Winter in Chicago is legendary. Lake-effect snow, wind chill, polar vortexes—those of us who live here are a hardy breed and used to such things. We’ve become well adapted to crunching over salt on the roads, shoveling out our parking spots, and layering our clothes and our coats.
Local wildlife also adapt to the chilly conditions in the region. If you’ve ever wondered what animals do in the winter at Nature Boardwalk and in your own Chicago neighborhood during that period of time that has us all retreating indoors from November to April, here’s what you need to know.
Unique Birds Visit
Peak migration is over for many bird species, but December and January bring special visitors to the area, such as snowy owls, crossbills, and enormous flocks of migrating sandhill cranes. The snowy owls that captivated crowds at Montrose Beach in late 2025 arrived all the way from the Arctic in late November and stayed through about mid-December. The beginning of spring migration comes in February; it starts with the return of migratory waterfowl and includes the abundant and territorial red-winged blackbird, which makes an early arrival back to the area.
In this region, bald eagles can be spotted roosting in December and remaining all the way through March. In fact, Illinois hosts more than 3,100 bald eagles during this time, which is the most of any state outside of Alaska. January and February are optimal times for viewing the eagles as they winter at their breeding grounds in areas with open water, such as along the Illinois River.
Of course, some bird species are permanent residents of the area; they are able to find adequate food and shelter and can handle the cold. You’ll find robins, cardinals, woodpeckers, goldfinches, bluejays, and black-capped chickadees among them.
Bird at Nature Boardwalk. Image courtesy of Brendan Daley.
At Nature Boardwalk, eight bubblers help keep the water in the pond from completely freezing over, which makes it a good resource for local wildlife that may find it more difficult to find liquid freshwater this time of year. Around these bubblers, you may see different species of birds, especially waterfowl. Some, like red-breasted mergansers and common goldeneyes, even overwinter here starting in November and December.
Living Wildlife Friendly
Lincoln Park Zoo, a natural gem in a big metropolitan area, is home to the Urban Wildlife Institute, which includes researchers whose work is designed to help us coexist with city animals. If you’re looking for ways in which you can foster positive experiences with wildlife in Chicago, they recommend observing without disturbing animals, reducing waste and securing your trash, building wildlife habitat where you can, and spreading the word. Learn more here.
Reptiles and Amphibians Stay Dormant
As ectothermic (cold-blooded) animals, most reptiles and amphibians cannot produce their own body heat. This makes remaining dormant or inactive during the winter a good survival strategy for them. Many overwinter by burrowing underground or underwater. They undergo a process called brumation, a lighter form of hibernation, beneath the frost line (the maximum depth at which groundwater in soil will freeze). In response to triggering stimuli such as cold weather, their metabolism, activity levels, and heart rate slow, but they may remain conscious and even active.
When temperatures remain more consistently below freezing, reptiles and amphibians will stay dormant. Of course, different species have different survival strategies. The wood frogs of Cook, Lake, and DuPage counties, for example, freeze themselves nearly solid to make it through the winter, hiding in leafy litter on forest floors. They stop breathing and their heart stops beating while natural antifreeze compounds in their cells (created in the frog’s liver from large amounts of glucose) prevent ice from forming. In the early spring, they thaw out and hop right back into action.
Mole salamanders are the most numerous salamander species in Illinois. And although many local amphibian species remain dormant through February, mole salamanders begin migrating to seasonal wetlands during that month from their forest habitats to find mates. These migrations may involve road crossings, especially on rainy evenings, so be aware when traveling during these times.
Nature Boardwalk is home to amphibians such as the American bullfrog, which hibernates in the winter, and green frogs, which overwinter as tadpoles. Turtles such as the painted turtle brumate on the bottom of the pond until spring.
Fish Become Inactive
Like reptiles and amphibians, fish are ectotherms. They act much the same way as reptiles in winter, staying inactive throughout the coldest months of the year. In their winter resting state, their need for food and oxygen decreases.
In December at Nature Boardwalk, fish species start to school together in the deeper portions of the pond, protected by the insulated layers of ice that start forming when the temperature decreases. Some species also burrow into soft sediment and go dormant. Among the species you’ll find here are bluegills, pumpkinseeds, and largemouth bass.
Insects Have Diverse Strategies, From Diapause to Migration
Like other cold-blooded life forms, insects stay dormant or inactive throughout the winter—but they also have diverse strategies for survival. Some migrate; some die in the fall and depend on their offspring to survive the next year; some may stay active all year round, if they live in your house (think spiders). Some enter a form of dormancy called diapause in which they slow their metabolic activity to conserve energy, and tuck themselves into tree bark, in the ground, in leaf litter, and similar places to ride out the season. Many overwinter not as adults, but in various other stages of life.
For Illinois bumblebee species, fertilized adult queens overwinter in underground nests. Other bumblebees have short life spans, so she is the only survivor, and will repopulate the colony in the spring. Additional native bee species are in various life stages when they go into diapause. They seek refuge in underground burrows or natural cavities as solitary animals. Meanwhile, honeybees huddle around the queen within their hives and vibrate to generate heat. This requires a lot of energy, so they must have a large reserve of it—in the form of honey—available to them.
