At this time of year, birders keep a watchful eye for Ross's Geese. What many don't know is that there can be hybrids with Lesser Snow Geese that may look similar to a Ross's Goose but are usually distinct enough that informed observers can at least raise a caution flag.
First, the odds of finding pure Ross's Geese seems to be higher the further west we go in the province. That makes it easier because most of the birds observed in Central, the Southwest and the North seem to be just Ross's Geese. The further east you go the greater the possibility of seeing a hybrid rather than a pure Ross's Goose, at least from my experience. I tend to think some years up to 1/4 could be hybrids there which means careful observation of field marks is necessary. I have never seen a bird that suggested breeding between a Ross's Goose and Greater Snow Goose however. There is no clear cut hybrid. They are always a blend of features but the first alert should come with size. Almost all hybrids are larger than Ross's because the Lesser Snow Goose is noticeably larger and its genes tend to dominate. Of course size is relative when you don't have a direct comparison with a pure Ross's Goose but you can usually compare directly with Canada Geese. It's like an inexperienced birder telling the difference between a Downy and a Hairy Woodpecker. A hybrid tends to not look significantly smaller than a Canada Goose, closer to what you'd expect a Lesser Snow Goose to be. A true Ross's Goose is much smaller than a Canada, more like a Mallard by size. The next feature to check is the head. Go right for the bill first. It is stubbier than a Snow Goose and should lack a grin patch. However, some hybrids have a reduced grin patch that can be difficult to see at a distance. The base of the bill should appear straight in a Ross's Goose not slightly concave, a feature of a Snow Goose, hence a better chance of being a hybrid in that case. Ross's Goose has caruncles at the base and Snows do not but if the hybrid has enough Ross's features this one can present. Also, if the neck appears longer than it should and the bird is not obviously stretching you can probably say hybrid. In many cases it is the head that gives the biggest suggestion of being a Ross's Goose and since we tend to focus attention there it can tip the balance in favour of that feature, missing the other field marks. I have seen a hybrid that had a Ross's head but characteristics of Lesser Snow Goose for the neck and body. There are no clear-cut field marks so you can have a really obvious bird that touches most of these points for a Ross's Goose and others that are questionable. Always check with this possibility in mind so misidentification is minimized. Brian Morin -- Ontbirds and Birdnews are moderated email Listservs provided by the Ontario Field Ornithologists (OFO) as a service to all birders in Ontario. Birdnews is reserved for announcements, location summaries, first of year reports, etc. To post a message on Birdnews, send an email to: [email protected]. If you have any questions or concerns, contact the Birdnews Moderators by email at [email protected]. Please review posting rules and guidelines at http://ofo.ca/site/content/listserv-guidelines To find out more about OFO, please visit our website at ofo.ca or Facebook page at https://www.facebook.com/OntarioFieldOrnithologists.
