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Eye size in birds and the timing of song at dawn

journal contribution
posted on 2023-06-08, 07:41 authored by Robert J Thomas, Tamás Széskely, Innes C Cuthill, David G C Harper, Stuart E Newson, Tim D Frayling, Paul D Wallis
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.

History

Publication status

  • Published

Journal

Proceedings B: Biological Sciences

ISSN

1471-2954

Publisher

Royal Society, The

Issue

1493

Volume

269

Page range

831-837

Pages

7.0

Department affiliated with

  • Evolution, Behaviour and Environment Publications

Notes

Work with Thomas as part of his DPhil here; rest are add-ons

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2012-02-06

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