Canada geese have become a common sight
—by Steve Lekwa
Canada geese have become such common nesting birds in our area that many folks probably don’t pay them much attention any more unless it’s to complain about them when they foul our beaches, golf courses, and even yards with their droppings. It wasn’t always so. There were no nesting Canada geese in Iowa when I was growing up, and the sound of a migrating flock was enough to make me run outside just for the thrill of seeing them. The sound and sight of migrating geese stirred my soul then, and thankfully still does today even though I’m well aware of some of the problems caused by our local nesters.
While almost everyone can identify a Canada goose as different from other wild geese, only a few concern themselves with trying to identify the various subspecies or races within the species. Canada geese (Branta canadensis) in their various forms nest all across North America from Alaska’s Aleutian Islands and the high Arctic to Labrador and south into all but the southernmost states. The Birds of North America listed 11 subspecies of Canada geese in their 2002 edition. They range from our local giant race (Branta canadensis maxima) that can tip the scales at more than 20 pounds to the smallest, split out with separate species status as Cackling geese (Branta hutchinsii) in 2004 by the American Ornithologist’s Union. Cackling geese have four regional subspecies with the smallest of all being the western Branta hutchinsii minima that’s barely larger than a Mallard duck at only three to four pounds.
Differences in regional nesting preference are another way to separate the various populations. This, alone, may be enough to explain some of the genetic differences in the various races. Giants nest the farthest south and Cackling geese nest the farthest north. One race nests around Hudson Bay and another across the central Canadian prairies. The ranges overlap, though, and where they do the birds interbreed, showing characteristics of both parent races.
The various races or subspecies do show generalized differences in coloration, size, shape, and tone of voice, but the variations can be small. Western races tend to be darker than eastern ones. Northern races tend to be smaller than southern ones. Smaller ones tend to have higher pitched voices than larger ones. Sharp identification lines are blurred, however, by color and size variation within each group, between larger males and smaller females, and between larger old birds and smaller young ones. The smaller races of Canada geese were split out as Cackling geese due largely to genetic differences that appeared to set them apart as a separate species rather than subtle differences we can see and hear.
For our purposes here in Iowa, Canada geese can be sorted into three groups. The big ones are our local Giant Canada geese. They nest here, but most of them migrate a short distance to the south for at least a month or two in the winter. The smallest and most wary ones are Cackling geese that nest across Arctic Canada and begin appearing in our area about now. They’re small enough to appear distinctly different and tend to stay together in mixed flocks. In the middle are the bulk of the birds we’ll see here in wintering flocks. They migrate from nesting areas around Hudson Bay and westward into the Canadian prairies. They’re sometimes referred to as Lesser Canada geese or the Eastern Prairie flock. All three races, or maybe it’s two subspecies of Canada geese and Cackling geese, will be around until colder weather drives our local giants farther south. See if you can see the three different sizes as more birds arrive in our area. Don’t worry if you can’t sort them out, though. In the words of David Sibley, one of the nation’s leading experts, all identification (of Canada geese) should be approached with a healthy dose of skepticism. Just enjoy and hopefully be at least a little inspired by them while they’re here.