University of Oulu

Thermoregulatory consequences of starvation and digestion in birds

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Author: Laurila, Mirja1
Organizations: 1University of Oulu, Faculty of Science, Department of Biology
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.8 MB)
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Language: English
Published: 2005
Publish Date: 2005-05-10
Thesis type: Doctoral Dissertation
Defence Note: Academic Dissertation to be presented with the assent of the Faculty of Science, University of Oulu, for public discussion in Kuusamonsali (Auditorium YB210), Linnanmaa, on May 20th, 2005, at 12 noon.
Reviewer: Doctor Liisa Peltonen
Professor Hannu Rintamäki


In homeothermic birds and mammals, several thermoregulatory adaptations have evolved for surviving in unstable, food-restricted conditions. This study focuses on two adaptive mechanisms in pigeons (Columba livia) and quails (Coturnix coturnix japonica): hypothermia and the adaptive use obligatory heat production connected with feeding and digestion. The plasticity of the hypothermic response in fed and fasted birds and birds with restricted feeding was studied in laboratory and outdoor winter conditions. The other objective was to study adaptive timing of digestion, and substitution of facultative thermogenesis by obligatory heat production in cold and at thermoneutrality.

The results showed that fasting has a strong influence on the level of nocturnal hypothermia in laboratory conditions: hypothermia becomes progressively deeper when fasting continues. In outdoor conditions, ambient temperature and predation risk modulated the daily body temperature (Tb) pattern of fasting pigeons. In very cold conditions, diurnal Tb of fasted birds also dropped below the normal level of the active phase. Predation risk prevented diurnal hypothermia but also attenuated the depth of nocturnal hypothermia in fasting pigeons. This study provides the first empirical effects of predation risk on hypothermia in starving birds.

The study suggests that the presence of crop in pigeons allows adaptive timing of digestion. At thermoneutrality, peak digestion appeared late in the dark phase in birds with fed in the morning. Because the Tb of the birds increases to diurnal levels late in the dark phase, this obligatory heat from digestion can be used to aid re-warming by such timing. On other hand, the results of this study were partly opposite to the classical model of thermoregulatory substitution. In line with the classical model, a postprandial increase in metabolic rate (heat increment of feeding, HIF) was seen at thermoneutrality but not in cold. However, electromyographic measurements showed that there was no postprandial decrease in the intensity of shivering in the fed birds in cold. This indicates that true thermoregulatory substitution may be less common than assumed and suggests a role for facultative thermogenesis in HIF.

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Series: Acta Universitatis Ouluensis. A, Scientiae rerum naturalium
ISSN-E: 1796-220X
ISBN: 951-42-7714-7
ISBN Print: 951-42-7713-9
Issue: 435
Copyright information: © University of Oulu, 2005. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.