Evidence of widespread movements from breeding to molting grounds by North American landbirds

ABSTRACT Precise locations for the complete feather molt of North American landbirds, relative to their breeding territories, remain undocumented for most species. We analyzed >760,000 records of 140 species at 936 bird-capture stations to assess probabilities of recording both molting landbirds at their breeding sites and breeding birds at molting sites, and to investigate latitudinal, longitudinal, and elevational shifts from breeding to molting grounds. We demonstrate widespread evidence for molt-migrations among a variety of North American landbirds, including many migratory species previously thought to molt on “breeding grounds.” Geospatial differences between breeding and molting grounds were detected in all 4 compass directions as well as both upslope and downslope in elevation, while individuals of some species appeared to disperse to specific molting locations not discriminated by spatial direction or elevation from breeding territories. Although western North American species and populations ar...