Chicago, Illinois, is a sweet home for more than just Cubs fans and blues hounds. According to a new study, the Windy City is a safe haven for migrating Canada geese, which are twice as likely to survive the winter there than geese that forage in nearby rural areas. But what’s good for the goose isn’t necessarily good for the gander: As more of these large birds overwinter in North American cities, the chance for conflicts with humans is taking off.
The Canada goose spends its summers in Canada and the northern United States and its winters in the southern United States and northern Mexico. But as the climate heats up, the geese are wintering farther and farther north. This means they don’t expend as much energy on migration. But the real boon for the birds has happened in the past 50 years or so. They’ve started moving into cities like Chicago, which are generally warmer than the countryside, studded with large lakes and parks, and safe from human hunters.
To quantify the trend—and figure out how the flocks might be affecting people—scientists attached radio transmitters to 41 adult geese in the greater Chicago area in the falls and winters of 2014–16. Ecologist Heath Hagy of the University of Illinois in Champaign and colleagues identified where the birds went and when, based on location data from the transmitters. As winter progressed, most of the geese moved from open parks to lakes and industrial zones, where it was warmer and easier to forage for food. Few geese ventured outside the city to the nearby fields, where food would have been much easier to find.
Of the birds that foraged in the country, just 48% made it through…