A Comparison of Foraging Behavior among Permanent, Summer, and Winter Resident Bird Groups

Abstract

Foraging behavior of permanent resident bird species in summer and winter was compared with that of summer resident and winter resident bird groups of a floodplain habitat along the lower Snake River in southeastern Washington [USA]. Ten criteria were used to compare foraging differences between seasonal groups. In summer, permanent residents differed significantly from invading summer residents in 8 of 10 foraging categories. In summer, permanent residents foraged on the forest edge, in the tree-shrub physiognomic type and usually on the ground. Summer residents differed by feeding more frequently in trees or in the air and by gleaning insects off mulberry or willow leaves. In winter, permanent residents foraged on the ground of the forest edge, either in the tree-shrub or grass-herb physiognomic types. Winter residents fed in trees or on the ground, in the woods or forest edge and in the tree-shrub physiognomic type. When in trees, these birds usually gleaned insects off small branches and dead leaves. Separation of foraging behavior was .apprx. 6 times greater in winter than in summer.