Once a year, scientists and veterinarians visit Baker’s Lake in northwest Cook County to draw blood from and track the movements of great egrets – a type of heron that builds nests in trees.
The birds are on a small island with a rookery, or breeding colony of nests.
The group is led by Chris Anchor, senior wildlife biologist at the Forest Preserve District of Cook County, and Dr. Tom Meehan, vice president of veterinary services at the Chicago Zoological Society.
The plan is to collect blood from young birds in order to see what they’re exposed to through their diet of mostly fish.
“We’re looking for heavy metals and pesticides in the blood,” Anchor said. “We’re looking to use them as biomonitors to understand the health of the environment they’re living in – and ultimately, we’re living in.”
Meehan and his team perform the blood chemistry tests, which can sometimes provide information regarding human health concerns.
“One of the things in the not-too-distant past we were worried about – avian influenza – that’s a virus that can be carried by birds and affect people,” Meehan said. “Avian influenza is one of those things that we can monitor these birds for.”
While great egrets are native to Illinois, they migrate south once the temperature drops.
To track the birds, metal bands with distinctive numbers are secured to their legs. Wildlife professionals are able to track them across the country by submitting that data to the U.S. Geological Survey.
“We’ve had birds that have been recovered down in Florida, Georgia,” Anchor said. “We had one caught in Cape Canaveral a couple years ago, which was very interesting.”
The great egrets at Baker’s Lake are just one of the species the Cook County forest preserve monitors. They keep track of everything from area coyotes to turtles to bats.
Follow Evan Garcia on Twitter: @EvanRGarcia
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