English Cocker Spaniels, like many breeds that originated as working dogs, have some genetic lines that focus on working-dog skills and others that focus on ensuring that the dog's appearance conforms to a breed standard. These are referred to as the "working", or "field-bred", and "show dog" strains.
Show Bred Cockers
After World War II, the show-bred Cocker Spaniel increased enormously in popular appeal and, for a while, was the most numerous Kennel Club registered breed. This popularity increased the view that all Cockers were useless as working dogs. However, for many dogs this is untrue, as even some show-bred Cockers have retained their working instinct.
Today, this breed is experiencing a resurgence in usage as a working and hunting dog. Dogs from working lines are noticeably distinct in appearance. As is the case with the English Springer Spaniel, the working type has been bred exclusively to perform in the field as a hunting companion. Their coat is shorter and ears less pendulous than the show-bred type. Although registered as the same breed, the two strains have diverged significantly enough that they are rarely crossed.