Journal
ZOOLOGY
Volume 112, Issue 2, Pages 128-138Publisher
ELSEVIER GMBH
DOI: 10.1016/j.zool.2008.05.001
Keywords
Pelagic seabirds; Foraging segregation; Natural selection; Sexual selection; Geometric morphometrics
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Funding
- Ministerio de Educacion y Ciencia (MEC) of Spain
- Fundacao para a Ciencia e a Tecnologia (FCT), Portugal [SFRH/BD/28565/2006]
- MEC
- Fondos FEDER
- [REN2002-01164/GLO]
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The bill is a sexually dimorphic structure in many bird species and implicated in numerous functions. Sexual differences may arise from sexual selection or ecological divergence. Here, we examined differences in bill size and shape between males and females and explored to what extent these relate to feeding ecology of each sex in Cory's shearwater (Calonectris diomedea). We applied linear measurements and geometric morphometric methods to examine sexual differences in bill size and shape. We investigated feeding ecology by tracking foraging movements during the breeding period and by analysing stable isotope signatures in blood during the breeding period and in feathers grown during the non-breeding period. Bill traits were all sexually dimorphic, both in absolute and relative terms, and scaled hypermetrically with body mass in several characters in males. However, males and females did not differ in their feeding areas or isotopic signatures and no significant correlation was observed between these traits and bill dimorphism. Therefore, we discard the foraging-niche divergence hypothesis, and suggest that sexual dimorphism in bill size in this species is more likely driven by sexual selection related to antagonistic interactions. (C) 2008 Elsevier GmbH. All rights reserved.
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