Predation has long been a biological taboo, the meme being that the "last wolf will not eat the last deer" etc. This is a legacy left by Lorenz, starting first with aggression, and then spreading to other concepts. Over the years biologists have realised that predation does play a role, often a major role, in the wildlife mix. This is especially true with predators that have alternative food sources, ie corvids, gulls and rats that also feed on garbage and have plenty of energy to indulge in what is apparently hobby predation. Such predators are not limited by their prey.
And predators can and do cause the extinction of their prey, and prey rebounds when predation is removed, as proven by management projects as in Rat Island and Campbell Island.
It took biologists a generation to overcome Lorenz's influence on aggression. Wonder how long it will take to correct the predator myth.
Delta Waterfowl has done some very interesting research on the effects of predation and most especially predator control on duck populations in the Prairie Pothole region, one of the most significant breeding grounds for waterfowl in all of North America.
Suffice it to say that it appears to be perhaps the single most important factor regarding population levels. Ducks are pretty adaptable to different habitats if they are alive. But when killed by predators, they don't have much chance to adapt to any type of habitat.
