"Separating Ross's and Snow Geese (so-called “white” geese in the Genus Chen) can sometimes cause problems for those who aren't used to seeing these two beauties!"
Separating Ross's and Snow Geese (so-called “white” geese in the Genus Chen) can sometimes cause problems for those who aren't used to seeing these two beauties! Both of these geese are high arctic breeders with booming populations. They migrate throughout the United States and winter in the southern regions of the country, sometimes delighting our friends across the pond as vagrants to Europe. Away from the US Southwest and Gulf Coast wintering strongholds of Ross’s Geese we find flocks of primarily Snow Geese with the occasional Ross's mixed in, growing rarer to the east.
Part of the challenge with Chen geese is their variability. Snow Geese are the larger of the sister species but note that there are lesser Snow Geese that approach the diminutive Ross's in size. Both of these species come in light and dark morphs known as “Blue Geese”, although dark Ross’s Geese are exceedingly rare. Some Blue Geese are "bluer" than others (they have more extensive dark feathering on their bodies) and juvenile Blues can look nearly all black while juvenile light-morph birds look dirty light gray. With the variability in coloration it becomes important to focus primarily on size and structure to separate these birds.
When seen together, separation of the two can be fairly self-explanatory. Notice the four birds in the photo below. Can you see the size and shape differences here? There are two Snow Geese (one a dark-morph) and two Ross’s Geese in this photo! The Ross's Geese (top and second from the bottom) are smaller versions of the Snow Geese, sporting much stubbier bills with little or no "grin patch" and a shorter neck. The culmen (top of bill) is nearly straight on the Ross’s Geese while the Snow Geese display gently dished culmens. Ross’s heads look more rounded, and between that and the shorter bill one might call them "cuter." Not as cute are the bluish warty bumps (caruncles) that mature male Ross’s develop at the base of their bill. Snow Geese have a much larger bill with a noticeable dark grin patch (combed black where the upper and lower halves of the bill meet (above and below the tomia, or inner cutting edges of the bill), a flatter looking head, and a proportionately longer neck. If you can see black in the center of the bill from any distance, particularly from afar, then you are looking at a Snow Goose. Two more comparison pics follow, the first of a Ross’s Goose and the second of a Snow Goose.
Even at a distance, note the structural differences between the Ross’s Goose (trailing) and the Snow Goose (leading) in the following picture:
The above shot was taken at Bosque Del Apache National Wildlife Refuge last November. While the Sandhill Cranes get a lot of the spotlight at Bosque del Apache, the geese also provide spectacular sights, comparison studies, and photo opportunities at the refuge. In a welcome turn from the hordes of sky carp found in much of the US, white-cheeked geese (Canada & Cackling) are kind of scarce there. But so-called "white" geese are present in force and typically show well. For some reason, the Farm Loop on the refuge didn't have corn planted last year so the goose situation had changed from previous years. It was tough to get the massive "blast off" shots that happened on the northern part of the refuge when a coyote or eagle spooked 4 or 5-digit goose flocks, but there were still plenty of chances to study and photograph almost all of the Chen flavors (still haven't seen the elusive dark-morph Ross's Goose