Forest Preserve District of Cook County, Illinois
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Nesting Habits of Owls
Nature Bulletin No. 624   January 14, 1961
Forest Preserve District of Cook County
Daniel Ryan, President
Roberts Mann, Conservation Editor
David H. Thompson, Senior Naturalist

NESTING HABITS OF OWLS
From all of the information available it appears to us that, amongst the owls, there is greater variation in where and how they nest than in any other group of birds.

Two nesting characteristics, however, are common to all owls. The eggs are nearly spherical and white, or off-white, without any markings. Also, a nesting female does not lay one egg per day, as most birds do, but at intervals of two or more days -- sometimes several. In extreme cases there may be a fresh egg, others incubating, and a newly hatched fledgling -- all in the same nest.

Of 14 species native in North America, seven are more or less common here in the Middle West. However, one of these is the most widely distributed of all land birds: the short-eared owl nests in marshy or open grassland country from the Arctic south to Patagonia and the Falkland Islands near the southern tip of South America. Four species nest only in the Arctic but occasionally visit our northern states during winter.

Six species commonly nest in trees, using and enlarging an old nest of a hawk or some other large bird. Three small kinds -- the screech owl so common here; the saw-whet owl, less common; and the pigmy owl found in our western states -- habitually nest in hollow trees or cavities excavated by squirrels and woodpeckers. The snowy owl of the Arctic tundras, and the short-eared owl, always nest on the ground in a slight depression lined with grass and their breast feathers.

The burrowing owls are unique in that they nest underground. The western burrowing owls is a comical, long-legged little fellow that inhabits prairies and unforested places from Manitoba and Saskatchewan in Canada to Mexico, Guatemala and Panama. It uses the abandoned den of some burrowing mammal such as a badger or a skunk but especially "prairie dogs". They also enlarge and use the burrows of ground squirrels and gophers. The Florida burrowing owl digs its own burrow, from 4 to 10 feet long, in the soft soils of the palmetto prairies in central and southern Florida.

The elf owl, also called the monkey-faced owl because of its peculiar white heart-shaped face, is a common resident in most parts of the United States. A barn owl will nest in almost any dark sheltered place, including tree cavities, caves, old mine shafts and even burrows, but they are partial to barns, attics of old buildings, water towers and church belfries. Although they do not build a nest, a pair may use the same site year after year. The barn owl is our greatest destroyer of mice, rats and other rodents.

The great horned owl is the largest, most powerful and fiercest species native in the Chicago region and the largest one with ear tufts. They never build a nest but, in some deep wild woodland, take over one built by a hawk or a heron. Of all our birds, they are the earliest to nest. We have seen a female, covered with snow, solidly incubating her eggs during the first week of February. Unlike other owls they lay only two or sometimes three.

All owls are beneficial predators protected by law in Illinois but the great horned owl was not included until 1959 because, in addition to rats, rabbits and crows, this "tiger of the air" also preys on game birds and poultry.


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