Intra-tropical migration and wintering areas of Fork-tailed Flycatchers (Tyrannus savana) breeding in São Paulo, Brazil

Alex E Jahn,Vanesa Bejarano,Ivan Celso Carvalho Provinciato,Marco A Pizo,Nathaniel E Seavy,Maggie Macpherson,Marcela Benavides Guzmán

doi:10.1007/bf03544339

Abstract

Fork-tailed Flycatchers ( Tyrannus s. savana ) breed from central to southern South America from September to January, migrating to northern South America to spend the non-breeding season. However, little is known of the migratory routes, rate, and timing of migration of those that breed in Brazil. In 2013, we attached light-level geolocators to breeding Fork-tailed Flycatchers breeding in Sao Paulo State. Data for six male flycatchers recaptured in 2014 indicates that they exhibited two fall migration strategies. Some individuals migrated northwest to the wintering grounds (primarily Colombia, Venezuela and northern Brazil), while others first spent several weeks in southwestern Brazil before going to the wintering grounds. Mean fall migration rate was 69 km/day (±13.7) during 59 (±13.2) days. Some flycatchers moved during winter, using more than one winter area. Flycatchers initiated spring migration in July and migrated southeast to the breeding grounds at a mean rate of 129 km/day (±19.0) during 27 (±2.8) days. A detailed understanding of the annual cycle of South America's migratory birds is essential to evaluating theoretical questions, such as the evolution of their life history strategies, in addition to applied questions, such as explanations for changes in population size, or their role as disease vectors.

Highlights

The Fork-tailed Flycatcher (Tyrannus savana) is a widespread Neotropical species, occurring from Mexico to Argentina and much of lowland South America east of the Andes Mountains, from the northern coast of the continent south to central Argentina (Fitzpatrick et al 2004, Jahn & Tuero 2013)
Little is known of the migratory routes, rate, and timing of migration of those that breed in Brazil
Results indicate that male Fork-tailed Flycatchers breeding in southeastern Brazil initiate fall migration in January or February, with some migrating directly to wintering grounds, whereas others first spend time in the region of southern Brazil, Paraguay and northeastern Argentina before migrating to northern South America

Summary

Introduction

The Fork-tailed Flycatcher (Tyrannus savana) is a widespread Neotropical species, occurring from Mexico to Argentina and much of lowland South America east of the Andes Mountains, from the northern coast of the continent south to central Argentina (Fitzpatrick et al 2004, Jahn & Tuero 2013). The Fork-tailed Flycatcher is a widespread and relatively common species in South America, decades of observations have provided few details on its migratory routes or wintering areas (Zimmer 1938, Antas 1987, Capllonch et al 2009). This is true of many other Neotropical austral migrants, which breed and migrate (typically wintering to the north of where they breed) within South America (Chesser 1995, Jahn et al 2004, Cueto & Jahn 2008). Almost all research on Neotropical austral bird migration in Brazil is in a descriptive stage, focused on answering such questions as how many migratory species there are and where they migrate (Alves 2007)

Objectives

Methods

Results

Conclusion