Doi: https://doi.org/10.13157/arla.72.1.2025.ra3
Authors: Tarso CIOLETE, Filipe C.R. CUNHA and Leonardo ESTEVES LOPES
E-mail: tarsociolete@hotmail.com
Published: Volume 72.1, January 2025. Pages 33-48.
Language: English
Keywords: body size, intra-tropical migrant, Lined Seedeater, migration and protandry
Summary:
Individual and environmental constraints play important roles in the annual arrival dates of migratory birds from their wintering grounds to the breeding grounds. In most migratory bird species, males arrive first at their breeding grounds. Experience (e.g. age) and morphometric traits that optimise flight (e.g. wing length) seem to influence an individual’s migratory schedule. To investigate the relationship between sex, age and morphometric traits on the arrival date of birds, we conducted daily monitoring of the migratory schedule of a breeding population of Lined Seedeaters Sporophila lineola, an intra-tropical migratory songbird, in south-eastern Brazil. In this small sexually colour-dimorphic species, males are territorial and can use the same territory across seasons. We were able to determine the arrival dates of 129 individuals. Overall, our findings indicated that males arrived before females in the breeding grounds (protandry). Moreover, older and larger males arrived earlier than younger and smaller males. Also, wing length correlated negatively with arrival date in males. The early arrival of males, especially older and larger ones, suggests that these individuals may be obtaining greater benefits and/or have lower costs by advancing their arrival. However, the relationship between arrival date and reproductive performance remains largely understudied in tropical systems.
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