67.4 Sunday, Jan. 6 Body temperature of free-living Hoopoe Larks in Saudi Arabia WILLIAMS, JB*; TIELEMAN, BI; Ohio State Univ.; Univ. Groningen email@example.com
In endotherms, Tb is the focal point of thermoregulation, the ability of an animal to maintain its Tb within narrow limits despite changes in environmental temperature. Birds typically regulate their Tb between 38 and 41""o"" C. Although a number of cases of hypothermia have been reported in free-living birds, little attention has been devoted to variation in Tb of free-ranging birds in hot environments, nor the consequences of this variation for their water economy. We used Holohil BD2 temperature sensitive radios to monitor day-time Tb of 10 free-living male Hoopoe Larks in the desert of central Saudi Arabia during April-June, 2007. Some birds were incubating eggs, whereas others were not nesting. First we tested whether Holohil radios would provide an accurate measure of Tb over the 21 day battery-life of the radio. We placed 8 radios in physiological saline at 40 ""o""C and compared their pulse interval with temperature every 3 days for a total of 21 days. We found that these small radios drifted significantly after 12 days(>0.5""o"" C). Consequently, we implanted radios in HL and took measurements on Tb within 6 days. Tb of HL varied from a low of 40.5""o""C to a high of 44.6. This is the first study to show that a desert endotherm routinely experiences such a high Tb. During mid-day, when operative temperatures were highest, HLs used burrows of Uromastyx lizards to control Tb below lethal limits. After they entered burrows, their Tb declined at a rate of 0.22 ""o""C/min. Some HLs used shade of acacia to maintain their Tb during midday. When larks entered this shade, their Tb declined at of 0.03""o""C/min. We conclude that Hoopoe Larks have an unusually variable Tb, that their Tb regularly exceeds lethal limits for many other endotherms, and that their use of hyperthermia conserves a substantial amount of water.