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Starve or die. For Canada geese, that’s a strategic choice.

Those big birds that hang out on city golf courses and playgrounds all winter have made a desperate gamble, according to a new study published in the Condor Journal of Ornithological Applications. They can hunker in food-free urban areas hoping not to freeze, or fly to forage in farm fields and hope not to catch a breastful of birdshot.

The problem is well-known to people like Bill Galiher, manager of Larchmont Golf Course in Missoula.

“We know it's hunting season,” Galiher said. “As soon as the golf would slow down, it doesn’t take them long to figure it out. And when we have a lot of snow, they hang out under the trees and eat all that grass. We have a hard time growing it back.”

The study put radio transceivers on 41 of the estimated 30,000 geese wintering in and around Chicago from 2014 to 2016. The researchers used “rocket nets, cast nets, and small animal net guns” to catch the birds. Because the study also looked at aircraft collision risk, many were caught near Chicago’s Midway International Airport as well as in parks, cemeteries and the Stickney Water Reclamation Plant.

They learned that while there wasn’t much food in the city landscape, geese used some clever tricks to survive. Many spent time in railroad yards, possibly looking for grain spilled from freight cars. They also perched on city rooftops, taking advantage of the building heat. All the geese that stayed in the Chicago urban area survived the winters.

But half the birds that flew to farm fields less than five miles away died in the process.

"The growth of urban areas and northward expansion of row-crop agriculture have changed the way geese migrate. Unfortunately, some of our large cities have become goose sanctuaries, where resident geese and migratory geese congregate during winter to escape hunting pressure," said study co-author Heath Hagy of the University of Illinois at Urbana-Champaign. "Although additional research is needed, our data will be useful to guide goose harassment efforts, which may offset the benefits of remaining inside urban areas during winter and open hunting seasons."

As migratory game birds, Canada geese are illegal to kill without a license, and always against the law to do so inside city limits. As with urban deer, that limits the options for grounds managers trying to keep the winter interlopers from causing trouble.

“We try to chase them off, but they go from one side of the golf course to the other,” Galiher said. “They know we’re not killing them.”

On the other hand, having those geese in town isn’t just a matter of avian trespassing. The study noted “geese in urban areas can pose threats to humans, including contamination of water sources, aggressive behavior toward humans, disease transmission, and strikes with aircraft. Geese are the largest bird commonly struck by aircraft in North America, and were responsible for 1,403 recorded bird strikes to civilian aircraft from 1990 to 2012.”

While geese can endure long periods without food, cold winter temperatures stress their energy resources. The researchers concluded there could be a tipping point where seemingly ineffectual efforts to make them leave might actually pay off.

“Harassment of geese during cold periods may ‘push’ geese to the point where they have to choose to either move or potentially risk death due to increased energy demands,” the study authors wrote. “However, we acknowledge the logistical and social challenges related to harassment of geese in urban areas. Population management outside of winter may be necessary to reduce human-wildlife conflicts.”

Easier said than done.

“We’ve tried sprays and decoys, but they just get used to it,” Galiher said. “You can spend all that money and then they’re right back at it. Short of opening up a gun club, which we’re not going to do, although we’ve been asked about it, we just live with the mess and the grass damage. They’re beautiful, but they’re also a pest.”