Forest Preserve District of Cook County, Illinois
Nature Bulletins
Newton Home Page

Introduction and Instructions

Search Engine

Table of Contents



Wildlife's Winter Diet
Nature Bulletin No. 659   December 9, 1961  
Forest Preserve District of Cook County 
George W. Dunne, President
Roland F, Eisenbeis, Supt. of Conservation

Anyone who regularly feeds wild birds, and counts up the amount of food that they eat in the course of a winter, often wonders how they could get along without his help. In one day of freezing weather two or three dozen small birds commonly clean up a half pound of food -- suet, sunflower seed, cracked corn or small grain. This does not take into account raids by squirrels and rabbits.

Winter in this region is a time of food crisis for all warm-blooded wildlife. Most of our summer song birds, especially the insect eaters, avoid cold by migrating to warm climates until spring. Likewise, most waterfowl and shorebirds go south during the months when our waters are locked in ice.

A few native mammals such as woodchucks and ground squirrels are true hibernators. They prepare for winter by putting on extra fat which they can draw on slowly during the cold months. In autumn they hide away underground beyond the danger of freezing and "sleep" until spring. Among these winter sleepers body temperatures often drop to 40 degrees Fahrenheit and their life processes are slowed to a crawl. In dormant woodchucks, for example, the heartbeat can drop from 80 per minute to four, and breathing from 25 per minute to once in five minutes.

The raccoon, opossum and skunk commonly hole up and stay quiet for a few days or even weeks during extremely cold weather. Then they live on their fat reserves but do not become cold-blooded. On warmer nights they come out and forage actively even in midwinter. The raccoon feeds on waste corn in farmers' fields, acorns and wild fruits, or searches the shallows of unfrozen streams for crayfish. In addition to scavenging for any kind of animal matter, the opossum eats wild fruit, The skunk hunts meadow mice, ground-roosting birds, and digs among grass and fallen leaves for hibernating insects.

Some animals hoard food for winter use. In autumn, chipmunks and deer mice gather large quantities of nuts, wild cherry, basswood, dogwood and other seeds which they store in their burrows. The fox squirrel and gray squirrel bury nuts and acorns in the ground near their den trees. In winter these are dug up and eaten, even through inches of snow.

Before freezing weather sets in, the beaver gnaws down cottonwood, aspen and willow trees, then cuts the branches into convenient lengths and sinks them underwater for winter use. The muskrat feeds under the ice on the roots and stems of cattails and other aquatic plants but it also piles up special mounds of plants in early autumn which are eaten in winter.

All of the winter birds and many of the mammals of our region face the necessity of finding enough food each day to keep themselves alive and warm until the next day. Their diet may vary from day to day and place to place, depending on what can be found. Also, many have their own likes and dislikes.

The meat-eaters -- hawks, owls, foxes, weasels and mink -- catch a few birds but their mainstay is meadow mice and an occasional cottontail rabbit. Both of the latter are strictly vegetarians. The mice scamper about in a network of tunnels under the snow as they nibble on grass. The cottontail munches on clover, tender plants, waste grain or gnaws the bark from shrubs and young trees.

Weed seeds, wild berries and acorns offer an abundance of natural food for the majority of our winter birds. Others search the trees and thickets for dormant insects, their eggs and larvae.

The big black noisy crow is the cleaner-upper of our highways and picnic areas .

To return to the Nature Bulletins Click Here!
Hosted by NEWTON

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Sponsered by Argonne National Labs