Data from: Environmental and geographic conditions on the breeding grounds drive Bergmannian clines in nightjars

Abstract

We assembled a cross-continental dataset from 29 researchers to assess: Whether three species of migratory nightjars (Family Caprimulgidae) adhere to Bergmann's rule; Whether environmental factors on the breeding or wintering grounds determine body size; and Which mechanistic hypotheses best explain Bergmannian patterns in body size. We captured 7,318 Caprimulgids (3,388 used in final analysis) using mist nets and conspecific playback across North America and Europe, a subset of 215 of which were equipped with telemetry tags to obtain winter locations.