Not Singing in the Rain: Linking Migratory Songbird Declines With Increasing Precipitation and Brood Parasitism Vulnerability
Kristen M. Rosamond1,
Sandra Goded1,
Alaaeldin Soultan2,
Rachel H. Kaplan1,3,
Alex Glass3,4,
Daniel H. Kim3,5 and
Nico Arcilla1,3,6*
- 1International Bird Conservation Partnership, Monterey, CA, United States
- 2Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden
- 3Crane Trust, Wood River, NE, United States
- 4Cooperative Wildlife Research Laboratory, Southern Illinois University, Carbondale, IL, United States
- 5U.S. Fish and Wildlife Service, Pierre, SD, United States
- 6Center for Great Plains Studies, University of Nebraska–Lincoln, Lincoln, NE, United States
ABSTRACT
Few empirical studies have quantified relationships between changing
weather and migratory songbirds, but such studies are vital in a time of
rapid climate change. Climate change has critical consequences for
avian breeding ecology, geographic ranges, and migration phenology.
Changing precipitation and temperature patterns affect habitat, food
resources, and other aspects of birds’ life history strategies. Such
changes may disproportionately affect species confined to rare or
declining ecosystems, such as temperate grasslands, which are among the
most altered and endangered ecosystems globally. We examined the
influence of changing weather on the dickcissel (Spiza americana),
a migratory songbird of conservation concern that is an obligate
grassland specialist. Our study area in the North American Great Plains
features high historic weather variability, where climate change is now
driving higher precipitation and temperatures as well as higher
frequencies of extreme weather events including flooding and droughts.
Dickcissels share their breeding grounds with brown-headed cowbirds (Molothrus ater),
brood parasites that lay their eggs in the nests of other songbirds,
reducing dickcissel productivity. We used 9 years of capture-recapture
data collected over an 18-year period to test the hypothesis that
increasing precipitation on dickcissels’ riparian breeding grounds is
associated with abundance declines and increasing vulnerability to
cowbird parasitism. Dickcissels declined with increasing June
precipitation, whereas cowbirds, by contrast, increased. Dickcissel
productivity appeared to be extremely low, with a 3:1 ratio of breeding
male to female dickcissels likely undermining reproductive success. Our
findings suggest that increasing precipitation predicted by climate
change models in this region may drive future declines of dickcissels
and other songbirds. Drivers of these declines may include habitat and
food resource loss related to flooding and higher frequency
precipitation events as well as increased parasitism pressure by
cowbirds. Positive correlations of June-July precipitation, temperature,
and time since grazing with dickcissel productivity did not mitigate
dickcissels’ declining trend in this ecosystem. These findings highlight
the importance of empirical research on the effects of increasing
precipitation and brood parasitism vulnerability on migratory songbird
conservation to inform adaptive management under climate change.