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Resident maximas and migrating interiors

All geese are not created equal. Those wreaking the most havoc in Toronto are the largest subspecies of Canada goose — the giant Canada goose (Branta canadensis maxima). They are also known as resident geese since they breed and nest locally. When Toronto freezes over, some migrate to the slightly warmer American side of Lake Ontario or outside city limits where harvest leftovers lie in fields. After the spring thaw, many resident geese that are old enough to fly but too young to breed as well as some failed breeders — all known as moult migrants — head to James Bay for the summer.

There is only one recognized species of Canada goose, but there are enough differences among North American populations that biologists distinguish anywhere from 11 to 188 subspecies — an issue “scientists have argued about for 50 years,” says Jim Leafloor, a waterfowl biologist with the Ontario Ministry of Natural Resources in Cochrane, Ont.

“The birds encounter different environments depending on where they were raised,” says Leafloor. “They adapt to local environments and thus look different.” In general, he says, Canada geese are largest in southern populations and become progressively smaller in northern populations.

Some conservation biologists agree that hunting is the most effective way to decrease overabundant wildlife populations, so some regions are changing the timing of their hunt to coincide with the movements of giant Canadas. In Ohio and Michigan, for example, bag limits for Canada geese were raised early in the hunting season to target giant Canadas, and early goose seasons have been established in southern Ontario for the same reason.

Some migrant populations, such as the slightly smaller subspecies B. canadensis interior, are decreasing since they face growing competition in their summer nesting range along southern James Bay. Already scarce food resources are being depleted by unprecedented snow goose populations (Anser caerulescens) and, to a lesser degree, by giant Canada goose moult migrants. Increased hunting of northern birds may further diminish migrant geese in central North America. But many people wonder whether we should care. There seem to be enough Canada geese around that their survival as a species is far from threatened.

Leafloor says it is important to conserve subspecies since greater variety can help the long-term survival of the species as a whole. "Diversity is good since more diverse populations can withstand catastrophic events."

Elizabeth Shilts

Modified from original by Steven Fick/Canadian Geographic

A. Southern James Bay geese: Migrants wintering in the United States move north via the Mississippi and Atlantic flyways bound for summer nesting grounds around James Bay.

B. Toronto moult migrants: Some Toronto-area geese move to James Bay for summer moulting.

C. ’Residents’: Toronto-area breeders occasionally leave the city for rural Ontario, or to overwinter in the U.S.

D. U.S. moult migrants: Some geese from the northeastern U.S. migrate to southern Ontario for summer moulting.

(This article first appeared in Canadian Geographic magazine, May/June 1998. It may not be reproduced without written permission from Canadian Geographic.)


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