Eye size and the time of arrival of birds at garden feeding stations in winter
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A nationwide volunteer survey was conducted to investigate the time at which common species of birds arrived at garden feeders in the morning during winter, and over 5,800 participants submitted observations. We examined the relationship between species’ eye size and their time of arrival at feeders, in order to investigate whether the time at which foraging was initiated was constrained by visual capability. There was a negative correlation between eye size and time of arrival at garden feeders across species, and this relationship remained significant when body mass was taken into account. This suggests that the time at which garden birds begin to forage on winter mornings may be limited by their visual capability at low light intensities.
KeywordsFeeding behaviour Eye size Visual sensitivity Garden birds
We thank all the volunteers who took part in the bird survey on the shortest day, and Graham Appleton and the staff at the Today programme on BBC Radio 4 for help with organising the survey. We would also like to thank Jeremy Greenwood for useful thoughts on how to approach the analysis, Rob Robinson and two anonymous reviewers for comments on the manuscript and Chris Thaxter for advice on phylogenetic analysis.
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