The reality is that giant Canada geese are naturally larger than other subspecies. Their large body size and distribution in temperate regions also explain why giant Canada geese do not migrate
predictably, if at all. Instead, they hang around until extreme cold and deep snow force them to move south. Thus giant Canada geese haven't lost their migratory instincts as some believe; they never had them to begin with.
Today giant Canada geese can be found throughout their former range and in every U.S. state. Their numbers have increased exponentially in recent decades, and they now rival or outnumber migratory Canada geese in each of the flyways. Current estimates suggest that there are nearly 4 million giant Canada geese in North America: 1 million in the Atlantic Flyway, 1.7 million in the Mississippi Flyway, and slightly over 1 million in the Central and Pacific flyways
Why have giant Canada geese been so successful? In general, Canada geese are long-lived birds with relatively high survival and low reproductive rates. However, larger-bodied subspecies have higher survival and reproductive rates than their smaller cousins. Giant Canada geese begin nesting
at a younger age, have larger clutches, and can defend themselves and their nests from most predators. Unlike their migratory counterparts—which nest in the Arctic and subarctic, where inclement weather often limits breeding success—giant Canada geese nest in temperate regions, where the weather is more favorable and the breeding season is longer. This gives the birds time to renest if their initial nesting attempts are unsuccessful.
Giant Canada geese have also benefited from manmade changes to their environment. Canada geese are grazers by trade and prefer the succulent new growth of grasses and sedges, which explains why these birds are so fond of manicured lawns, parks, and golf courses. But Canada geese also grub for roots and tubers and feed on various seeds and waste cereal grains.
Their adaptable feeding habits and tolerance for people have enabled giant Canada geese to exploit urban and agricultural landscapes alike. In short, people have created ideal living conditions for these birds.