Animal species have two general approaches to winter: migration and adaptation.

Migration. Many birds migrate by flying south. Some mammals and fish migrate to warmer climates. Even insects migrate. Some butterflies and moths fly great distances. Other insects, such as earthworms, termites and Japanese beetles, migrate by burrowing deeply into the soil to escape the frozen surface.

Adaptation. Other animals adapt to winter. Some grow thicker coats of fur to keep warm. Some, such as squirrels, mice and beavers, accumulate food in the fall to be eaten later. Others, such as rabbits and deer, continue to forage for leaves, twigs and bark to eat. And some, such as foxes, change their diet from fruits and insects in the summer to rodents in the winter.

Animals also adapt to winter by seeking shelter in places that can provide warmth, from an accumulation of leaves or a hole in a fallen tree to the attic of a house.

Skunks, woodchucks, raccoons, chipmunks and some squirrels reduce their need for food by slowing their metabolism through hibernation. The animal’s heart rate can drop by 95% and its body temperature can be reduced by more than 50%. If the ambient temperature drops too low, the hibernating animal will begin shivering to generate heat. Skunks, raccoons and some chipmunks are relatively light hibernators and awaken periodically to forage for food. Cold-blooded animals, such as snakes, frogs and turtles, cannot generate heat to keep warm during the winter and become dormant. Many insects also spend the winter in a dormant state.

More information on birds and other animals is available through the National Audubon Society, the Illinois Audubon Society, The Nature Conservancy of Illinois, the Lake County Forest Preserve District, and on the web.


When temperatures drop and snow falls, it’s natural to think that feeding wild animals is humane and helpful, but wildlife experts recommend against it. Except for feeding songbirds, putting out food for wildlife can be detrimental because the unnatural gathering of many animal species to one food source could promote the spread of disease and encourage predation. One way to help wildlife in winter is to avoid disturbing them. Animals must conserve their energy to survive winter, but human disturbance causes them to move about. Keeping dogs confined and slowing down when traveling in motor vehicles through deer areas will help animals survive.

Songbirds – Birds need both food and water during the winter. Many birds that winter in Riverwoods survive on the seeds produced in late fall by native grasses and wildflowers. Winter bird-feeding stations supplement the diminishing supply of seeds birds search for in developed areas. When providing seeds or suet for birds, feeders should be kept clean to reduce disease transmission, food should be kept dry, and moist, moldy food should be discarded. Feeders should be in close proximity to shrubby cover to protect the birds from predators and inclement weather.

Bird feeders should be placed at different heights to accommodate various species of birds. Some birds, such as sparrows and juncos, feed on the ground. Others, such as finches and cardinals, prefer raised feeders. Some birds flock to rigid feeders while other smaller and more agile birds prefer free-hanging feeders that sway in the breeze. Bird feeders should always be placed so access is difficult for squirrels and away from windows that could be a collision hazard for birds.

Birds are attracted to specific seeds. Sunflower seed is favored by a wide variety of birds, but birds prefer sunflower seeds with a high oil content, rather than the soft-shelled, low-oil sunflower seeds that humans consume. Many birds also like safflower seeds. One advantage of safflower seed is that it does not appeal to squirrels. In general, seed mixes usually contain fillers that do not appeal to most birds.

Even more helpful than keeping a bird feeder full of seeds is planting seed-bearing plants on which birds can feed throughout the winter. Native flowers, such as coneflowers, will keep seed heads through the winter. Some species of Viburnum shrubs bear large amounts of berries that will provide food for birds during the winter. Plants that do not provide food but that provide shelter, such as dense evergreens, are also valuable to birds during winter months.

Birds also require water. Ice and snow may not provide sufficient moisture for survival. Birds can’t rely on winter run-off from sidewalks and roads since the water is usually heavily contaminated with salt. One approach is to put out a large container of water daily or employ a heated birdbath.

Ducks and Geese – Feeding bread (fresh or stale) to ducks and geese is harmful to their health because it lacks nutritional value. Bread doesn’t contain much protein, which birds need to develop muscles and feathers, and it doesn’t contain the fat that birds need for energy. The same holds true for crackers, chips, cookies, and donuts. Instead, yards should be made wildlife-friendly with naturally grown food from trees and shrubs that yield nuts and berries.

Deer – Deer have developed adaptations that allow them to survive harsh winter conditions without human intervention, such as building fat and muscle during summer and fall, lowering metabolic rates during the winter and restricting movements during severe winter conditions to conserve energy. The digestive systems of free-ranging deer cannot use many types of artificial feed efficiently. Fruit and grains, especially corn and apples, can be extremely difficult for deer to digest, in addition to not having the nutritional value deer need to stay healthy. Instead, year-round quality habitat should be promoted so that animals go into the winter in good condition.

Some deer, especially fawns and older deer, will die in winter regardless of severity. Indeed, mortality among these age groups increases as winter severity increases. These animals usually have insufficient amounts of body fat and may be unable to find and compete with other deer for available food. However, the majority of deer will survive even the harshest winter without the need for supplemental feeding.