57.5 Saturday, Jan. 5 Food supplementation of urban and rural sparrows: effects on corticosterone, weight, and territorial aggression FOLTZ, S. L.*; DAVIS, J. E.; ROSS, A. E.; ROCK, R. P.; MOORE, I. T.; Virginia Tech; Radford University; Virginia Tech; Virginia Tech; Virginia Tech firstname.lastname@example.org
Urban areas are novel habitats that present animals with new challenges and opportunities. Our previous studies on song sparrows (Melospiza melodia) in southwestern Virginia found various physiological and behavioral differences between urban and rural populations. Specifically, urban populations often have higher baseline and post-stressor corticosterone levels, lower weight, and heightened territorial aggression relative to rural populations. Because both weight and corticosterone are related to energy balance, we hypothesized that variation in food availability between habitats may drive these observed differences. To test this hypothesis, we provided supplemental food to half of the observed territories in both urban and rural habitats. Territorial aggression was assessed by a simulated territorial intrusion in which we played previously recorded male song and observed the focal birds’ behaviors. Birds were then caught, bled, and weighed. Surprisingly, we found no effect of habitat type or food supplementation on weight or corticosterone levels. However, rural control birds were significantly less aggressive that rural fed birds and all urban birds, indicating an effect of feeding and relationship with urbanization. Our results indicate that birds were not food-limited in this study season. However, because control birds’ weight and corticosterone levels did not differ between habitats, we cannot conclude whether transient food limitation may have driven habitat-related differences observed in past years. The increased aggression of rural fed birds suggests that additional food may impact perceived territory quality or interactions with neighbors in habitat-specific ways.