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Woodland Animals in Winter

January/February 2017

Submitted by the RPC


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

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.

Many 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 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.

Some animals, such as skunks, woodchucks, raccoons, chipmunks and some squirrels, adapt to winter by reducing their need for food by slowing their metabolism through hibernation. In some cases 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.

Birds – Birds need 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 deciding to set up bird feeders, they should be placed at different heights to accommodate different 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. Feeders must be kept free of wet seed or the seed will spoil and birds will avoid the feeder.

Not all seeds are attractive to all birds. Sunflower seed is favored by a wide variety of birds, but birds prefer sunflower seeds with a high oil content, rather than the softshelled, 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.

When deciding to put out bird seed, it is important to be consistent in feeding birds. Birds will circulate through an area, feeding at a variety of places, including bird feeders. If seeds are not regularly available in a bird feeder, birds will not become accustomed to visiting the feeder and will not visit it routinely.

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 seedheads 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, as indeed other animals, should not be fed bread, either fresh or stale, since it provides no real nutritional value. Bread doesn’t contain much protein, which animals need to develop muscles and feathers, and it doesn’t contain the fat they need for energy. The same holds true for crackers, chips, cookies, and donuts.

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. Again, consistency is a key to attracting birds.

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.


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