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Title: The role of artificial light at night and road density in predicting the seasonal occurrence of nocturnally migrating birds
Abstract Aim

Artificial light at night (ALAN) and roads are known threats to nocturnally migrating birds. How associations with ALAN and roads are defined in combination for these species at the population level across the full annual cycle has not been explored.

Location

Western Hemisphere.

Methods

We estimated range‐wide exposure, predictor importance and the prevalence of positive associations with ALAN and roads at a weekly temporal resolution for 166 nocturnally migrating bird species in three orders: Passeriformes (n = 104), Anseriformes (n = 27) and Charadriiformes (n = 35). We clustered Passeriformes based on the prevalence of positive associations.

Results

Positive associations with ALAN and roads were more prevalent for Passeriformes during migration when exposure and importance were highest. Positive associations with ALAN and roads were more prevalent for Anseriformes and Charadriiformes during the breeding season when exposure was lowest. Importance was uniform for Anseriformes and highest during migration for Charadriiformes. Our cluster analysis identified three groups of Passeriformes, each having similar associations with ALAN and roads. The first occurred in eastern North America during migration where exposure, prevalence, and importance were highest. The second wintered in Mexico and Central America where exposure, prevalence and importance were highest. The third occurred throughout North America where prevalence was low, and exposure and importance were uniform. The first and second were comprised of dense habitat specialists and long‐distance migrants. The third was comprised of open habitat specialists and short distance migrants.

Main conclusions

Our findings suggest ALAN and roads pose the greatest risk during migration for Passeriformes and during the breeding season for Anseriformes and Charadriiformes. Our results emphasise the close relationship between ALAN and roads, the diversity of associations dictated by taxonomy, exposure, migration strategy and habitat and the need for more informed and comprehensive mitigation strategies where ALAN and roads are treated as interconnected threats.

 
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Award ID(s):
1927743 1939187
NSF-PAR ID:
10446842
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
Diversity and Distributions
Volume:
28
Issue:
5
ISSN:
1366-9516
Page Range / eLocation ID:
p. 992-1009
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Abstract Aim

    Two important environmental hazards for nocturnally migrating birds are artificial light at night (ALAN) and air pollution, with ambient fine particulate matter (PM2.5) considered to be especially harmful. Nocturnally migrating birds are attracted to ALAN during seasonal migration, which could increase exposure to PM2.5. Here, we examine PM2.5concentrations and PM2.5trends and the spatial correlation between ALAN and PM2.5within the geographical ranges of the world’s nocturnally migrating birds.

    Location

    Global.

    Time period

    1998–2018.

    Major taxa studied

    Nocturnally migrating birds.

    Methods

    We intersected a global database of annual mean PM2.5concentrations over a 21‐year period (1998–2018) with the geographical ranges (breeding, non‐breeding and regions of passage) of 225 nocturnally migrating bird species in three migration flyways (Americas,n = 143; Africa–Europe,n = 36; and East Asia–Australia,n = 46). For each species, we estimated PM2.5concentrations and trends and measured the correlation between ALAN and PM2.5, which we summarized by season and flyway.

    Results

    Correlations between ALAN and PM2.5were significantly positive across all seasons and flyways. The East Asia–Australia flyway had the strongest ALAN–PM2.5correlations within regions of passage, the highest PM2.5concentrations across all three seasons and the strongest positive PM2.5trends on the non‐breeding grounds and within regions of passage. The Americas flyway had the strongest negative air pollution trends on the non‐breeding grounds and within regions of passage. The breeding grounds had similarly negative air pollution trends within the three flyways.

    Main conclusions

    The combined threats of ALAN and air pollution are greatest and likely to be increasing within the East Asia–Australia flyway and lowest and likely to be decreasing within the Americas and Africa–Europe flyways. Reversing PM2.5trends in the East Asia–Australia flyway and maintaining negative PM2.5trends in the Americas and Africa–Europe flyways while reducing ALAN levels would likely be beneficial for the nocturnally migrating bird populations in each region.

     
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  2. Abstract Aim

    A unique risk faced by nocturnally migrating birds is the disorienting influence of artificial light at night (ALAN). ALAN originates from anthropogenic activities that can generate other forms of environmental pollution, including the emission of fine particulate matter (PM2.5). PM2.5concentrations can display strong seasonal variation whose origin can be natural or anthropogenic. How this variation affects seasonal associations with ALAN and PM2.5for nocturnally migrating bird populations has not been explored.

    Location

    Western Hemisphere.

    Time Period

    2021

    Major Taxa Studied

    Nocturnally migrating passerine (NMP) bird species.

    Methods

    We combined monthly estimates of PM2.5and ALAN with weekly estimates of relative abundance for 164 NMP species derived using observations from eBird. We identified groups of species with similar associations with monthly PM2.5. We summarized their shared environmental, geographical, and ecological attributes.

    Results

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    Main Conclusions

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  3. Abstract

    The spatial extent and intensity of artificial light at night (ALAN) has increased worldwide through the growth of urban environments. There is evidence that nocturnally migrating birds are attracted toALAN, and there is evidence that nocturnally migrating bird populations are more likely to occur in urban areas during migration, especially in the autumn. Here, we test if urban sources ofALANare responsible, at least in part, for these observed urban associations. We use weekly estimates of diurnal occurrence and relative abundance for 40 nocturnally migrating bird species that breed in forested environments in North America to assess how associations with distance to urban areas andALANare defined across the annual cycle. Migratory bird populations presented stronger than expected associations with shorter distances to urban areas during migration, and stronger than expected association with higher levels ofALANoutside and especially within urban areas during migration. These patterns were more pronounced during autumn migration, especially within urban areas. Outside of the two migration periods, migratory bird populations presented stronger than expected associations with longer distances to urban areas, especially during the nonbreeding season, and weaker than expected associations with the highest levels ofALANoutside and especially within urban areas. These findings suggest thatALANis associated with higher levels of diurnal abundance along the boundaries and within the interior of urban areas during migration, especially in the autumn when juveniles are undertaking their first migration journey. These findings support the conclusion that urban sources ofALANcan broadly effect migratory behavior, emphasizing the need to better understand the implications ofALANfor migratory bird populations.

     
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    Location

    North America.

    Time period

    Full annual cycle, 2011–2016.

    Major taxa studied

    Nocturnally migrating landbirds.

    Methods

    We used observations of nocturnally migrating landbirds from the eBird community‐science programme to estimate weekly spatial distributions of total biomass, abundance and species richness. We related these patterns to primary productivity and seasonal productivity surplus estimated using a remotely sensed measure of vegetation greenness.

    Results

    All three avian metrics showed positive spatial associations with primary productivity, and this was more pronounced with seasonal productivity surplus. Surprisingly, biomass showed a weaker association than did abundance and richness, despite being a better indicator of energetic requirements. The strength of associations varied across seasons, being the weakest during migration. During spring migration, avian biomass increased ahead of vegetation green‐up in temperate regions, a pattern also previously described for herbivorous waterfowl. In the south‐eastern USA, spring green‐up was instead associated with a net decrease in biomass, and winter biomass greatly exceeded that of summer, highlighting the region as a winter refuge for short‐distance migrants.

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    Location

    The Americas.

    Taxon

    Grey‐cheeked Thrush (Catharus minimus, Aves, Passeriformes, Turdidae), Birds.

    Methods

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    Results

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