Appreciating Rice Wildlife: Snow and Ross’s Geese
By Luke Matthews
White geese are the most abundant migratory goose species in California, with large concentrations of birds on the refuges and rice fields of the Sacramento Valley. The term ‘white geese’ or ‘light geese’ refers to two distinct goose species, Snow Geese and Ross’s Geese.
These two species look fairly similar as they are both pure white geese with black wing tips and pink legs. There is also a second color morph known as blue morph, although it is far less common in Ross’s. Geese with this color morph have grayish-blue bodies with white heads. Blue morphs are not very common in California but become more common across the eastern flyways, with high proportions of ‘blues’ in the mid-continent populations.
While Snow and Ross’ Geese have a lot of similarities, there are a few key ways to differentiate them. The best way to learn to tell them apart is to compare photos of each species side-by-side and analyze the differences. Here are a few helpful tips: Ross’s Geese are about two thirds the size of Snows; additionally Ross’ have much stubbier bills and lack the “grin patch”. In contrast, Snows have a longer bill with a “grin patch”, a distinct black oval on the upper and lower portions of their bills.
Ross’ and Snow Geese both breed in large colonies. In many cases Ross’s will nest in mixed colonies with Snow Geese. Their breeding grounds extend from as far south as the Hudson Bay, north onto the Tundra and west across Northern Alaska. Snow Geese also have a nest on Wrangle Island in Russia; in fact, many of California’s wintering Snow Geese breed on Wrangle. Based on the most recent counts and estimates there are roughly 12-13 million Snow Geese and 500,000 Ross’ Geese that winter across North America. The vast majority of these birds winter in the mid-continent, but approximately 1.2 million of them migrate to the Central Valley of California, with a majority of those being Snow Geese.
Luke Matthews is the Wildlife Programs Manager for the California Rice Commission