The Osprey Project & Bird Basics
The Osprey Cam Project
In 2012, a bird cam was installed on top of the Observation Tower at Collins Marsh. Today, you can view the live stream year around. Osprey typically occupy the nest during the summer months; and snow owls have been seen here in the winter.
We are so thankful for all of the help we received while completing the Osprey Project. Many thanks to Aaron Buccholz of the DNR for his continued support, to the CEI’s Board Members for doing research, Lincoln High School’s shop department for helping us prepare the camera’s mount, to Tom Ward, Gary Drohman, Tom Bouc, Kyle Korinek and Dana Bongle for bravely climbing the tower with Adam to install it, and of course, the Forward Endowment and Neustadter family for providing us with the much needed funds to make the whole thing possible.
If you would like to see this project continue, or for us to work on more projects like this, please consider becoming a member or making a financial donation to CEI. Our organization could not survive without your donations of time, money, and support.
Bird Basics: The Osprey
Osprey are a unique raptor that can be found in Wisconsin only during the summer months. These graceful birds can be seen soaring in the sky over Collins Marsh and diving into the water with tremendous speed to catch their next meal.
Habitat
Unable to dive to more than about three feet below the water’s surface, Ospreys gravitate toward shallow fishing grounds, frequenting deep water only where fish school near the surface. Ospreys nest in a wide variety of locations, from Alaska to New England, Montana to Mexico, Carolina to California; their habitat includes almost any expanse of shallow, fish-filled water, including rivers, lakes, reservoirs, lagoons, swamps, and marshes. Whatever the location, Osprey nesting habitat must include an adequate supply of accessible fish within a maximum of about 12 miles of the nest; open, usually elevated nest sites free from predatory mammals such as raccoons, and a long enough ice-free season to allow the young to fledge.
Fast Facts
Both sexes
Length: 21.3–22.8 in
Wingspan: 59.1–70.9 in
Weight: 49.4–70.5 oz
Relative Size: Smaller than a Bald Eagle; larger and longer-winged than a Red-tailed Hawk.
Food
The Osprey is the only hawk on the continent that eats almost exclusively live fish. In North America, more than 80 species of live fresh- and saltwater fish account for 99 percent of the Osprey’s diet. Captured fish usually measure about 6–13 inches in length and weigh one-third to two-thirds of a pound. The largest catch on record weighed about 2.5 pounds. On very rare occasions, Ospreys have been observed feeding on fish carcasses or on birds, snakes, voles, squirrels, muskrats, and salamanders. Ospreys probably get most of the water they need from the flesh of their prey, although there are reports of adults drinking on hot days.
Nesting Habits
Osprey nests are built of sticks and lined with bark, sod, grasses, vines, algae, or flotsam and jetsam. The male usually fetches most of the nesting material—sometimes breaking dead sticks off nearby trees as he flies past—and the female arranges it. Nests on artificial platforms, especially in a pair’s first season, are relatively small—less than 2.5 feet in diameter and 3–6 inches deep. After generations of adding to the nest year after year, Ospreys can end up with nests 10–13 feet deep and 3–6 feet in diameter—easily big enough for a human to sit in.
Ospreys require nest sites in open surroundings for easy approach, with a wide, sturdy base and safety from ground predators (such as raccoons). Nests are usually built on snags, treetops, or crotches between large branches and trunks; on cliffs or human-built platforms. Usually the male finds the site before the female arrives.
Behavior
Adept at soaring and diving but not as maneuverable as other hawks, Ospreys keep to open areas, flying with stiff wingbeats in a steady, rowing motion. Primarily solitary birds, they usually roost alone or in small winter flocks of six to ten. Nesting Ospreys defend only the immediate area around their nest rather than a larger territory; they vigorously chase other Ospreys that encroach on their nesting areas. In breeding season, males perform an aerial “sky-dance,” sometimes called “fish-flight.” With dangling legs, often clasping a fish or nesting material in his talons, the male alternates periods of hovering with slow, shallow swoops as high as 600 feet or more above the nest site. Sustaining this display for 10 minutes or more, he utters repeated screaming calls while gradually descending in an undulating fashion to the nest.
Migration
Resident to long-distance migrant. Most Ospreys that breed in North America migrate to Central and South America for the winter, with migration routes following broad swaths of the eastern, interior, and western U.S.
A few Ospreys overwinter in the southernmost United States, including parts of Florida and California.
Conservation
Ospreys are a conservation success story and their populations are still growing, aided by pesticide bans and the construction of artificial nest sites. Osprey numbers crashed in the early 1950s to 1970s, when pesticides poisoned the birds and thinned their eggshells. Along the coast between New York City and Boston, for example, about 90 percent of breeding pairs disappeared. Osprey studies provided key support for wider legal arguments against the use of persistent pesticides. After the 1972 U.S. DDT ban, populations rebounded, and the Osprey became a conservation success symbol. But Ospreys are still listed as endangered or threatened in some states—especially inland, where pesticides decimated or extirpated many populations.
As natural nest sites have succumbed to tree removal and shoreline development, specially constructed nest platforms and other structures such as channel markers and utility poles have become vital to the Osprey’s recovery. Sadly, a growing cause of death for Ospreys is entanglement at the nest: the adults incorporate baling twine and other discarded lines into their nests; these can end up wrapped around a chick’s feet and injure it or keep it from leaving the nest.
Additional Resources
- All About Birds, Cornell Lab of Ornithology: http://www.allaboutbirds.org/guide/Osprey
- DNR: Osprey (Pandion haliaetus) Species Guidance: http://www.dnr.wi.gov/files/pdf/pubs/er/er0680.pdf
- Wisconsin All-Bird Conservation Plan, Wisconsin Bird Conservation Initiative: http://www.wisconsinbirds.org/plan/species/ospr.htm
Sources: http://www.allaboutbirds.org/guide/osprey/lifehistory