual journeys. As a consequence of the links between biomes mediated by migrants, changes in one biome could affect remote areas in unpredictable ways. Migratory routes and timing of most Neotropical austral migrants, which breed at south temperate latitudes of South America and overwinter closer to or within tropical latitudes of South America, have yet to be described in detail. As a result, our understanding about how these birds provide links between South American biomes is almost non-existent. White-crested Elaenia (Elaenia albiceps chilensis) is a long-distance austral migrant that breeds in the Patagonian Forest biome and overwinters in tropical South America. Because this small flycatcher plays a key role in the regeneration of this ecosystem, our objective was to describe the annual cycle of White-crested elaenias to evaluate the degree of migratory connectivity between breeding and wintering areas and therefore to determine if there are specific biomes of northern South America linked by elaenias to Patagonian forests. Fifteen individuals were successfully tracked throughout a complete migration cycle using miniature light-level geolocators. All individuals resided and moved through the same general regions. During fall (March-April-May), elaenias were located in the Caatinga and the Atlantic Forest biomes, from Rio de Janeiro to the region near Salvador da Bahia, Brazil. During winter (June-July-Aug.), birds were located further inland, within the Cerrado biome. Birds used three different routes during fall migration. Our results indicate that some individuals use a direct route, flying between 500–600 km/day, crossing desert and grasslands, while others took a detour, flying 100–200 km/day through forested areas with refueling opportunities. All birds used the Yunga forest during spring migration, with ten out of 15 individuals showing a clear counterclockwise loop trajectories throughout their annual cycle. None of the elaenias passed through Amazonia, traveled to western South America or crossed the Equator. Eleanias exhibited a high migratory connectivity between breeding area in Patagonian Forests and winter areas, Atlantic Forest and Cerrado. Our results suggest that Patagonian Forests could be strongly impacted by changes in those biomes or in the Yungas.
Highlights
Research on animal migration has focused on how, when, where, and why animals migrate [1]
Our objective was to describe the annual cycle of the White-crested Elaenia, determining migration routes, rate and dates of migration, and wintering areas, to evaluate the degree of migratory connectivity between breeding and wintering areas
All elaenias studied returned to the breeding area in Argentina along the same route
Summary
Research on animal migration has focused on how, when, where, and why animals migrate [1]. Migration studies have focused on the role of migrants in the communities visited. Given the potential of migrants to link distantly separated communities, ecological processes in one location cannot be viewed in isolation [2]. Migrants function as "mobile links" in community networks, and are essential components for ecological resilience [3]. The strength of interactions produced by migrants can be predicted based on the frequency and duration of their presence at a given site, the resources they consume, and abundance and diversity of other species with similar functional roles [2]. As a consequence of the links between biomas mediated by migrants, changes in one biome could affect remote areas in unpredictable ways [2, 3]
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