Wisconsin winters bring extreme cold and snow, challenging local wildlife. However, not all bird species migrate south. A resilient group of permanent and seasonal residents remains in the state, relying on specialized adaptations and local food sources to endure the long, frozen season.
Reliable Year-Round Wisconsin Residents
The most predictable winter bird sightings come from species fully adapted to the cold, maintaining a year-round presence. The Northern Cardinal, with its bright red plumage, is a fixture in brushy areas and suburban backyards. Cardinals prefer black oil sunflower seeds, which provide the high-fat content needed to fuel their metabolism in frigid air.
Small, active species like the Black-capped Chickadee and the White-breasted Nuthatch are also dependable residents throughout the winter. Chickadees are frequently seen flitting between branches and visiting feeders, consuming up to 35% of their body weight daily to maintain their high body temperature. Nuthatches, in contrast, are often observed descending tree trunks head-first, foraging for dormant insects and wedging seeds into bark crevices.
Woodpeckers, including the Downy and the larger Hairy Woodpecker, remain active through the season, clinging to tree bark in search of insects and larvae. The Downy Woodpecker is the smallest and most common, easily attracted to suet feeders in wooded areas. The Red-bellied Woodpecker has also expanded its range and is now a common sight, accessing insects that other species cannot reach by drilling into wood.
How Birds Survive the Deep Freeze
The ability of small birds to survive the cold of a Wisconsin winter is due to physiological and behavioral adjustments. One of the most energy-intensive strategies is shivering, a rapid, involuntary muscle contraction that generates metabolic heat to maintain a core body temperature near 100 degrees Fahrenheit. This process is so demanding that a Black-capped Chickadee, for instance, must spend nearly all daylight hours foraging to replenish its energy stores.
Birds also use their feathers for insulation through a process called piloerection, where tiny muscles fluff up the plumage to create air pockets that trap warm air against the body. This puffing action maximizes the effectiveness of their downy underlayer, minimizing heat loss. To protect unfeathered extremities, species that stand on ice or cold ground, such as waterfowl, employ a countercurrent heat exchange system in their legs, which cools the arterial blood flowing to the feet while warming the venous blood returning to the body.
Behaviorally, many small songbirds cache seeds during the autumn and early winter, relying on spatial memory to retrieve them later when food is scarce or buried under snow. They also seek out sheltered roosting spots, such as dense evergreen boughs, tree cavities, or roosting boxes, sometimes huddling together in groups to share body heat. In the most severe cold, a few species can enter a controlled, short-term state of torpor, temporarily lowering their body temperature and metabolic rate to conserve energy reserves.
Northern Irruptions: Sporadic Winter Visitors
Beyond year-round residents, certain winters bring irruptive visitors, whose presence is irregular and depends on food availability further north. These irruptions occur when conifer cone or berry crops fail in the boreal forests of Canada. This forces finches and other northern species to move south into Wisconsin in search of sustenance.
Irruptive finches often congregate at feeders offering high-fat seeds. These resource-driven migrations include:
- Common Redpoll, a small, streaky bird with a red cap.
- Pine Siskin, which often travels in large, twittering flocks.
- Evening Grosbeaks, large yellow-and-black finches with massive bills.
- Various Crossbills, named for their unique crossed mandibles used to extract seeds from cones.
Larger irruptive visitors from the far north sometimes include the Snowy Owl, which descends from the Arctic tundra to find food when lemmings and other prey populations crash. These owls seek out large, open expanses that mimic their native treeless habitat, such as agricultural fields or lake shorelines. The Northern Shrike, a predatory songbird, is another sporadic visitor that hunts small birds and rodents in open country.
Providing Support for Overwintering Birds
Individuals can aid overwintering birds by providing high-energy food sources that compensate for scarce natural forage. Black oil sunflower seeds are favored by chickadees, nuthatches, and cardinals due to their high fat content and thin, easily cracked shells. Suet, rendered animal fat, is another source of concentrated energy, particularly appreciated by woodpeckers and nuthatches.
Finches like the Common Redpoll and Pine Siskin are attracted to thistle, or Nyjer, seeds, which are best offered in specialized tube feeders. Offering a variety of foods ensures the needs of different species are met. Consistent access to clean, liquid water is also important, often provided using a heated bird bath to prevent freezing.
Providing adequate shelter from the elements and predators is important alongside food and water. Dense stands of coniferous trees or thick brush piles offer windbreaks and safe roosting areas for small birds during severe weather. Simple roosting boxes can also be installed to mimic natural tree cavities, allowing birds to conserve body heat during the deep freeze.