The Wilson Journal of Ornithology 122(2):378–380, 2010 Thermoregulatory Behavior in Migratory European Bee-eaters (Merops apiaster) Reuven Yosef 1 ABSTRACT.—Birds in hyper-arid environments have acute problems of energy and water balance, and thermoregulate both physiologically and behaviorally. I report on European Bee-eaters (Merops apiaster) engaged in a previously unreported thermoregulatory behavior of diving into the sea and in salt ponds with high levels of salinity. This behavior may also explain the previously reported, but unexplained, finding of bee- eaters inside a tiger shark (Galeocerdo cuvier) in the Red Sea. These observations should instigate future experiments on the subject of selective use of salt water for evaporative cooling and thermoregulatory behavior by desert birds. Received 27 August 2009. Accepted 9 December 2009. Animals in deserts use a variety of mechanisms to maintain their body temperature within phys- iologically acceptable limits and minimize water loss (Louw and Seely 1982). Heat stressed birds engage in panting or gular fluttering to affect evaporative cooling (Tieleman 2002, pers. obs.). Other physiological adaptations in hot environ- ments include greater tolerance of tissues to high temperatures and dehydration, heterothermy (fluc- tuation of body temperature in response to environmental stress), reducing insulation, and appropriate coloration (Louw and Seely 1982, Maclean 1996, Tieleman 2002). Behavioral thermoregulation is a suite of behavioral activities that minimize the exposure of the organism to heat stress and reduce water loss at high temperatures (Wunder 1979). It is The Wilson Journal of Ornithology wils-122-02-18-29.3d 10/3/10 16:46:20 378 Cust # 09-110 1 International Birding and Research Centre in Eilat, P. O. Box 774, Eilat 88000, Israel; e-mail: ryosef@eilatcity.co.il 378 THE WILSON JOURNAL OF ORNITHOLOGY N Vol. 122, No. 2, June 2010