A pair of mute swans swam in slow circles in the stinking water of the Chicago River near the Diversey bridge. It was an incongruous scene–the majestic birds floating like huge white flowers in the gritty divide between a bowling alley and a public-housing project.
Best of Chicago voting is live now. Vote for your favorites »
The pair near the Diversey bridge, which I first spotted in January, were probably the only mute swans on the river this winter, says Doug Stotz, an ornithologist and conservation ecologist at the Field Museum. “Swans are territorial in the breeding season, not in the winter, when you can get big flocks together,” he says. “My guess is that the one pair at Diversey is a reflection of the fact that it is a narrow river and not stupendous swan habitat rather than territoriality.”
The river flows all winter, giving the swans the open water they need. It also has vegetation these herbivores can eat. Stinky as the river is, Stotz says, the weeds in it accumulate relatively low amounts of pollution. If the swans chose to stay beyond March, the riverbanks would offer places where they could nest.
Beautiful as they are, swans are cursed in the northeast. More than 9,500 mutes winter in Pennsylvania, and according to a report by Pennsylvania State University’s extension service, these itinerants are solitary and aggressive, greedily consuming aquatic vegetation that fish and other wildlife need. And their droppings litter green spaces and “can limit recreational use of the area.” The report details lethal and nonlethal ways to get rid of swans.
Most cygnets don’t make it past their first year. “It’s tough being a young bird,” says Stotz. “In most species the vast majority of young do not survive to age one. Predation of flightless young–so less than about four months old–and then starvation or disease in older young are probably the major causes of deaths.” If a mute swan survives its first year it lives an average of six years, though about a quarter of the birds make it to ten.
