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

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