“Building up body fat reserves as a safeguard against times of potential future famine is an evolved survival mechanism,” says Dr Clare Andrews, of the Newcastle University Centre for Behaviour and Evolution and one of the leaders of the study.
“What we have shown is that birds that had struggled against larger brothers or sisters for food early on were keener on finding food and tended to overeat when they became adults.”
She said the research may hold some lessons for humans.
“There’s evidence that obesity is common in people lacking a reliable supply of food,” she said. “Perhaps people too have evolved to eat more and take more interest in food if worried where their next meal will come from.”
Andrews and her colleague Professor Melissa Bateson placed smaller starling chicks in a brood with significantly larger hatchlings where they had to fight for their food. After 10 days, disadvantaged and advantaged chicks were all given lives of plenty so that it was only their “chickhoods” that differed.
Later in life, these same birds were offered a choice between feeding from easily accessible sources of crumbs and spending more time and energy foraging for crumbs hidden in sand.
Birds that had a tougher start spent more time searching for hidden crumbs despite the ready availability of alternative sources and ate more of the freely available crumbs. The birds that had an easier start, having been the largest in the nest, opted instead to take the easy pickings in moderation.
The study is published today in the journal Animal Behaviour.
Bill Condie is a science journalist based in Adelaide, Australia.
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