StoryImage( ‘/Images/Story//Auto-img-110917566411137.jpg’, ‘Photo by Dr. Robert A. Hedeen’, ‘The snowy owl occassionally visits the Rock River Valley during winter.’);
During a respite in the frigidly cold weather the Rock River Valley experienced the middle of January, I took a short hike around Rock Cut State Park. Numerous ice fishermen were set up on the frozen lake, and that seemed to be the extent of the animal activity in the park. Glancing around the landscape, I was stunned to see a large white bird sitting on the limb of an oak tree. I immediately recognized it as a snowy owl.
This was only the second time I had seen one of these infrequent visitors from the northland. The previous sighting was sometime back in the 1960s when I lived in south Cook County, and one cold, snowy morning I looked out of a back window and saw a magnificent snowy owl sitting nonchalantly on the wooden fence in my backyard. It was quite a thrill to see another one after all those years.
This owl is found in the arctic and is circumpolar in its distribution. It is the heaviest of North American owls and may stand more than 3 feet tall and have a wing span of up to four feet. Adult males are almost pure white in color, but the adult females are darker, having the feathers barred with brown. Immature owls are much darker than the adults and may appear gray when viewed from a distance. The light coloration is advantageous when the owls are perched on snow, but the protection of camouflage is lost in the summer. These formidable birds really dont need camouflage as they are well able to take care of themselves if an arctic fox is foolish enough to decide he wants one for dinner. The large yellow eyes are surrounded by batches of stiff feathers that reflect sound waves to the ears. This acute sense of hearing helps the bird to locate prey in dim light. Their stereoscopic vision is very sharp.
They are well adapted for life in the arctic as the thick feathering overlays a dense layer of down that covers the entire body including the legs and toes. This enables them to maintain a body temperature of around 100 degrees, even when the temperature may plunge to 50 below.
Their homeland is the arctic, but they regularly migrate south during the winter to southern Canada. They are cyclic migrants to the United States, and do not come that far south with any regularity. They have been spotted infrequently, however, as far south as central California and from Texas east to Georgia.
The preferred food of the snowy owl is rodents, and it has been estimated that it must capture the equivalent of seven to 12 mice a day (as many as 350 per month) to meet its metabolic requirements. Although they are fast enough to capture ducks on the wing, snowy owls prefer mammals as prey. In the arctic they may eat hares, ptarmigans, or sea birds when available, but, their favorite tidbit is the lemming, which resembles a large field mouse. On their winter range, snowy owls also feed mainly on small rodents such as voles and white-footed mice. A snowy owl, however, is an opportunistic hunter and will take anything it can overcome; from shrews to jackrabbits, and birds, from sparrows to ducks and pheasants.
These owls, like other birds of prey, swallow their meals whole. Strong enzymes digest the meat, and the indigestible teeth, bones, fur, and feathers are compacted into pellets that the bird regularly regurgitates. Regurgitation usually occurs at a favorite resting spot where dozens of these pellets may be found. As with other owls, biologists examine the pellets to determine the quantity and types of prey animals.
As noted, the snowy owls have few predators except man. Years ago, they were routinely shot when wintering in southern Canada as they were thought to be a menace to poultry and other farm animals. These days, however, most people prefer to shoot the snowy with a camera instead of a gun. The snowy owl is not protected by the Migratory Birds Convention Act of Canada. However, provincial and territorial regulations make it illegal to kill one of these birds anywhere in Canada. When they venture south of the border to the U.S., they help in the natural control of harmful rodents in agricultural areas.
One good thing that comes out of our sometimes harsh winters is that a snowy owl just might drop in for a visit, no passport or visitors visa required.
Dr. Robert Hedeen is a former resident of Marylands eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.