Breeding latitude predicts spring migration strategy of a widespread migratory bird in South America

CUETO, V.R.; MARINI, MIGUEL ÂNGELO; TUERO, DIEGO T.; JAHN, A.E,; LEVEY, D.J.; SARASOLA, J.H.; HALLWORTH, M.T.; PIZO, MARCO AURELIO

Renaissance Tuscany Il Ciocco in Lucca (Barga)

Seminario; I Gordon Research Seminar on Movement Ecology of Animals; 2019

Gordon Research Seminars

Identifying theprocesses that determine avian migratory strategies in different environmentalcontexts is imperative to understanding the constraints to survival and reproduction facedby migratory birds across the planet. We compared the spring migration strategies of Fork-tailed Flycatchers (Tyrannus savana) that breed at south-temperate latitudes (i.e., austral migrants) vs.tropical latitudes (i.e., intra-tropical migrants) in South America. Dueto a greater reproductive investment at higher latitudes in this species, we predictedthat austral migrants should migrate at a faster rate in spring, spend lesstime on stopover, and exhibit lower variation between males in the date ofarrival to the breeding area than intra-tropical migrants. We attachedlight-level geolocators to migratory Fork-tailed Flycatchers at two tropicalbreeding sites in Brazil and at two south-temperate breeding sites in Argentinaand tracked their movements until the following breeding season. Rate of springmigration did not differ significantly between the two groups and australmigrants did not stopover for less time than intra-tropical migrants. However,austral migrant males exhibited significantly lower variation in their arrivaldate to the breeding site than did intra-tropical migrant males. Thisrepresents the first comparison of individual migratory strategies amongconspecific passerines breeding at tropical vs. temperate latitudes andsuggests that spring migration strategies of birds breeding at temperate vs.tropical latitudes is molded by a different set of tradeoffs.