Are a very large bird, and are slightly larger than a mallard. These birds nest extensively out west on the Canadian prairies, and in most northerly sections of most Canadian Provinces. 

Their numbers were in decline over the past few years, owing mostly to several dry years, as well as loss of habitat. Lately though, they've rebounded with encouraging population growth, thanks IN PART (ONLY) to lower bag limits as a needed and successful conservation measure. The recent wetter breeding years and better breeding conditions have played a more important role in the (recent) growing canvasback numbers. Too, and hopefully(optimistically) the canvasback is becoming more adaptable to person made wetlands and staging areas, and that populations continue to grow. 

The canvasback is primarily a solitary bird though, and doesn't like people's activities much, especially in breeding seasons. As well, they like larger waterbodies to nest near, and can't just nest in any small pothole like many 'puddle' ducks can. 

They are divers, and eat a lot of insect/animal life during the spring/summer season; though, they primarily eat vegetation such as water celery, coontail and other such aquatic life, and eat this vegetable matter when a choice exists. Canvasbacks are truly awesome table fare. 

Once they start to migrate, you'll find them on 'big waters' and stage up most often with several family units; they don't usually cluster up in 'rafts' of more than about fifty to a hundred birds. 

In the Long Point area, where I hunt extensively, one may find them rafted up in much larger groups, several acres in size, usually just before they 'pull out' to go south, often being 'frozen out'. Canvasbacks are a very hardy bird, most often having to be 'pushed' south by bad/cold/stormy/snowy/sleet/freeze-up weather. 

A person has to be a rugged individual to be able to withstand the savagery of the elements needed to have consistent canvasback shooting. Most hunters regard this as the epitome of waterfowling though, especially when hunting from 'layout' boats in these bird's 'big water' haunts!