Monday, November 23, 2009

At the pond... Canada Goose

Canada GooseWestern Canada Goose, Hillsboro, Oregon on 6 December 2008 by Greg Gillson.


Everyone knows the Canada Goose. Everyone except birders, that is. Why do I say this?

Birds of Oregon: a general reference (2003, Marshall, Hunter, and Contreras, editors) lists 8 subspecies of Canada Goose found in Oregon. Some birders attempt to identify these field identifiable subspecies, or races, when they can. Other birders, however, pay no attention to subspecies, as they can't count them as a separate species on their life list. And, well, many birds are just really hard (or impossible) to pin down to a subspecific identification. So why bother?

Well, surprise! The American Ornithologists Union (A.O.U.) recently "split" the Canada Goose into two separate species. The larger birds, some almost the size of swans, are still called Canada Goose, Branta canadensis, while the smaller geese, some the size of city park ducks, are now called Cackling Goose, Branta hutchinsii.

While your friend who knows next to nothing about birds confidently identifies the overhead skein of birds as "Canadian" Geese, you're not so sure anymore.

Cackling Geese cackle, of course, while Canada Geese honk. That's just a sweeping generality, as there seem to be several "tweener" populations that are very difficult to tell apart. In general, Cackling Geese have short necks, stubby little bills, and wing tips that extend well past the tail at rest.

The resident Canada Geese, the ones in city parks and wetlands that lead goslings around in April, are the Western Canada Geese. They are very large, have white breasts and long necks and bills. The bird in the photo above is a Western Canada Goose.

In winter, we are visited by the smaller, white-breasted, Lesser Canada Goose from the north. These are more common east of the Cascades than west.

And, in the Willamette Valley of western Oregon winters a dark breasted Dusky Canada Goose. The Vancouver Canada Goose is very similar. Some of these winter along the coast, as far south as the Nestucca National Wildlife Refuge near Pacific City, Oregon.

The Giant Canada Goose is a bird of the Great Plains that has been introduced widely in North America. There is an introduced resident population on the Lower Columbia River near Astoria, Oregon. Many of these released birds bred with the abundant local resident Western Canada Geese so that most birds here and elsewhere in the Pacific NW showing "Giant" field marks (white foreheads and larger than the Western race) are probably not pure.

I'll write again about the Cackling Goose later this winter. The main identification challenge is separating the Lesser Canada Goose from the Taverner's Cackling Goose. A good article on this is John Rakestraw's blog on the Lesser Canada Goose.