Meanwhile, most butterfly species overwinter as eggs, larvae, or pupae. Many non-migratory ones will be survived by their offspring, which overwinter in specialized chrysalises, often made of a leaf from their host plant. A few, like monarch butterflies, travel long distances as they migrate. In fact, monarchs are the only butterfly that make a two-way migration and come back and forth from Mexico and California. Painted lady butterflies undertake the longest migration, from West African to South America—a distance that can clock in at more than 4,200 miles. The individuals that return are not the same ones that left, though, making theirs a one-way trip.
Ticks, which hide out under layers of leaves, aren’t affected by cold weather unless the temperatures are under 10 degrees Fahrenheit for days at a time and they haven’t taken shelter. Ticks can produce antifreeze proteins to help them tolerate deep-freeze conditions. Mosquitoes overwinter as eggs, and the eggs of many species are hardy enough to survive extreme cold when sheltered. Asian tiger mosquitoes, for example, switch to laying diapause eggs in the fall; these include lipids that insulate embryos from cold and have a reduced metabolism. For these reasons, climate change will likely make tick and mosquito populations and the diseases they spread more difficult to control.
How to Tell Beavers and Woodchucks Apart
From a distance, beavers and woodchucks (groundhogs) can be difficult to tell apart. But there are a few things to look for that can help you make an identification. To start with, woodchucks and beavers are not closely related. Woodchucks are from the same genus as marmots and are like large squirrels; beavers are semiaquatic mammals that have been seen at Nature Boardwalk. The main visual distinguishing feature between the two are their tails: The tails of groundhogs are long, rounded, and furry; the tails of beavers are flat and leathery in appearance, with a scaly pattern.
But there are also other differences. Beavers are generally larger than woodchucks, weighing up to 60 pounds compared to a woodchuck’s average of about 10 or 15. Beavers, which eat trees and bark as well as aquatic plans, are found near bodies of water, as they have adaptations such as webbed feed that make them more comfortable there. Woodchucks prefer well-drained land. They are burrowers, and they eat a more omnivorous diet.
Plants Adapt
Plants have developed numerous adaptations to survive winter in the Chicago area. Annual plants only survive for one season, but their seeds germinate and may actually require a period of cold weather to bloom in the spring. Bienniels, which grow for two seasons, produce leaves at the ground level that are less susceptible to cold, especially if they end up being insulated under a blanket of snow.
Perennials, such as broad-leafed trees and shrubs and herbaceous plants, go dormant. Their food is stored in their roots, and they live off that all winter until they bloom in the spring. These deciduous plants drop all their leaves, which helps them retain moisture and reclaim nutrients. Some of these plants become “hardened”—that is, water gets pumped out of plant cells into the roots and any remaining sap moves outside of the cells and becomes concentrated, acting like antifreeze.
Many tree species undergo an acclimation process at the cellular level, allowing them to survive in colder temperatures, which determines where they live. So the ones that survive in the Chicago area are well adapted to winters here. Trees with broad leaves, including maples and oaks, shed their leaves and become sealed at the attachment point to reduce water loss.
Meanwhile, evergreen conifers retain many of their needle-like leaves, which have a waxy coating along with tighter stomatal closures (like pores, allowing water and air to pass in and out) that help reduce water loss. Conifers continue to photosynthesize in winter, but at a slow rate.
At Nature Boardwalk, the zoo’s Horticulture team maintains the area with incremental, controlled fires in the prairie ecosystem. Fire is a natural part of prairie ecology that helps recycle underbrush, remove excess plant litter, and revitalize the soil with nutrients. Once that is done, the prairie lies dormant with seeds dispersed and underground root systems surviving although their aboveground structures have withered away. For plant species like milkweed, this cold inactive period is quite critical; the transition from cold to warm during the spring thaw is what catalyzes the seeds to sprout.
Mammals Operate on a Spectrum of Activity
Some mammals, such as coyotes and squirrels (red, gray, and fox) remain active throughout the winter season. Others, like beavers, cache food for themselves, hide away, and are only periodically active. Some species, like ground squirrels and bats, hibernate for longer periods of time; they are only active for a little bit all season.
Most mammals in Illinois—including coyotes, raccoons, squirrels, bats, and skunks—enter their breeding seasons from January to March. Their activity levels increase to provide enough sustenance for parents as well as gestating young. Mammals that have faster gestation periods, such as tree squirrels, can start giving birth as early as February. You may start to see increased foraging activity outside of animal dens next month. Mammals that you can spot at Nature Boardwalk include gray squirrels, muskrats, woodchucks, chipmunks, and even—in recent years—beavers.
Coyote tracks. Image courtesy of Zoo Porgrams Manager Marisa Shender.
What Do Squirrels Do in the Winter?
A bit like humans, eastern gray squirrels spend more time in their dens and put on “layers” by bulking up. As they prep for winter each fall, they maximize food consumption and develop fat reserves. They also collect stashes of food they can draw upon during the colder months. They spend time in dens with other squirrels, helping to keep each other warm. Squirrels also shiver—an action that helps them keep warmer.
