There used to be a mink farm here that had problems with seagulls, either the mink carcasses or the food I don't know, but there were literally tens of thousands of seagulls infesting that 10 acre farm yard. it was close to town, actually in the city limits i think, and the birds were a nuisance to the farm and also the entire city of Wetaskiwin.
The farm owners used to get a 1-day permit to shoot nuisance seagulls. 20-30 shotgunners would descend and all hell would break loose for half an hour or so and there would be hardly any seagulls around for another year.
That was 30-40 years ago. Times have changed.