By Bruce Batt, Ph.D.
Waterfowl managers recognize 19 different populations of Canada geese. One of these, the cackling Canada goose, breeds in one small part of the vast western Alaska landscape and nowhere else in the world.
Weighing only about three pounds, the cackling Canada is just a little bigger than a mallard and has a distinctive short neck, usually with a white neck ring. Its call is a brief, high-pitched unc.
Canada geese of the Atlantic Flyway population nest in northern Quebec. Weighing around eight pounds, they have the more typical look of Canada geese-large bodies, long necks, and light-colored breasts. Their call, a resonant uh-whonk, is longer and lower pitched than that of cacklers.
In southern Manitoba, the giant Canada goose weighs 12 to 14 pounds, a whopper compared to most other populations of Canadas, and it has the lowest-pitched and most prolonged call of any of the Canada geese. This is the goose many of us typically see in city parks and on municipal golf courses.
Each of these three populations is distinguished by size, plumage, and even by their calls. We would see additional diversity if we looked at the other 16 Canada goose populations throughout the continent. But the ducks are different-or should I say, not different.
Mallards in western Alaska look the same as mallards nesting in Saskatchewan, New York, Wisconsin, or northern California. You cannot tell where on the continent a mallard may have hatched (with certain exceptions; see It's a Deep Gene Pool on page 30), as you could with Canada geese, by looking at color variation or weight differences.
The same is true for most other species of ducks, except for some of the sea ducks, specifically eiders and harlequins.
So, why do we have so many races of Canada geese and no clearly identifiable races of most ducks? The answer lies in several behavioral patterns that are quite different between the two groups.
The most important difference is explained by the differences in the family structures of geese and ducks. Geese form long-term pair bonds. The male and female generally stay together as long as both are alive, but will form new pairs if one mate dies. The pair cooperates in everything related to family maintenance. The male defends the female while she incubates.
He defends her and the family after they hatch, and both male and female tend the family throughout their first year of life. Adult geese show their young where to stop and feed during migration, where to spend the winter, and how to return to the breeding grounds.
In fact, all the families and nonbreeding geese from a given breeding region will usually migrate together, stopping at traditional staging areas and returning north through those same stopping places. This is a sort of super-extended family.
Even when goose families are broken up because of the death of a parent or a sibling, orphaned or widowed birds still associate with other Canada geese from the same breeding population.
In the spring, or later in the year, young birds that have never been paired before, as well as widows or widowers, will seek mates among the other Canada geese with which they associate.
It is highly likely that they will pair with a bird from the same breeding population.
That is, even though the odds are against pairing with a sibling, a parent, or an aunt or uncle, it is highly likely that an individual goose will pair with a bird from the same general area where it was hatched.
Pairing with a not-too-distant relative isn't out of the question. There is a mathematical likelihood that some measure of inbreeding does occur.