Meeting Abstract

P3.211  Tuesday, Jan. 6  Metabolic performance and latitudinal distribution of Black-capped and Carolina Chickadees OLSON, JR*; SWANSON, DL; COOPER, SJ; BRAUN, MJ; WILLIAMS, JB; Ohio State Univ., Columbus; Univ. of South Dakota, Vermillion; Univ. of Wisconsin-Oshkosh; Smithsonian Institution, Suitland, MD; Ohio State Univ., Columbus

In endotherms, metabolic performance affects a wide array of ecological traits, including species distribution, and researchers have suggested that the northern boundaries of North American passerines are limited by birds ability to sustain high metabolic rates required for thermoregulation. Black-capped chickadees (Poecile atricapillus, BC) are year-round residents in most of Canada and the northern United States, while Carolina chickadees (Poecile carolinensis, CA) inhabit the southeastern United States. These species hybridize along a narrow contact zone that is moving north at approximately 1.6 km per decade, movement possibly facilitated by global climate change. There is strong evidence that the chickadee hybrid zone is correlated with temperature, as the east-west orientation closely matches temperature isotherms. We measured basal (BMR) and peak metabolic rates (PMR) for BC and CA in multiple states and also obtained metabolic rates for additional populations in previously published studies. We noted a general correlation between colder temperatures and higher metabolic rates among populations of BC, although this trend was not robust between all locations. Metabolic rates of CA did not differ between populations. Within Ohio, BMR and PMR were significantly greater in BC than CA. However, metabolic rates did not differ between the two species after controlling for the effect of mass. Hybrids had a significantly higher mass-specific BMR than either parental species. We suggest that the mtDNA-nDNA mismatch in hybrids may produce defective metabolic proteins, increasing metabolic rate because individuals rely on a greater rate of oxygen consumption to meet ATP demands.