Eye size in birds and the timing of song at dawn

Thomas, Robert J, Széskely, Tamás, Cuthill, Innes C, Harper, David G C, Newson, Stuart E, Frayling, Tim D and Wallis, Paul D (2002) Eye size in birds and the timing of song at dawn. Proceedings B: Biological Sciences, 269 (1493). pp. 831-837. ISSN 1471-2954

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Abstract

Why do different species of birds start their dawn choruses at different times? We test the hypothesis that the times at which different species start singing at dawn are related to their visual capability at low light intensities. Birds with large eyes can achieve greater pupil diameters and hence, all other things being equal, greater visual sensitivity and resolution than birds with small eyes. We estimated the maximum pupil diameter of passerine birds by measuring the diameter of the exposed eye surface, and measured the times of the first songs at dawn of songbirds present in different bird communities, and the light intensities at these times. Using phylogenetic comparative analyses, we found that songbirds with large eyes started to sing at lower light intensities (and therefore earlier) than species with smaller eyes. These relationships were stronger when differences in body size were controlled for statistically, and were consistent between two phylogenies and when species were treated as independent data points. Our results therefore provide robust support for the hypothesis that visual capability at low light levels influences the times at which birds start to sing at dawn.

Item Type: Article
Additional Information: Work with Thomas as part of his DPhil here; rest are add-ons
Schools and Departments: School of Life Sciences > Evolution, Behaviour and Environment
Depositing User: David Harper
Date Deposited: 06 Feb 2012 20:45
Last Modified: 21 May 2012 16:17
URI: http://sro.sussex.ac.uk/id/eprint/27933
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