Urbanization and artificial light at night reduce the functional connectivity of migratory aerial habitat

Abstract

Flying animals use aerial habitats to forage, communicate and travel. However, human activities that fragment aerial habitat with built structures, noise, and chemical or light pollution, may limit the ability of wildlife to use airspace efficiently. Applying landscape connectivity theory to aerial habitats could reveal how long‐distance migrants respond to sources of aerial habitat fragmentation along their migratory routes. Artificial light at night is a major component of urbanization that fragments dark skies across North America. Attraction of nocturnal migrants to urban light is well documented, but species‐specific responses, especially throughout a full migration from breeding to wintering grounds, are not. We tested hypotheses about long‐distance migratory movements in relation to artificial light using a highly nocturnal, Nearctic‐Neotropical avian migrant (Eastern whip‐poor‐will Antrostomus vociferus). We applied a resource selection framework at multiple spatial scales to explore whether GPS‐tracked birds (n = 10) responded to urbanization in general, or artificial light specifically, during migratory flights. We found little evidence of attraction to artificial light during nocturnal flights. Artificial light and urbanization were highly correlated and difficult to disentangle, but the birds generally avoided urban areas and selected dark‐connected skies for travel. Migratory stopovers (locations where GPS‐tracked birds (n = 20) paused for at least one night), were located almost exclusively in dark, rural areas. Our results illustrate that considering how nocturnal aerial migrants respond to both aerial and terrestrial habitat elements can improve our understanding of what may facilitate their long‐distance movements.