Even a mild spell of cold weather affects feeding in migrating redheaded buntings

Abstract

We investigated whether a climatic change in temperature affected daily food intake in migrating male redheaded buntings. Groups of adult male birds (n = 18) were photoinduced into migratory phenotype under increasing spring daylengths (NDL); as the birds began to exhibit night restlessness, Zugunruhe, these were allocated into groups, either with ambient (NDL, variable daily temperature: maximum – 29–44 °C and minimum – 16–33 °C; for food intake (six birds) and activity recording, six birds) until 2 weeks after they concluded migration or with constant temperature (NDT, 22 ± 1 °C; for food intake (six birds)) conditions. As day length increased March onwards, daily food intake increased (hyperphagia) in NDL and NDT groups. However, hyperphagia was slower in NDT birds as compared to NDL birds, suggesting that altered ambient temperature affects daily food intake in migrating buntings. Another group of 12 birds were held under constant daylengths (12L:12D; EDT and constant temperature 22 ± 1 °C). Although the onset of Zugunruhe was delayed under EDT, the day of onset of Zugunruhe was taken as day 0. Daily food intake and body weight before and during migration of EDT birds were compared with that of NDT and NDL groups. Daily food intake and body weight increased in all migrating birds, but hyperphagia continued post-migration in NDT birds. The study suggests that constantly suboptimal temperature despite increasing daylength, NDT, appeared to affect feeding and body weight of migratory buntings as evident from continued hyperphagia and body weight gain, even after concluding migrating activity.

Keywords:

• Emberiza bruniceps
• daily food intake
• migration
• temperature

Acknowledgement

The financial assistance from the Department of Science and Technology, New Delhi (SR/SO/AS-69/2011) to NJG is gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Department of Science and Technology, New Delhi [grant number SR/SO/AS-69/2011].