Diminutive cackling geese are occasionally seen with much larger Canada geese. Photo by Dominic Sherony / Creative Commons.
The Canada geese now honking overhead in V-formation, perhaps more than any other birds, exemplify the fall migration. Except when they’re not really migrating, and except when they’re not really Canada geese. One of the most familiar birds on the continent fractures our notions of predictability and uniformity among wildlife.
Yes, historically these geese were in large part Canadian, breeding throughout the low Arctic from the Aleutians to Newfoundland and south into the northern United States. Across that range, Canada geese exhibited a high degree of philopatry – the tendency of an animal to stay in or return to its place of origin. Over the course of their evolution, though, these geese split into somewhat distinct breeding populations. As a result, biologists and birders recognized 11 subspecies, varying mostly by size – smaller to the north and west, and larger to the south.
The largest goose in the world, for example, is the “giant” Canada goose (Branta canadensis maxima), and one of the smallest – not much bigger than a mallard – is a subspecies known as “minima.” This range of body sizes would be similar to one race of humans standing six feet tall and another race barely three-and-a-half feet tall.
This unusual variation in size – perhaps the most extreme among all birds – set the stage for a redefinition of what it means to be a Canada goose. In 2004, the American Ornithologists’ Union split the bird known as the Canada goose into two species. The four smallest groups – and for the most part the darkest, including the tiny minima – are now called the cackling goose (Branta hutchinsii), and the seven other subspecies remain Canada goose.
Most of the cackling geese (birders affectionately call them “cacklers”) migrate south through central Canada and winter in the central U.S. But strays occasionally show up in the eastern part of the country, which means that those diminutive, stubby-billed geese you might find among the bigger geese are not actually Canada geese – at least, not anymore.
But more than changing the way we name this goose, humans also altered its distribution and migration patterns. By the end of the nineteenth century, overhunting, egg collection, and the destruction of wetlands depleted Canada goose populations, particularly in the southern portion of the bird’s range. In the 1930s, federal and local wildlife managers responded by relocating and reestablishing maxima in the U.S., in part to please hunters.
The restoration went a bit viral. Canada geese, ruthless opportunists, are among the few birds able to digest lawns, which began to proliferate with the mid-century spread of suburbia. Feeding and nesting in parks, golf courses, farms, and airports – especially those near lakes and small ponds – the giants pushed southward beyond the Canada goose’s historic range. A semicolonial breeder to the north, the Canada goose can also nest alone. It now breeds in every state.
In many of these new frontiers, Canada geese have lost their need (or will) to migrate and have become year-round residents in places where previously geese only came to visit for winter. And in some locations, Canada geese have become a nuisance, particularly in small ponds, in neighborhoods, and at airports.
The Canada goose now exhibits a variety of races and behaviors. The migratory geese breed in northern North America and winter as far south as Mexico, and resident birds live across the United States year-round or don’t migrate very far. A “mixing of the races” has also blurred some of the genetic and behavioral distinctions between related species. These lines have always been a bit fuzzy; human relocation and manipulation has made them even more so.
So have another look at those geese overhead. They may not be heading south for winter, and a few of the noticeably smaller ones might not even be Canada geese. One of the most iconic symbols of autumn turns out to be iconoclastic.
Bryan Pfeiffer is an author, wildlife photographer, guide, and consulting naturalist who specializes in birds and insects. He lives in Montpelier, Vermont.