Bright birds make good mothers
University of York
A NERC supported study has shown that female blue tits with brightly coloured crowns are better mothers than duller birds.
The study, led by the University of York, showed that, unlike humans, birds can see ultra-violet (UV) light. While the crown of a blue tit looks just blue to us, to another bird it has the added dimension of appearing UV-reflectant.
The three-year study of blue tits, which also involved researchers from the University of California Davis, USA and the University of Glasgow, showed that mothers with more UV-reflectant crown feathers did not lay more eggs, but did fledge more offspring than duller females. These brightly coloured mothers also experienced relatively lower levels of stress hormones during arduous periods of chick rearing.
The results of the study are published in the journal Behavioral Ecology.
Author Dr Kathryn Arnold, from the University of York’s Environment Department, said, “Previous studies have shown that male blue tits prefer mates that exhibit highly UV-reflectant crown feathers. Our work shows that this is a wise choice. UV plumage can signal maternal quality in blue tits, so a male choosing a brightly coloured female will gain a good mother for his chicks and a less stressed partner.”
Funded by the Royal Society and the Natural Environment Research Council (NERC), the project was based in woodlands on the shores of Loch Lomond, Scotland and investigated the factors that affect breeding success in wild birds.
In blue tits (Cyanistes Caeruleus) both sexes exhibit bright UV-reflectant crown feathers. The birds are socially monogamous, with the female solely incubating the eggs and both parents feeding the chicks.
The researchers looked at the relative UV reflectance of the crown feathers of female blue tits and related this to indices of reproductive success - lay date, clutch size, and number of chicks fledged - as well as the birds’ maternal state.
Dr Arnold said, “With up to 14 chicks to care for, blue tit mothers in our study were feeding their broods every couple of minutes. We showed that dowdy coloured females found this level of hard work twice as stressful compared with brighter mothers. Also, the mothers with more UV-reflectant crowns were highly successful, fledging up to eight more chicks than females with drabber feathers.”
1. The article ’Ultraviolet crown coloration in female blue tits predicts reproductive success and baseline corticosterone’ by L.J. Henderson, B. J Heidinger, N. P Evans and K E Arnold is published online in Behavioral Ecology. doi:10.1093/beheco/art066.
2. Images of blue tits and a blue tit mother and chick are available by contacting the University of York press office or 01904 322029. Please credit: Vicky Ogilvie.
3. For more information visit the University of York’s Environment Department website.
4. The Royal Society is a self-governing Fellowship of many of the world’s most distinguished scientists drawn from all areas of science, engineering, and medicine. The Society’s fundamental purpose, as it has been since its foundation in 1660, is to recognise, promote, and support excellence in science and to encourage the development and use of science for the benefit of humanity. The Society’s strategic priorities emphasise its commitment to the highest quality science, to curiosity-driven research, and to the development and use of science for the benefit of society. These priorities are:
1. Promoting science and its benefits
2. Recognising excellence in science
3. Supporting outstanding science
4. Providing scientific advice for policy
5. Fostering international and global cooperation
6. Education and public engagement
5. NERC is the largest funder of environmental science in the UK. We invest £330m in cutting-edge research, training and knowledge transfer in the environmental sciences. Our scientists study and monitor the whole planet, from pole to pole, and from the deep Earth and oceans to the edge of space. We address and respond to critical issues such as environmental hazards, resource security and environmental change. Through collaboration with other science disciplines, with UK business and with policy-makers, we make sure our knowledge and skills support sustainable economic growth and public wellbeing - reducing risks to health, infrastructure, supply chains and our changing environment.
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