Honestly there aren't that many species of ducks in Ontario. Heres 26 the species of ducks you'll find in Ontario, the bold ones are common that you should probably know. Cut that list in half if you only hunt puddle ducks. Most field guides I've seen don't show the wings which are one of the best ways to ID them.
Wood Duck, Aix sponsa
Gadwall, Anas strepera
American Wigeon, Anas americana
American Black Duck, Anas rubripes
Mallard, Anas fulvigula
Blue-winged Teal, Anas discors
Cinnamon Teal, Anas cyanoptera
Northern Shoveler, Anas clypeata
Northern Pintail, Anas bahamensis
Green-winged Teal, Anas crecca
Canvasback, Aythya valisineria
Redhead, Aythya americana
Ring-necked Duck, Aythya collaris
Greater Scaup, Aythya marila
Lesser Scaup, Aythya affinis
Harlequin Duck, Histrionicus histrionicus
Surf Scoter, Melanitta perspicillata
White-winged Scoter, Melanitta fusca
Black Scoter, Melanitta americana
Long-tailed Duck, Clangula hyemalis
Bufflehead, Bucephala albeola
Common Goldeneye, Bucephala clangula
Barrow's Goldeneye, Bucephala islandica
Hooded Merganser, Lophodytes cucullatus
Common Merganser, Mergus merganser
Red-breasted Merganser, Mergus serrator
Ruddy Duck, Oxyura jamaicensis
And honestly you should be able to ID them before you even shoot them, or at least have a very good idea of what it could be.