The red-shouldered hawk occasionally winters in Wisconsin, and can be found throughout the state in mostly forested habitat, though most birds migrate south for the winter. At Everglades National Park earlier this month, I was able to see red-shouldered hawks in a different habitat than they use in Wisconsin, as these Florida birds soared in their characteristic Buteo style over the open sawgrass glades.
The diet of the red-shouldered hawk speaks to its adaptability. Currently, wintering Wisconsin birds will hunt small mammals, mourning doves, house sparrows, and starlings, in addition to carrion. Winter birds have also been noted at feeders. Habitat for overwintering birds changes a bit from breeding habitat, as the hawks will occupy more fragmented landscapes like woodland edges, parks, and even suburban or urban residential areas.
By mid-February, the hawks will start migrating north to establish territories. The habitat most associated with breeding red-shouldered hawks is mature lowland forest, though contiguous areas of upland forest, like the Kettle Moraine, will also provide breeding habitat. Most important to the hawks are water features, and ephemeral ponds of the Kettle Moraine provide good substitute for the typical riparian habitat.
With the return to breeding grounds in mid-February, the hawks typically coincide with the emergence of chipmunks from hibernation. This marks an important food source for the birds year-round, but especially at this time of year. It is thought that chipmunk population cycles might play a role in the breeding success of red-shouldered hawks.
Once the snow thaws, the adaptable diet of red-shouldered hawks really stands out. One study in Iowa found that during a dry year, 92% of prey items delivered to nests were small mammals. During a wet year, 85% of prey items were amphibians and arthropods. Nesting in these dynamic and productive lowland forests, red-shouldered hawks are able to maneuver between different prey items to suit their needs. They'll even supplement their diet with crayfish and fish. Consuming amphibians as an important part of their diet, these lowland forests and ephemeral forested ponds—noted for amphibian abundance—provide ample hunting opportunities for these birds.
Red-shouldered hawks show a high site fidelity, and will oftentimes return to the same nest 3 to 4 years in a row. They typically form long-lasting pair bonds. Nests are typically built in massive trees, often red oaks in Wisconsin, built more than halfway up the tree and lined with conifer sprigs upon spring arrival. In areas like southern Wisconsin where evergreen leaves are hard to find, the resourceful hawk might decorate with birch bark or mosses or lichens.
Viewing the red-shouldered hawk's distribution in Wisconsin on eBird, one sees some major veins of observations: the Wolf River, Chippewa River, Wisconsin River, Mississippi River, and Kettle Moraine. These large river and forest systems have intact and contiguous floodplain forests to support these birds. Cutting of forests, even small-scale selective cutting, can have detrimental effects on red-shouldered hawk nesting habitat since red-tailed hawks and great horned owls will displace red-shouldered hawks as habitat becomes more fragmented.
Here at Faville Grove, the red-shouldered hawk habitat is rather lacking, as the open landscape and lack of contiguous forest cover discourages these birds from nesting. However, it wouldn't be out of the question to see a red-shouldered hawk here during the winter. Additionally, the opposite side of the Crawfish River historically supported rich deciduous forest, with the Crawfish serving as a firebreak between the prairie on the western side and forest on the east, and it's not hard to imagine the terrific habitat such a forest would have provided.
Written by Drew Harry, Faville Grove Sanctuary land steward