Meeting Abstract

P2.138  Wednesday, Jan. 5  Winter food limits the body condition, survival, and molt of a migratory sparrow DANNER, R.M.*; GREENBERG, R.; WALTERS, J.R.; Virginia Tech, Smithsonian Migratory Bird Center; Smithsonian Migratory Bird Center; Virginia Tech rdanner@vt.edu

Migratory animals likely encounter factors in multiple seasons and locations that ultimately affect reproductive success. For migratory birds, winter food limitation, the ability to balance energetic demands, and the development of signals that reflect that ability may affect breeding in the following summer. Food limitation may be especially acute for short distance migrants that winter in temperate zones, and often experience cold and unpredictable weather, thus likely requiring much energy for thermoregulation. We tested the hypothesis that winter food abundance limits body condition, within-season survival, annual survival, and feather molt of a short distance migratory bird, the swamp sparrow (Melospiza georgiana) on its wintering grounds in coastal North Carolina. In Winter 1, we found that birds on four similar plots had generally low body condition and low within-season survival. In Winters 2 and 3, we added food to two plots and found increases in body condition, survival, probability of molt, and extent of molt on those plots. Radio-tracking revealed very little emigration from study plots, thus supporting our survival estimates. These results emphasize the importance of winter conditions on the breeding success of migratory birds.