I recently read something about the biology and ecology of geese that could be important to understand when thinking about “managing” them in open spaces – especially what contributes to the overabundance of geese and why its so hard to scare them away.
In the first half of the 20th century, Canada geese were captured and used as live decoys in the hunting of migratory geese populations. They had their wings clipped, so they couldn’t return to Canada and ended up breeding here to contribute to a population of “resident” geese. By the 1960’s, hunting threatened the migratory Canada geese population with extinction and the resident flocks were mostly gone. To counter this near extinction, the US Fish and Wildlife Service and many State wildlife agencies began a program of re-population of wild Canada geese. Like many “be careful what you wish for” situations, the program was super effective and by the early 1990’s this re-population effort was halted because it resulted in large resident geese populations in cities and suburban areas.
Unfortunately, the geese born as a result of the Canada geese repopulation effort do not have the imperative to nest in Canada since they were born here. Since geese return to the area where they were born to nest, and also mate “for life”, the population of geese we’re dealing with in our parks are essentially “residents” just like us. That’s why it may seem that geese “don’t seem to migrate anymore”.
Resident Canada geese nest in the early spring and have their goslings in May.
Goslings
After nesting, geese undergo an annual "molt", a 4-5 week flightless period when they shed and re-grow their outer wing feathers. Molting occurs between mid-June and late July, and the birds resume flight by August. Geese need a “safe” location to molt- generally is an area which has a water body for sanctuary (they can’t fly but they can still swim and their strategy is to flee into the water to escape predators) and nearby grass for food. Ouropen spaces are often the perfect habitat for molting. Goslings can’t fly either until mid to late August.
This means that geese and goslings are biologically “trapped” in the area where they nested, were born and/or molted because they are flightless – they can’t leave until early to mid August when they are able to fly again. This is why it seems that no matter what we do to try to scare them away they don’t leave - in fact, they can’t! Unfortunately, this period coincides with the start of the spring active outdoor activities and continues into summer vacation times when people are outside.
There are a number of different ways to “deter” geese, but most don’t work. Some of the best “ecologically-based” methods aren’t feasible for most open spaces – like replacing turf lawn with tall grasses (geese forage on mowed lawns). Vegetated shorelines are unattractive to geese because they can’t see potential predators when swimming and they can’t quickly access the water from the land, so wildlife biologists recommend planting water edges with native riparian vegetation like willows, sedges, and rushes. But obviously we can’t do that everywhere.
One approach is treating the grass so that it is unpalatable to the geese and forces them to go elsewhere to find grass to eat. This approach could deter young geese and geese without goslings from choosing our parks as a safe location for molting, and maybe even deter nesting.
Two chemicals are approved for use by the Food and Drug Administration as Canada goose repellents: methyl anthranilate (MA) and anthriquinone. MA is a non-toxic taste aversion agent derived from grapes. Treatment of vegetation with MA makes it unpalatable to Canada geese. MA is safe for human consumption, so it can be used on crops where necessary. Products with MA as the active ingredient include RejeX-it®, Bird Shield®, Goose Chase™, and Fruitshield.
Anthriquinone acts as both a taste aversion agent and a visual deterrent. Vegetation treated with anthriquinone changes color within the ultraviolet portion of the spectrum (birds can detect ultraviolet colors). This color change alerts Canada geese that this vegetation is unpalatable, and they will avoid it. Anthriquinone is the active ingredient in the product Flight Control®, and it is considered non-toxic when applied in accordance with the manufacturer's guidelines. www.flightcontrol.com
Wouldn’t it be awesome if spraying a repellant on turfgrass areas actually helped!