Archives For osprey nesting platform

Several decades ago, an osprey would be a rare—if not impossible—sight in Cook County in the summer. But now, thanks to the ban on certain pesticides (including DDT), and the creation of osprey nesting platforms, the fish-eating bird is breeding again in local forest preserves.

The osprey looks somewhat like an adult bald eagle, but doesn’t have the eagle’s full white head or tail. Instead, it has a broad brown band through the eye, a brown back, and white belly. An osprey flies with a crook in its wings. Immature bald eagles, with their mottled black and white plumage, can easily be mistaken for ospreys. In summer, visitors can watch an osprey (Pandion haliaetus)—with its 6-foot wingspan—soar above a lake, then plunge in to snatch a meal with its talons to bring to its young. 

PHOTO: Osprey in flight.

Osprey in flight
Photo © Carol Freeman

Once endangered in Illinois, the osprey disappeared as a breeding bird from Illinois about 60 years ago. Scientists think, as with the bald eagle, that when the osprey ingested certain pesticides, the chemicals caused its eggs to thin and crumble during brooding. After DDT was banned, state biologists hoped the osprey would return to breed in Illinois. But the bird needed some help, including cleaning up local waterways and providing nesting areas.

In the 1990s, Cook County Forest Preserves officials, following the lead of biologists in other states, began erecting osprey nesting platforms—40-inch-wide platforms atop 50-foot-tall posts—in the preserves, hoping the ospreys would use them to nest.

It worked. The tall structures gave the ospreys a 360-degree view of their surroundings, something scientists say the birds need when choosing a nesting spot. Today, at least a dozen osprey pairs breed in Cook County, with several more in other nearby counties.

This year, the Chicago Botanic Garden installed an osprey nesting platform, and is waiting to see if a pair will find it to their liking.

According to officials of the Cook County Forest Preserves, 12 osprey pairs bred on man-made platforms in the county in 2014, including at Long John Slough at the Little Red Schoolhouse in Willow Springs. A pair of osprey tending to their nest atop a platform was photographed at Saganashkee Slough in the Palos Preserves this year by Wes Serafin, a long-time proponent of helping ospreys return as a breeding species to Cook County.

PHOTO: An osprey keeps a tight grip on lunch.

An osprey keeps a tight grip on lunch.
Photo © Carol Freeman

The ospreys return in April, often to the same platform they used the previous year. They build a nest of sticks atop the platform, adding new ones each year. The female lays three to four eggs, which hatch in about 38 days. While she broods, the male fiercely defends their territory and brings food to his mate. The young remain in the nest for about two months, begging constantly for food. Then they take their first flights off the platform.

Watching an osprey grab a meal can be fascinating. The bird appears as if it is going to plunge head-first into the water, but then it straightens its head and grasps the fish with its talons. Two forward-facing and two backward-facing toes have sharp spines that enable the bird to clutch the fish. Occasionally an osprey will grab a fish too heavy for it to carry, in which case the osprey might drop it, and try for another meal.

The osprey that nest in northern Illinois in summer spend winters in Florida, Mexico, and South America.

The Illinois Department of Natural Resources is now in the fourth year of their program designed to bring more osprey to the state to increase the number of breeding pairs.

The osprey is the July bird species highlighted by the Forest Preserves of Cook County. Come #birdthepreserves with the FPDCC; view the list of upcoming events for free events near you.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

Look up! In partnership with Friends of the Chicago River (FOCR) and the Forest Preserves of Cook County (FPCC), an osprey nesting platform was installed on Friday, January 29, along the North Branch Trail at the south end of the Chicago Botanic Garden near Dundee Road.

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The Garden’s new osprey nesting platform is located near Dundee Road and is viewable from the North Branch Trail.

The osprey is listed as an endangered species in Illinois, which means it’s at risk of disappearing as a breeding species. Fish-eating raptors that migrate south and winter from the southern United States to South America, osprey are often seen during their migrations—yet few remain in Illinois to nest. The lack of suitable nesting structures has been identified as a limiting factor to their breeding success here.

Males attract their mates to their strategically chosen nesting location in the spring. In order for a nest to be successful, it must be located near water (their diet consists exclusively of fish, with largemouth bass and perch among their favorites), the nest must be higher than any other nearby structure, and it must be resistant to predators (think raccoons) climbing the nest pole and attacking the young.

FOCR and the FPCC sought out the Garden as a partner for an installation site, in large part owing to the Garden’s strong conservation messaging and proximity to other nearby nesting platforms that have been recently installed (two are located alongside the FPCC’s Skokie Lagoons just to the south).

The Garden’s nesting platform was installed atop an 80-foot “telephone pole,” set 10 feet into the ground and extending upwards by 70 feet. The 40-inch hexagonal nest platform atop the pole has a wire mesh on the bottom so that water can pass through the sticks and stems that the osprey will bring to construct the nest.

PHOTO: Installing and osprey nesting pole.

A truck-mounted auger and crane set the nesting pole and platform into place.

PHOTO: Installing an osprey nesting pole.

The nesting platform sits atop the pole and is ideally sized for a future osprey nest; notice that we even “staged” the new osprey home with a few sticks of our own!

PHOTO: Installing an osprey nesting pole.

A metal band was wrapped near the bottom of the pole to prevent predators from being able to climb it.

PHOTO: Installing an osprey nesting pole.

The nesting pole and platform is fully installed and is visible from the North Branch Trail that runs through the Garden.

With the osprey nesting platform now in place, our hope is that within the next few years, a migrating male will select the site and pair with a female. Osprey generally mate for life, though they’re together only during the breeding and rearing seasons.

You can learn more about the how and why of the osprey nesting platform project at the FOCR website. Follow the links on that webpage for images, video, and a press release relating to the installation of an identical osprey platform at the Skokie Lagoons last spring.

Read more about the long-term effort, and about ospreys making a comeback in Cook County. Discover birding at the Garden and find our full bird list online at chicagobotanic.org/birds.


©2016 Chicago Botanic Garden and my.chicagobotanic.org