Relationship of Nutritional Condition of Permanent-Resident Woodland Birds With Woodlot Area, Supplemental Food, and Snow Cover

In a previous study we found that survivorship of several species of permanent-resident, temperate-zone birds was positively related to forest fragment size and presence of supplemental food, and negatively related to extent of snow cover (Doherty and Grubb 2002). Here, we test the hypothesis that such trends are related to differential nutritional condition during winter. Employing rate of growth of induced feathers, we found that woodlot size and presence of supplemental food interacted to increase the nutritional condition of Carolina Chickadees (Poecile carolinensis) and that Tufted Titmouse (Baeolophus bicolor) nutritional condition was reduced in years with high snow cover. Assuming that nutritional condition is positively related to survivorship, these results have possible implications for the viability of permanent-resident birds in small woodlots, with the effects on subordinate species in foraging flocks in very small woodlots possibly being the most severe.