The status of the Willow and Pacific-slope flycatchers in northwestern California and southern Oregon

Abstract

The Willow (Empidonax traillii) and Pacific-slope (E. dificilis) flycatchers are generally similar in their morphology and foraging, but differ in their habitat and population dynamics. Through a concentration of constant-effort mist-netting stations, we documented the movements and composition of populations over a relatively large geographical province of southern Oregon and northern California. Although the Pacific-slope Flycatcher is far more common as a breeding species in much of the province, it becomes much less common than the Willow Flycatcher during migration. After breeding, the Willow Flycatcher has a previously undocumented major influx of birds into the province from breeding sites to the north, including both young and adults. By contrast, the Pacific-slope Flycatcher appears to migrate differentially, with adults moving south before the young.

Citation

Ralph, C. John; Hollinger, K. 2003. The status of the Willow and Pacific-slope flycatchers in northwestern California and southern Oregon. Studies in Avian Biology 26:104-117