Canada geese that left a Chicago park returned twice as quickly when harassed, compared with days when they left of their own accord
© Copyright by GrrlScientist | hosted by Forbes
What should we do with all the geese? Canada geese, Branta canadensis, populations have exploded throughout Illinois, growing from an estimated 70,000 birds in 1997 to about 120,000 today. They are widely viewed as a nuisance: aircraft sometimes collide with them (remember Miracle on the Hudson?), they boldly intimidate joggers who get too close to their nests in springtime, and everywhere they go, they fertilize all those carefully tended lawns in parks, golf course greens, ball fields, airport infields and other green spaces by leaving behind prodigious piles of poop — a pound or more per bird per day.
What can be done to convince these large, poopy and often opinionated birds to just go away? The usual response is to rely upon dogs or humans to chase the geese until they leave for good. Wildlife harassment is a nonlethal method used to convince wild animals to leave a particular area by increasing their sense of danger if they remain. Winter harassment is especially popular in northern cities because the energetics of the situation suggest the geese would leave rather than starve.
“The goal of harassment is never to hurt the geese, but to get them to use up energy during an already tough season, forcing them to migrate to warmer climates”, said the senior author of the study, Mike Ward, a professor in the Department of Natural Resources and Environmental Sciences (NRES) with the University of Illinois at Champaign-Urbana. Professor Ward’s research focuses on species of conservation concern and he has developed a variety of novel approaches to accomplish his goal. For example, Professor Ward often uses telemetry to radio monitor the behavior and migration of birds.
“Harassment is part of an energy equation”, Professor Ward explained the logic underlying the harassment strategy. “If a bird is hanging around Chicago in winter, it’s probably not in good shape. It’s cold and doesn’t have a lot of food.”
And yet, according to previous studies, we know that harassment doesn’t work. The birds don’t leave. Why?
To answer this question, a large team of researchers fitted some Chicago-resident Canada geese with collars that carried GPS transmitters with Fitbit-like movement trackers to learn where they go and how their behavior changes when they’re being harassed.
Ward’s former doctoral student, Ryan Askren, now a postdoctoral researcher at the University of Arkansas-Monticello, collaborated with USDA-Wildlife Services personnel to harass Canada geese at Marquette Park near Midway Airport in Chicago (Figure 1).
During the winters of 2017 and 2018, members of the research team chased geese with ATVs whilst clapping wooden boards together to create a giant racket. The team predicted that the noise and the overall drama of the chase would be effective at dispersing the geese during winter, when food is in short supply and the demands to stay warm are at their greatest.
But things didn’t develop in the way the researchers predicted. The harassed geese either moved elsewhere in the same park or ended up hanging out on commercial rooftops, in nearby railyards or in other parks, in water treatment ponds, or sports fields for short periods of time before returning to where they started within an hour or less — almost two times faster compared to days when the geese were not harassed, when leaving the park was their own idea.
Why? Are they just stubborn? Stupid?
“When we harass them, it causes them to leave momentarily, but more than likely they still have that drive to come back”, Dr Askren speculated. “So they’re returning more quickly, whereas the geese that leave in the absence of harassment are staying away to make use of a resource elsewhere.”
What about the prediction that harassment in winter would deplete the geese’s valuable energy reserves and thereby encourage them to move on?
Dr Askren and Professor Ward and their collaborators didn’t find much evidence to support the energy prediction part of their study.
“I thought using these Fitbit-like devices on the neck collar was a creative way to understand resting, flying, or foraging behaviors”, Professor Ward stated. “And when Ryan was doing all this physical work to figure out what this accelerometry data would tell us, I was very eager to see what the results were”, Professor Ward continued. “But when all the data were analyzed, I was like, ‘Wow, that’s not too exciting’.”
“Basically, when you harass, they fly a little bit more because you’re scaring them, or they might be alert a little more, but it wasn’t a fundamental difference.”
Could the results have been different if the researchers had used a different harassment method? The scientists say this is possible, but the methods showing the most promise don’t usually go over well with the public. You know: lethal methods.
“The literature suggests unless there’s a lethal aspect to harassment, unless they really have a strong fear that they’re going to die or some of them are actually dying, then most harassment methods just don’t seem to be very effective”, Dr Askren said.
This could, in fact, be part of the reason that these geese do not migrate: they are afraid to face the gauntlet of gunfire from hunters.
Could being born and raised in a big city make geese nonchalant, or (dare I say it) unflappable? Dr Askren and Professor Ward had worked with these same geese for other studies, so they knew which geese were migrants and which were longtime Chicago residents. As they discovered, neither group was particularly disturbed by their chase and noise-making harassment histrionics.
Like so many human-wildlife conflicts, this is a human-created problem. People like gigantic lush lawns, and geese do, too. People like living on migratory flyways, where geese are sure to notice the easy, predator-free life they present. But there are a few things that private citizens do to keep geese off their grass. They can either completely get rid of their large lawn or reduce its overall size. Not only will this discourage geese, but it also is an environmentally sound response to a polluting and unsustainable drain on water and other resources. Another strategy is to plant trees and shrubs on your property so geese and their young are unable to flee from a threat by running to safety in a nearby body of water. Geese especially like wide-open spaces near bodies of water, like golf courses.
Canada geese are much like people in other ways, too. They are highly adaptable, they are intelligent and have an excellent memory, and they have a keen ability to distinguish between legitimate threats and mild annoyances.
“It’s why we likely won’t be rid of them anytime soon”, Dr Askren remarked.
“People don’t realize how smart geese are”, Professor Ward agreed. “They’ve learned what the real risks are over the course of their lives or from each other. Maybe we’ll figure out a good harassment technique, but it’s likely they’re going to continue to increase in urban areas because they found a good place. They’re nesting on top of buildings. I mean, who would have ever thought a goose would nest on top of a building? They should be nesting in wetlands. But they’re very adaptable.”
Ryan J. Askren, Mike W. Eichholz, Christopher M. Sharp, Brian E. Washburn, Scott F. Beckerman, Craig K. Pullins, Auriel M. V. Fournier, Jay A. Vonbank, Mitch D. Weegman, Heath M. Hagy, and Michael P. Ward (2022). Behavioral responses of Canada geese to winter harassment in the context of human-wildlife conflicts, Wildlife Society Bulletin 46(5):e1384 | doi:10.1002/wsb.1384
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