Do migrating White-crested Elaenia, Elaenia albiceps chilensis, use stop-over sites en route to their breeding areas? Evidence from the central Monte desert, Argentina

Abstract

Very few bird species are able to complete a single long migratory flight. Instead, a far more common strategy is that birds rest and feed almost every day, accomplishing their journeys in a series of short flights. We evaluated if White-crested Elaenia (Elaenia albiceps chilensis) displays evidence of en route migratory disposition in the central Monte desert, Argentina. Recaptures and resights were lower for White-crested Elaenias than for Greater Wagtail-tyrants (Stigmatura budytoides; resident) and Southern Scrub-flycatchers (Sublegatus modestus; spring-summer visitor). The latter species showed site fidelity between years, but White-crested Elaenia did not. Percentage of individuals with cloacal protuberance was similar among the species, but individuals with brood patches were recorded only in Greater Wagtail-tyrants and Southern Scrub-flycatchers. White-crested Elaenias showed low, medium and high fat stores, while the other species presented no fat or low fat stores. White-crested Elaenia had a high level of fruit consumption, while the other species consumed fruits occasionally or not at all. Our results support the hypothesis that the White-crested Elaenia uses the Monte desert as a stop-over area during its spring flight, and yield novel insights to fill a gap in our knowledge about the annual cycle of migrant birds in the Neotropics.