Why not shoot the geese? The article didn't say that they were protected, endangered, or otherwise not-shootable. Is the section of Ottaway the geese are polluting not safe for discharging firearms?
In New Mexico, we have a number of animals that require culling (due to the elimination of top level predators) and the way New Mexico Game and Fish solves the problem is by issuing hunting licenses. This seems to work pretty well for us.
Bloody good question, as a resident of the Ottawa area I can testify that there doesn't exactly seem to be a shortage of geese, and in some places they really are a nuisance.
So I did a little digging, sure enough our efficient government have created a Canada Goose FAQ. And it turns out that the little buggers are protected under the Migratory Birds Convention Act because their migratory. However:
The Act gives the federal government the responsibility to establish hunting seasons, and Canada Geese are greatly appreciated by migratory game bird hunters across the country. More than 500 000 Canada Geese are taken in Canada each year by hunters.
Migratory Birds Hunting Regulations, 2013–2014: Ontario
There is an open season on the Canada Goose from the beginning of September to the middle of December. But with a limit of 5 geese per licenced hunter per day.
So yes, hunting geese is an option, but no, just shooting them in the spring would be illegal.
TL;DR -- It's the nesting season, their migratory and there's international agreements covering the treatment of migratory birds, we can only hunt/shoot them in the fall.