Science & Nature
Cook County Osprey’s Unexpected 2,500-Mile Odyssey Has a Happy Ending
A juvenile osprey given a metal ID band as part of Cook County’s program. (Courtesy Forest Preserve District of Cook County)
For more than 30 years, Cook County wildlife biologist Chris Anchor and his colleagues have been attaching metal ID bands to the legs of various birds — thousands in all — and every great once in a while, one of those birds, or maybe just its tag, is found.
They mostly turn up in expected places — the Gulf Coast and areas along the Mississippi River — but this past summer, Anchor received a report from the federal bird banding lab in Maryland that one of Cook County’s ospreys had landed in Colombia.
“I was thinking Columbia, Missouri,” said Anchor, who’s spent his career at the Forest Preserve District of Cook County studying the region’s wildlife.
“I would have never guessed that the animals were going to Colombia, the country. If you had asked me, I would have said that they’d gone to Florida, Georgia, Alabama, Louisiana. But it never occurred to me that they’re going to Central and South America,” said Anchor, who nearly ran out of adjectives to describe the osprey’s amazing odyssey.
“This is incredible. We’ve had nothing nearly as remarkable as this,” he said. “This is extraordinary. After 30 years of banding, this is the most exceptional return that we’ve ever had.”
To gild the tale even further, the bird, which hatched in 2023, was sighted in Colombia almost a year to the day of when it was banded at Sag Quarries in suburban Lemont.
When it was discovered this past June, lying on a sidewalk in Bucaramanga — a medium-sized Colombian city of 600,000, known for its parks — the osprey wasn’t only 2,500 miles from home, it was dehydrated and stressed.
“Somebody picked it up, they gave it water and it flew away. So it’s still alive,” Anchor said. “But it’s truly, truly remarkable that the bird went that far.... Lord knows what it ran into flying over the gulf.”
Ospreys, though, are used to defying the odds.
Man-made platforms give ospreys a place to nest safe from predators like raccoons. (jimodenney / iStock)
Also known as sea hawks, ospreys were among the species of birds whose numbers steeply declined between the 1950s and ‘70s due to the pesticide DDT, which had the effect of thinning the birds’ eggshells. Bald eagles nearly went extinct for the same reason.
Once DDT was banned, the osprey population began to recover, only to encounter new challenges either directly or indirectly caused by humans.
Their breeding habitat — from nesting sites to hunting grounds — has either been encroached on or completely overrun by development. And as people moved into an area, other critters followed, lured by the prospect of free and easy meals in the form of food waste.
“Cook County, in general, has the highest densities of raccoons than you’ll find anywhere else in the state,” Anchor said. “They are very adaptable, and they have learned to live amongst us and exploit our excesses. Raccoons don’t have to earn a living around us. They can go from trash can to trash can and they’re doing great.”
What’s great for raccoons is not so great for ospreys.
Birds in Cook County, including ospreys, are “under incredible pressure ... because of raccoon predation,” Anchor explained, which isn’t to demonize raccoons, he was quick to add — they’re just trying to get by like everyone else.
The solution was for humans to give the ospreys a leg up, literally.
Cook County set up its first nesting pole for ospreys in the Palos region in the early ‘90s, after Anchor spied similar platforms while visiting northern Wisconsin.
The ospreys took to the man-made structure immediately and in the decades since, the forest preserve has erected roughly 25 poles throughout the county. Today, Cook County has the largest urban osprey platform project in the U.S., according to Anchor.
The program has yielded some interesting insights into osprey behavior.
The birds feed almost exclusively on fish, typically caught within 5 to 10 miles of their nest. They have a habit of bringing their prey back to the nest, eating their fill and then tossing the fish heads off the platform onto the ground below. Picking through the discarded bits — no one said being a wildlife biologist was glamorous — Anchor expected to come across carp and shad, but in some instances, he ID’d lake salmon and trout.
This, from a nest platform in Palos Hills.
“Think of where Palos Hills is, then think of where Lake Michigan is. Now think of all the waterways between Palos and Lake Michigan. Why would they travel that far?” Anchor asked. “The only thing that we can think of is that salmon and trout have a very high fat content. So it’s worth the energy that they give up traveling to and fro to bring back that type of food.”
A map of where birds banded in Cook County, or just their tags, have been found. (Courtesy Forest Preserve District of Cook County)
Each breeding season, forest preserve staff, along with veterinarians from partner agencies, visit the osprey nests to band the new hatchlings. The biologists have a short two-week window where the babies are big enough to put a band on them but not too big to fly or fall out of the nest. If the weather doesn’t cooperate during that brief timeframe — too hot, too rainy or too windy — biologists won’t risk disturbing the birds.
“So some years, we’ll band 20, 25 babies; some years we’ll band three or four,” Anchor said.
Ospreys are just one species the forest preserves bands, not all of them endangered or threatened — red-winged blackbirds and sparrows, among others, are included in the survey. It’s part of a cooperative effort between the U.S. and Canada that’s been ongoing for nearly 100 years.
“It’s to understand movements of birds, it’s to understand population trends, it’s to understand general demographics, what habitats they’re using, what habitats they’re not using,” Anchor explained.
Biologists also conduct health assessments on the birds as part of the banding process, gathering information on potential diseases like avian influenza.
The birds, and wildlife in general, are used as bio-indicators of the health of the environment, as well. Because of their fish diet, osprey, for example, are an indicator of the health of our waterways — if a river or lake can’t support fish, osprey won’t be present. At the same time, if fish are absorbing toxins from the water, those chemicals would show up in ospreys’ blood samples taken during health assessments.
This type of information is of value to public health, Anchor said, because it gives us an idea of what’s happening in the environment that we all share, animals and humans alike.
‘Pure Serendipity’
Cook County’s well-traveled osprey, on the day it was banded in 2023. Held by Melina Frezados, wildlife biologist with Cook County forest preserves. (Courtesy of Forest Preserve District of Cook County)
Of the billions of birds on the planet, a lone osprey with a unique ID band was found in Colombia and linked to Cook County. The likelihood of that occurrence is so slim as to warrant all the superlatives.
But it also highlights birds’ reliance on human compassion and generosity — particularly migratory birds like ospreys — at all points along their journeys, from their breeding grounds to their wintering sites and all points in between.
Cook County has done its part, Anchor said, by setting aside nearly 70,000 acres of forest preserve land and supporting the wildlife that call those preserves home or are just passing through.
He’s grateful that a continent away, an osprey from Chicago met with the same consideration.
“How remarkable it is and fortuitous, pure serendipity, that it should end up someplace where someone was willing to lend a hand and help it through its low point there and send it on its way,” Anchor said.
Contact Patty Wetli: @pattywetli | (773) 509-5623 | [email protected]
