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The Journal of Experimental Biology 205, 503-511 (2002)
© 2002 The Company of Biologists Limited

Physiological responses of Houbara bustards to high ambient temperatures

B. Irene Tieleman1,*, Joseph B. Williams2, Frédéric LaCroix3,{ddagger} and Patrick Paillat3

1 Zoological Laboratory, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands,
2 Department of Evolution, Ecology and Organismal Biology, Ohio State University, 1735 Neil Avenue, Columbus, OH 43210, USA and
3 National Wildlife Research Center, PO Box 1086, Taif, Saudi Arabia
{dagger} Present address: Morocco Emirates Center for Wildlife Propagation, Province de Boulemane, BP47-Missour, Morocco

*e-mail: I.Tieleman{at}biol.rug.nl

Accepted 2 December 2001

Desert birds often experience a scarcity of drinking water and food and must survive episodes of high ambient temperature (Ta). The physiological mechanisms that promote survival during extended periods of high Ta have received little attention. We investigated the physiological responses of wild-caught and captive-reared Houbara bustards, Chlamydotis macqueenii, to Ta values ranging from below 0°C to 55°C, well above those in most previous studies of birds. Captive-reared Houbara bustards (mass 1245±242 g, N=7, mean ± S.D.) in summer have a resting metabolic rate (RMR) of 261.4 kJ day–1, 26 % below allometric predictions, and a total evaporative water loss (TEWL) at 25°C of 25.8 g day–1, 31 % below predictions. When Ta exceeded body temperature (Tb), the dry heat transfer coefficient decreased, a finding supporting the prediction that birds should minimize dry heat gain from the environment at high Ta values. Houbara bustards withstand high Ta values without becoming hyperthermic; at 45°C, Tb was on average 0.9°C higher than at 25°C. RMR and TEWL of captive-bred Houbara bustards were 23 % and 46 % higher in winter than in summer, respectively. Captive-reared Houbara bustards had a 17 % lower RMR and a 28 % lower TEWL than wild-born birds with similar genetic backgrounds. Differences in body composition between wild-caught and captive-reared birds were correlated with differences in physiological performance.

Key words: Houbara bustard, Chlamydotis macqueenii, resting metabolic rate, total evaporative water loss, thermoregulation, desert bird.


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© The Company of Biologists Ltd 2002