CHAMPAIGN, Ill., 9/17/19: Wading into the springtime muddy marshland, pushing aside a wall of plants taller than her head, ornithologist Anastasia Rahlin looks and listens for signs of black terns and yellow-crowned night herons. She plays a recording, waits 30 seconds, and listens for a return call.
The species of birds that she doesn’t find in the marsh are the ones she doesn’t want scientists to forget.
As urbanization increases in parts of Illinois, one-third of bird species are declining, especially in the Great Lakes areas. Rahlin, of the Illinois Natural History Survey, Stephanie Beilke with Audubon Great Lakes, and Sarah Saunders of the National Audubon Society studied how various birds living in wetland patches respond to their city surroundings.
“There’s a reason why very few data are available on birds in marshland habitats,” Rahlin said. “Some of the species are secretive and sneaky, such as king rails, and they are well camouflaged in the tall vegetation.”
Using three years of data from surveys of sites in Illinois and Indiana, the scientists focused on 17 bird species. They did not find any black terns and and yellow-crowned night herons. Species that also tend to drop in number with increasing urbanization include American coots, pied-billed grebes, soras, and Virginia rails.
The surveys also revealed larger populations of the species that thrive, even when the urban wetland is only a small patch, such as swamp sparrows, marsh wrens, and least bitterns.
Her concern about the survey findings, said Rahlin, is that when only a few individual birds are found, there is not enough information to include the species in occupancy and abundance models that determine how wetland birds respond to different habitats, including those close to a bustling city.
“Some bird species are silently dropped from research studies because there are too few birds from which to get enough data,” Rahlin said. “It’s important to include them in models to better understand their habitat requirements. We need species-specific studies or they will disappear.”
In this study, Rahlin said she did not find enough yellow-headed blackbirds, king rails, American bitterns, and little blue herons to include in habitat models.
From survey findings and the collaboration with Audubon, the good news is that previous marshland restoration efforts have been highly successful, particularly in the heavily polluted Calumet area on the bottom edge of Lake Michigan.
“Even just a little bit of marsh restoration can bring back species that have been lost to urbanization,” Rahlin said.
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