Environmental News Network - Small Birds Almost Overheat While Feeding Their Young

Details: By Lund University; 16.May

For decades, researchers have thought that access to food determined the brood size of birds. Now, biologists at Lund University in Sweden have discovered a completely new explanation: the body temperature of small birds can increase by more than 4°C to exceed 45°C when they are feeding their young. Larger broods would require more work, resulting in even higher body temperatures - something the birds would probably not survive.

Julie Swatson

For decades, researchers have thought that access to food determined the brood size of birds. Now, biologists at Lund University in Sweden have discovered a completely new explanation: the body temperature of small birds can increase by more than 4°C to exceed 45°C when they are feeding their young. Larger broods would require more work, resulting in even higher body temperatures - something the birds would probably not survive.

“A body temperature of over 45°C must be close to fatal even for small birds”, says Jan-Åke Nilsson, professor at Lund University.

Small birds, passerines, normally have a body temperature of around 41°C. Jan-Åke Nilsson and his colleague Andreas Nord studied marsh tits, discovering that their body temperature increased considerably as they worked hard, for example when feeding their young.

Flying back and forth to the nest means they do not get the opportunity to get rid of excess heat, resulting in a higher body temperature.

In addition, the study shows that the tits’ body temperature follows the surrounding temperature. When the weather is warm, the birds’ body temperature increases.

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Small Birds Almost Overheat While Feeding Their Young