The “Western” Flycatcher Problem

In 1989, the American Ornithologists’ Union split the Western Flycatcher into two species: Pacific-slope Flycatcher and Cordilleran Flycatcher. The conventional wisdom is that they are impossible to identify by plumage or structure, even in the hand. Voice is the only field mark. However, the situation with their vocalizations is quite messy, and worthy of an in-depth examination. [Read more]