Meeting Abstract

91.1  Wednesday, Jan. 7  Blackcaps use torpor and huddle while resting at a stopover site during migration. WOJCIECHOWSKI, M.S.*; JEFIMOW, M.; PINSHOW, B.; Nicolaus Copernicus University, Torun, Poland; Nicolaus Copernicus University, Torun, Poland; Jacob Blaustein Institutes for Desert Research, Ben-Gurion University, Israel mwojc@umk.pl

For small endothermic animals, daily torpor serves as an energy-saving mechanism for survival in challenging environments, and it may also accelerate fat accumulation in animals preparing for fuel-demanding activities. While monitoring body temperatures (T_b) of blackcaps (Sylvia atricapilla), freshly-caught at a stopover site in the Negev, we found that they entered shallow torpor at night, reducing T_b by 5°C, or more, below normothermic resting levels. We estimated that such reductions in T_b can lead to overnight energy savings of approximately 30% compared to birds remaining normothermic. In addition to using shallow torpor, blackcaps huddled while roosting at night, which likely represents an additional avenue for energy savings. This occurred in spring migration in the Negev Desert and in autumn migration in central Poland. Since migratory flight brings about atrophy of muscles and other organs potentially involved in thermogenesis, we hypothesize that the observed deviations from normothermy, as well as huddling at night, may be associated with decreased capacity for thermoregulatory heat production attributable to reduced organ size. Since torpor, as seen in blackcaps, may lead to significant energy savings and more rapid fuel deposition at stopover sites, we predict it to be common among small migrating passerines. This study was funded by US-Israel Binational Science Foundation grant number 2005119 to BP and Scott R. McWilliams, and by the Polish Ministry of Science and Higher Education grant number N304 048 31/1811 to MSW.