Meeting Abstract
P2-127 - Heat-induced thermoregulatory behaviors of free-living tree swallow (Tachycineta bicolor) nestlings Tsueda, SN*; Woodruff, MJ; Rosvall, KA; Indiana University, Bloomington; Indiana University, Bloomington; Indiana University, Bloomington sntsueda@iu.edu
Within the last 25 years, tree swallow (Tachycineta bicolor) populations have begun shifting further south into warmer climates, unlike many other species that are shifting north into cooler climates. Nevertheless, how tree swallows behaviorally respond to heat remains unclear. Nestlings are particularly interesting because they are undergoing a critical period of development while confined to the thermal environment of the nest cavity. Our project tests the hypothesis that nestling thermoregulatory behaviors change in response to a sudden increase in nest temperatures. To do this, nest temperatures were experimentally elevated 4°C above controls, for 4 hours, using air-activated warmers on the 12th day post-hatch. To assess experimental efficacy, we measured three temperature locations: ambient air, nest box air, and nest cup surface. We collected data from both control and experimental nests in southern Indiana, part of the southern half of the tree swallow breeding range. Nestling behavior during the second hour of experimental heat was recorded and scored. To determine how thermoregulatory behaviors are affected by the immediate environment, we then assessed the relationship between panting and temperature across the thermal gradient of the nest box. Initial analyses suggest that birds pant more as nest box air temperatures rise. We have also begun to explore how thermoregulatory behaviors may trade off with other behaviors, how heat affects space use in the box, and how these effects interact with brood size. These data further our understanding of how nestling birds respond to heat within the nest cavity.