Authors: Frank A. La Sorte, Kyle G. Horton, Alison Johnston, Daniel Fink, and Tom Auer
Year: 2022
Publication: Ecosphere
Publication Link: https://doi.org/10.1002/ecs2.3994
Keywords: community science, eBird, light pollution, nocturnal migration, seasonal bird migration, Western Hemisphere
Abstract: Artificial light at night (ALAN) is adversely affecting natural systems
worldwide, including the disorienting influence of ALAN on nocturnally
migrating birds. Understanding how ALAN trends are developing across species’
seasonal distributions will inform mitigation efforts, such as Lights Out
programs. Here, we intersect ALAN annual trend estimates (1992–2013) with
weekly estimates of relative abundance for 42 nocturnally migrating passerine
bird species that breed in North America using observations from the eBird
community science database for the combined period 2005–2020. We use a
cluster analysis to identify species with similar weekly associations with ALAN
trends. Our results identified three prominent clusters. Two contained species
that occurred in northeastern and western North America during the breeding
season. These species were associated with moderate ALAN levels and weak
negative ALAN trends during the breeding season, and low ALAN levels and
strong positive ALAN trends during the nonbreeding season. The difference
between the breeding and nonbreeding seasons was lower for species that
occurred in northern South America and greater for species that occurred in
Central America during the nonbreeding season. For species that occurred in
South America during the nonbreeding season, positive ALAN trends
increased in strength as species migrated through Central America, especially
in the spring. The third cluster contained species whose associations with positive
ALAN trends remained high across the annual cycle, peaking during
migration, especially in the spring. These species occurred in southeastern
North America during the breeding season where they were associated with
high ALAN levels, and in northern South America during the nonbreeding
season where they were associated with low ALAN levels. Our findings suggest
reversing ALAN trends in Central America during migration, especially in the
spring, would benefit the most individuals of the greatest number of species.
Reversing ALAN trends in southeastern North America during the breeding
season and Central America during the nonbreeding season would generate
the greatest benefits outside of migration.