Irene Tielemann University of Missouri - St. Louis, USA Title Avian adaptation to desert, tropical and temperate environments: integrating physiology, behavior, and life history Abstract The large diversity in physiological parameters, behavioral strategies and demographic variables found among endotherms of similar size has puzzled many biologists. Yet few comprehensive studies exist that explore these three components in a single system. Traditional life history theory focuses on demographic parameters, such as growth, reproduction and survival, that optimize the match between organism and environment. But the physiological and behavioral mechanisms that constitute adaptations to the environment can provide important insights in the evolutionary forces and constraints that underlie the variation in these life history parameters. Therefore, my work focuses on integrating physiology, behavior and life history when exploring how birds cope with environmental challenges. Organisms living in extreme environments provide good examples of evolutionary adaptation. With scant rainfall, low primary productivity and high ambient temperatures, desert environments combine extreme thermal conditions with a low availability of food and water for their inhabitants. Especially for birds, with their high mass-specific energy and water requirements, occupying deserts may require substantial adjustments in energy and water balance. Because energy and water are potential currencies that underlie life history trade-offs, such adjustments may have far-reaching implications for reproduction and survival of birds in deserts. The first part of my talk will focus on explaining the variation in physiology, behavior and life history of species of larks that live in habitats along an aridity gradient, ranging from hyperarid deserts in Saudi Arabia to mesic grasslands in the Netherlands. Environmental aridity is directly related to primary productivity and provides a proxy for the selection pressures that animals experience with increasing aridity, including decreasing water and food availability and increasing temperatures. In the second part of my presentation I will report on studies of the adaptations of birds to the lowland humid tropics of Panama. Here, birds show similar life history traits as in the Arabian Desert (small clutch size, slow growth, high survival), but selective pressures are markedly different, with more benign temperatures, higher humidity, increased food availability and absence of extreme seasons in the tropics compared with deserts. A key selective factor explaining the similarities and differences in the physiology-life history complexes of birds from desert and tropical environments may be the risk of disease: low in the deserts, high in the tropics. I will present some preliminary results on the immune function of birds in these different environments and try to integrate this knowledge of the immune system into previously established patterns of energetics, water balance and life history, in a three-way comparison of tropical, desert and temperate zone birds. Biography Irene Tieleman studied Biology from 1991-1997 at the University of Groningen (NL). From 1998 to 2002 she worked on her dissertation “Avian adaptation along an aridity gradient - physiology, behavior, and life history” (Advisors: Dr. S. Daan and Dr. J.B. Williams, Ohio State University). Since 2003 she is post-doctoral research fellow at the Department of Biology, University of Missouri (USA). She will be back in Groningen in 2005 as a research associate in the Animal Ecology Group of the Center for Evolutionary and Ecological Studies with a new project about “Solutions to seasonal challenges - the interplay between energetics, corticosteroid response and immune function in avian life history”. Selected recent publications Tieleman, B.I. and J.B. Williams. 1999. The role of hyperthermia in the water economy of desert birds. Physiological and Biochemical Zoology 72: 87-100. Williams, J.B. and B.I. Tieleman. 2000. Flexibility in basal metabolism and evaporative water loss among hoopoe larks exposed to different environmental temperatures. Journal of Experimental Biology 203: 3153-3159. Tieleman, B.I. and J.B. Williams. 2002. Effects of food supplementation on behavioral decisions of hoopoe larks in the Arabian Desert: balancing water, energy and thermoregulation. Animal Behaviour 63: 519-529. Tieleman, B.I., J.B. Williams, F. Lacroix and P. Paillat. 2002. Physiological responses of houbara bustards to high ambient temperatures. Journal of Experimental Biology 205: 503-511. Tieleman, B.I., J.B. Williams and M.E. Buschur. 2002. Physiological adjustments to arid and mesic environments in larks (Alaudidae). Physiological and Biochemical Zoology 75: 305-313. Williams, J.B., D. Lenain, S. Ostrowski, B.I. Tieleman and P. Seddon. 2002. Energy expenditure and water flux of Rüppell’s foxes in Saudi Arabia. Physiological and Biochemical Zoology 75: 479-488. Tieleman, B.I., J.B. Williams and P. Bloomer. 2003. Adaptation of metabolism and evaporative water loss along an aridity gradient. Proceedings of the Royal Society London B 270: 207-214. Tieleman, B.I., J.B. Williams, M.E. Buschur and C.R. Brown. 2003. Phenotypic variation of larks along an aridity gradient: are desert birds more flexible? Ecology 84(7): 1800-1815. Williams, J.B., A. Munoz-Garcia, S. Ostrowski and B.I. Tieleman. 2004. A phylogenetic analysis of basal metabolism, total evaporative water loss and life-history among foxes from desert and mesic regions. Journal of Comparative Physiology B 174: 29-39. Tieleman, B.I., J.B. Williams and G.H. Visser. 2004. Energy and water budgets of larks in a life history perspective: Is parental effort related to environmental aridity? Ecology 85(5): 1399-1410. Tieleman, B.I., J.B. Williams and R.E. Ricklefs. 2004. Nest attentiveness and egg temperature do not explain the variation in incubation periods in tropical birds. Functional Ecology 18:571-577.