Meeting Abstract

54.9  Tuesday, Jan. 6  Protein requirements of seasonally frugivorous songbirds decrease during migration LANGLOIS, L.; MCWILLIAMS, S.**; Univ of Rhode Island; Univ of Rhode Island srmcwilliams@uri.edu

Many songbirds are seasonally frugivorous in that they switch to eating primarily fruit during migration and then eat insects or seeds during nonmigratory periods. Previous work suggests that most wild fruits may have plenty of carbohydrates or fats but inadequate protein for birds. Assessing the nutritional adequacy of fruit requires knowing the protein requirements of wild birds during migration in relation to the composition of available fruits. We conducted total collection trials and estimated protein requirements of two species of songbirds, the more frugivorous hermit thrush (Catharus guttatus) and the less frugivorous white-throated sparrow (Zonotrichia albicollis), during nonmigratory and migratory stages of the annual cycle. During both stages, hermit thrush and sparrows lost body mass and had more negative nitrogen balance as dietary protein decreased; hermit thrush but not sparrows ate less as dietary protein decreased even though the diets were isocaloric. Protein requirements of hermit thrush and sparrows in migratory-state (4.3 mg/day, 15.8 mg/day respectively) were significantly lower than when these birds were in nonmigratory-state (53.1 mg/day, 46.0 mg/day respectively). These findings may partially explain why birds during migration can adequately refuel on low-protein foods such as fruits.