Wildlife biologist Chuck Rizzo climbs into what looks like an enormous white bucket and slowly begins to rise.
The metal arm of an aerial lift truck propels him higher and higher, above thick underbrush and then even some treetops, toward a striking sight in an otherwise ordinary Cook County, Illinois, forest preserve: a sturdy, stick-strewn platform built on top of a 50-foot telephone pole.
“How is it?” the lift operator yells as he maneuvers the bucket carrying the wildlife biologist. “Want it over?”
“Yeah, get it closer,” Rizzo says.
Then he reaches toward the sticks and lifts out two pudgy osprey chicks with bulging chocolate-brown eyes and bellies covered in fluff.
The chicks, which will be examined by a vet and returned to their high-rise home, are a sign of success for a Forest Preserves of Cook County program that aims to increase the number of once-endangered ospreys in the Chicago area by constructing towering nesting platforms.
The Forest Preserves program now bands up to 30 chicks a year, all raised by wild osprey—also known as sea hawks—that choose to build their massive nests on human-built platforms standing 50 to 80 feet above the ground.
That’s up from a handful of chicks in the first year of banding in the 1990s, according to Forest Preserves wildlife biologist Chris Anchor, who started the osprey nesting program after spotting nesting platforms in northern Wisconsin.
“What we’ve done is we’ve greatly increased the speed at which ospreys have populated Cook County,” Anchor said.
Studies of similar programs have found that the platforms attract ospreys and produce successful nests, and the platforms are widely used in many areas of the United States.
Still a threatened species in Illinois, ospreys—fish-eating raptors with 5-foot wing spans—were once endangered in the state, due to the widespread use of the pesticide DDT, which weakened the shells of their eggs.
But with a ban on DDT in 1972, the white-bellied birds with dark wings and facial markings are on the rise in Illinois.
“They’ve increased dramatically and they’ve also spread,” said Field Museum senior conservation ecologist Doug Stotz. “They’re most common in the northern part of the state, but there are multiple osprey nests downstate.”
The Illinois Natural History Survey’s 2023 spring bird count reported a record number of osprey sightings (181) in a record number of counties (43). In 2022, the bird count reported 22 osprey sightings in Cook County in the course of one day.
The Chicago area may seem like an odd place for ospreys, but the imposing birds—about 1½ times the size of a red-tailed hawk—are relatively tolerant of people if they have a good nest site, Stotz said.
He also noted the presence of the nesting platforms, and the abundance of lakes in the county, both natural and artificial.
“Almost every (Cook County) forest preserve has a lake, and that’s the main thing they’re looking for,” he said.
Anchor used to climb the telephone poles that support the nesting platforms and retrieve the chicks himself, with just a harness and spiked shoes.
But on a recent visit to Lake Avenue Woods forest preserve near Mount Prospect, he was accompanied by Rizzo, the wildlife biologist, as well as a veterinarian, a wildlife technician, two representatives from a county that’s starting its own osprey platform breeding program, and eight other observers and helpers.
Anchor, who is a few years from retirement, wants to give his staff hands-on experience, so today it would be Rizzo who would retrieve the osprey chicks.
After an early morning visit to a nesting platform that rose above a restored prairie, the group, minus Anchor, headed 35 miles south to Sag Quarries nature preserve near Lemont.
It was a good site for osprey, with dense forest and wide lakes formed from old limestone quarries, but humans driving on unpaved paths had to watch out for low branches, steep inclines and deep, skid-inducing ruts.
By the time the nest appeared in sight, the sun was blazing and the team set up an umbrella above a makeshift examining table formed by the back panel of a forest preserve pickup truck.
The big bucket truck that lifted Rizzo into a cloudless blue sky rumbled loudly, and the parents of the chicks circled above, screaming “Pew! Pew! Pew! Pew!”
When Rizzo finally ascended to the nest platform, he found two chicks that were about three or four weeks old, and in the sweet spot for examination and banding.
“If they’re bigger sometimes they’ll try to go to the other side (of the nest),” Rizzo said when he came down. But these chicks were “definitely chill,” and stayed put, making his job easier.
The chicks were already large—about a foot long—with stern stares, handsome head feathers and well-formed black beaks. But below the neck, they were still awkward and unformed, with stubby feathers and soft baby fluff.
Once a member of the team held a chick’s legs—disabling its already formidable black talons—the bird would sit quietly in his or her arms.
On the ground, forest preserves wildlife field technician Melina Frezados weighed and measured the birds and gently affixed lightweight aluminum bands with unique numbers to their right legs, using a wrench and pliers.
John Winter, a veterinarian and the zoological and wildlife health management resident at Brookfield Zoo Chicago, gave each bird a thorough exam, including their eyes, ears and feet. He also took mouth swabs and blood samples.
The chicks protested occasionally, letting out an indignant “Chuh! Chuh!” but they mostly lay back on the examining table, their pale fuzz-covered chests rising and falling.
Their parents were less accepting. One sat in a dead tree, glaring down at the proceedings, while the other returned repeatedly to scream at the interlopers.
The team left quickly once Rizzo had placed the chicks back in their nest, so the parents could return to their young as soon as possible.
Banding allows the birds to enter the 7 million-band database at the U.S. Geological Survey Bird Banding Laboratory in Laurel, Maryland.
Banding tracks where birds eat, nest and migrate, and allows researchers to see population trends over time, according to Suzy Peurach, a biologist at the Bird Banding Laboratory.
Ospreys migrate as far as Central and South America, and Peurach said that a Cook County osprey was recently spotted in Colombia—more than 2,000 miles from Chicago.
Reports are made using the identifying numbers on the birds’ leg bands.
One of the secrets of the osprey program’s success, Anchor said, is to put nests where ospreys are already spending time, not where you want them to be.
“Every pair of osprey has their own behavior patterns: Some are very tolerant of people and some are completely ill-tolerant,” he said.
“We have pairs of ospreys where if you come within a half mile of the nest, they’ll be up in the air screaming for the next 30 minutes or an hour. So they’re not taking care of their babies. We’ve got other pairs that are in fishing areas, near lakes, and people are fishing literally, right underneath the nest, and the ospreys could care less,” he said.
When the birds fledge, they fly south, where the females will stay for two years, becoming sexually mature, before they return to the area where they were born, with their mates in tow, he said.
Ospreys generally mate for life, and birds will often return year after year to the same nest site.
This year the Forest Preserves program lost at least four nests to storms, but they still have 13 nests on 21 platforms, and about 25 to 30 chicks, Anchor said.
“The fact that we have an apex predator now living among us, in the third-largest metropolitan area in North America—that’s significant,” he said. “That’s a real testament that things are headed in the right direction.”
This article by Nara Schoenberg, Chicago Tribune was first published by Phys.org on 11 July 2024. Lead Image: Credit: CC0 Public Domain.
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