Body surface temperature responses to food restriction in wild and captive great tits

Winder, L. A., White, S. A. , Nord, A., Helm, B. and McCafferty, D. J. (2020) Body surface temperature responses to food restriction in wild and captive great tits. Journal of Experimental Biology, 223(8), jeb220046. (doi: 10.1242/jeb.220046) (PMID:32312718)

Abstract

During winter at temperate and high latitudes, the low ambient temperatures, limited food supplies and short foraging periods mean small passerines show behavioural, morphological and physiological adaptations to reduce the risk of facing energy shortages. Peripheral tissues vasoconstrict in low ambient temperatures to reduce heat loss and cold injury. Peripheral vasoconstriction has been observed with food restriction in captivity but has yet to be explored in free-ranging animals. We experimentally food restricted both wild and captive great tits (Parus major) during winter months and measured surface temperatures of the bill and eye region using thermal imaging, to investigate whether birds show rapid local heterothermic responses, which may reduce their thermoregulatory costs when facing a perceived imminent food shortage. Our results of a continuously filmed wild population showed that bill temperature was immediately reduced in response to food restriction compared with when food was available ad libitum, an apparent autonomic response. Such immediacy implies a ‘pre-emptive’ response before the bird experiences any shortfalls in energy reserves. We also demonstrate temporal variation in vasoconstriction of the bill, with bill temperature gradually rising throughout the food restriction after the initial drop. Eye-region temperature in the wild birds remained at similar levels throughout food restriction compared with unrestricted birds, possibly reflecting the need to maintain steady circulation to the central nervous and visual systems. Our findings provide evidence that birds selectively allow the bill to cool when a predictable food supply is suddenly disrupted, probably as a means of minimising depletion of body reserves for a perceived future shortage in energy.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Nord, Dr Andreas and McCafferty, Dr Dominic and Helm, Dr Barbara and White, Dr Stewart

Creator Roles

White, S. A.: Conceptualization, Methodology, Resources, Writing – review and editing, Supervision, Project administration
Nord, A.: Conceptualization, Methodology, Validation, Formal analysis, Writing – review and editing, Funding acquisition
Helm, B.: Conceptualization, Methodology, Validation, Formal analysis, Writing – review and editing, Supervision, Project administration, Funding acquisition
McCafferty, D. J.: Conceptualization, Methodology, Validation, Resources, Data curation, Writing – original draft, Writing – review and editing, Supervision, Project administration, Funding acquisition

• Authors: Winder, L. A., White, S. A., Nord, A., Helm, B., and McCafferty, D. J.
• College/School: College of Medical Veterinary and Life Sciences > School of Life Sciences; College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: Journal of Experimental Biology
• Publisher: Company of Biologists
• ISSN: 0022-0949
• ISSN (Online): 1477-9145
• Published Online: 20 April 2020
• Copyright Holders: Copyright © 2020 The Company of Biologists Ltd
• First Published: First published in Journal of Experimental Biology 223(8): jeb220046
• Publisher Policy: Reproduced in accordance with the publisher copyright policy