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.

Migratory connectivity and timing for an at-risk Canadian landbird, Eastern Whip-poor-will (Antrostomus vociferus), from two geographically distant breeding areas

“…Physical characteristics of the human-altered landscape and airspace (e.g., urban expan-sion, habitat loss, and pollutants) are considered threats to migrating birds (Kirby et al 2008;Faaborg et al 2010b), yet direct links between environmental conditions in nonbreeding areas and declines in aerial insectivore populations, including Whip-poor-wills, are still poorly documented (Spiller and Dettmers 2019). The full impacts of these anthropogenic effects on migration rates and access to resources such as suitable stopover sites are under investigation (Korpach et al 2022).…”

Migration and the excess exposure of birds to human density in North America

“…2013; Van Doren et al . 2017; Korpach et al . 2022), there is a crucial need for future research that maps out habitat and resource requirements for many bird species throughout the annual cycle, particularly during migration.…”

“…2022b, a). For many of these species, dark-connected skies along their migration routes may be an important resource for successful navigation (Korpach et al . 2022).…”

“…2013), artificial light fragments the aerial landscape and impairs navigation (Van Doren et al . 2017; Korpach et al . 2022), and loss of stopover areas can limit access to resources necessary to fuel migration flight.…”

“…These challenges may have important impacts on the ability of migrants to successfully reach their breeding grounds. For example, window collisions and domestic cats are two major sources of mortality for migrating birds (Loss et al 2013(Loss et al , 2014Machtans et al 2013), artificial light fragments the aerial landscape and impairs navigation (Van Doren et al 2017;Korpach et al 2022), and loss of stopover areas can limit access to resources necessary to fuel migration flight.…”