Cackling geese with a Canada goose

From the U.S. Fish and Wildlife Service Midwest Region:

The newly recognized cackling goose is a smaller version of the Canada goose. Formerly considered the smallest subspecies of one variable species, recent work on genetic differences found the four smallest forms to be very different.

Photo: Cackling geese with a Canada goose by Len Blumin/Creative Commons. https://flic.kr/p/iooo8b