Depending on your location, year-round populations of Canada geese in the United States may be “expansion teams” that have relatively recently become established in areas far south of their original territories, losing their migratory habits.

The largest representatives of the Canada goose, Branta canadensis maxima, almost became extinct in the early part of the 20th century. Efforts to re-establish the species succeeded beyond expectations, sometimes leading to overpopulation, according to the Birds of North America Online, a reference work published by the Cornell Lab of Ornithology. The overflow from newly overcrowded areas has resulted in a southward expansion of the normal breeding range, with year-round residency.

Normally, Canada geese fly back to nest where they were hatched in the northern reaches of Canada. But these newer populations have no such childhood memories. The Canadian government says geese that still breed in the traditional sub-Arctic areas of Canada continue to migrate south to the relatively balmy United States in the winter, mingling with year-round residents.

To confuse matters further, some migratory Canada geese do not travel as far south in the winter as they used to, the Cornell Lab of Ornithology reports.

These birds have benefited from changes in weather, hunting patterns and agricultural practices that leave more waste grain behind for winter foraging. 

(https://www.nytimes.com/2015/10/06/science/some-canada-geese-are-losing-migratory-instincts.html)

(Cannot write Chinese with this computer, so copy this article)