Sexy birds: why females prefer males with red beaks
1 April 2003
Nine out of ten female zebra finches prefer males with the reddest beaks, according to new research findings. Not only are these males more attractive, they are also healthier.
The study, led by Dr Jonathan Blount of Glasgow University, is featured in the latest issue of Science (published 4 April) and was funded by the Swindon-based Natural Environment Research Council.
Dr Blount's team set out to discover why the more colourful males had the most luck with the ladies. Their research has shown that these males have far better immune systems than finches with less extravagant displays of colour. So picky females are more likely to get a healthier mate.
The scientists varied the finches' food intake of carotenoid pigments, the naturally occurring nutrients that are responsible for the red, yellow and orange coloration patterns in animals and in foods such as carrots. They measured the effects on beak colour, sexual attractiveness and the immune system. They found that the male zebra finches that ate more carotenoids developed redder beaks and became more sexually attractive to the females. These males also had substantially enhanced immune defences.
"Carotenoids are more than just colourful pigments - they are used in the body to neutralise harmful free radicals and to stimulate the immune system," explains Dr Blount. "Until now it hasn't been clear whether all of these birds have sufficient carotenoids to maintain their sexual attractiveness and at the same time keep their immune system in top working order. Our research suggests that this isn't the case – only those males with fewest parasites and diseases are likely to be able to devote sufficient carotenoids to their appearance to produce the best sexual display."
A number of additional factors are known to influence the ability of animals to obtain carotenoids and use them to enhance sexual displays. These include foraging efficiency, the effects of parasites in the gut and the amount of energy needed to convert the carotenoids into a usable form.
Dr Blount adds, "While beak colour is not the only signal female zebra finches consider when selecting a mate it's now clear that a male's carotenoid levels, and therefore attractiveness, are linked to the effectiveness of his immune function."
Given that carotenoids are found in a variety of foods, maybe men should start investing more in carrots and less in flashy cars and designer gear...
Further information
NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215
Dr Jonathan Blount
University of
Glasgow
Tel: 0141 330 4954
Judith Hodgson
Press Officer
University
of Glasgow
Tel: 0141 330 3535
Notes
1. Jonathan Blount, University of Glasgow, leads the research for this study. Others in the research team are: Neil Metcalfe, University of Glasgow, Tim Birkhead, University of Sheffield, and Peter Surai, Scottish Agricultural College.
2. Filming and photography of the finches can be arranged via the University of Glasgow press office, Tel: 0141 330 3535
3. Images attached: Please credit Tim Birkhead, University of Sheffield. For use on websites, permission must be obtained from Tim Birkhead, Tel: 0114 222 0002 / 4779.
4. NERC leads in providing independent research and training in the environmental sciences.
Press release: 05/03
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