These particular birds are hybrids, very popular with exhibitors but generally not well-known outside show circles. Canary mules have won the coveted best-in-show award at the National Exhibition of Cage and Aviary Birds in the UK more times than any other type of bird, including the budgerigar, although they are not well-known outside bird-keeping circles.

Mules are the result of crossing a cock finch with a hen canary. A wide variety of aviary-bred finches, such as goldfinches, bullfinches and greenfinches may be used in pairings of this type. The resulting hybrids generally show the characteristics of both parents - the vivid reddish coloration of the bullfinch (see left) for example, combined with the singing prowess of a canary, in the case of a bullfinch mule. Their unique appearance contributes to their appeal.

Although long-lived, mules are invariably sterile, and so cannot breed themselves. These birds are easy to keep on a good canary seed mixture however, along with green food such as chickweed. They can become quite tame when kept as household pets, and make lively aviary occupants.It is obviously important to encourage both birds to come into breeding condition at the same time, so that mating can be successful.

Certain crosses are much harder to achieve than others, with the result that some mules are much rarer than others. It is normal to use fairly stocky breeds of canary such as the Norwich Fancy in pairings of this type, because they make good mothers.