Feeding Ecology of the Red‐eyed Vireo (Vireo olivaceus) and Associated Foliage‐Gleaning Birds

Abstract

The sexes of the Red—eyed Vireo, an abundant insectivorous bird in eastern deciduous woodlands, differed in their foraging heights, with an overlap of only about 35%. The males foraged higher than the females, and non—random sequences of movements were employed to maintain this separation. The foraging level and the nest height of female Red—eyes was similar, whereas the males foraged closer to their singing perches. Thus the foraging efficiency of both sexes was likely greater in accordance with their differing behavior roles. The "small" territory (1.3—1.7 acres) of this species actually consists of a cylinder extending from the forest canopy to the low understory. The associated White—eyed Vireo (Vireo griseus) was generally separated from Red— eyed Vireo by habitat, and the Yellow—throated Vireo (Vireo flavifrons) overlaps in habitat but possesses structural and behavioral differences which indicate different prey preferences. Foraging behavior of migrating Red—eyed Vireos differs markedly from that of breeding birds. Differences were also noted between summer and winter foraging behavior patterns in the White—eyed Vireo. All three vireo species exhibit species—specific patterns of foraging movements. Two other foliage—gleaning insectivorous birds occupying the same forests, the American Redstart (Setophaga ruticilla) and the Acadian Flycatcher (Empidonax virescens), also possess species—specific foraging behaviors (niche—exploitation patterns).