Prothonotary Warbler

Prothonotary Warbler

Monday, 23 November 2015

Ross's Goose, not a hybrid

Today I was at Rondeau hoping to locate the Summer Tanager that had been seen the previous couple of days. Check out Blake Mann's blog if you haven't already seen it.

I couldn't make it to Rondeau yesterday, so today was the day, I was hoping....But in spite of several hours of searching both where it had been seen the last two days as well as just as likely spots elsewhere along the cottage community, I was not able to find it. It may still be there, or the relatively clear night last night and the colder temperatures may have been enough impetus for the lingering bird to decide enough was enough, and it was time to leave.

Giving up on the tanager, I stopped to check the lake front area at the traffic circle at the north end of the park to see what was in the relatively sheltered waterfront. I immediately noticed two small white geese mixed in with several hundred Canada Geese that have been occupying this part of the park which is off limits to hunters. I first thought 'Snow Goose' but then quickly realized that the combination of the short stubby bill, the bluish-purple base of the bill, the lack of a grin patch and the fairly straight, not sloping, feathers from the top of the bill to the bottom, all signalled Ross's Goose!

Note first the size comparison with one of the typical Canada Geese.

Next note the other features of the base of the bill as described above.
It looks pretty convincing to me. But Ross's Geese are known to hybridize with Snow Geese, and if they do, the characteristics aren't so clear. Note these next two images of the small mostly white goose which was associating with Tundra Swans. I took these photos last year near St. Clair National Wildlife Area, fairly late in the day, so the images aren't quite as sharp as the ones I took today.

The bird in question is small, no doubt about that. But the beak is not as short and stubby as the ones I saw today. It does lack the grin patch, and it has a fairly straight slope to the base of the bill. The bluish-purple area at the base of the bill isn't very obvious. So some goose biologists familiar with northern geese advised me that this bird probably has some Snow Goose genes in its makeup, and would more likely be considered a hybrid. Interestingly another goose biologist suggested that it was a good example of a Ross's Goose, and yet another excellent birder indicated it was more likely a good example of a Snow Goose! So even the experts gave different opinions. Admittedly to be completely fair, it is hard to be definitive when only seeing a single photo, not watching the bird from different angles and picking up subtle nuances of the way it appears in real life. And when a bird shows some characteristics of a species or a hybrid, but not all, it adds to the challenge.

So I learned from the experience of last year, and I consider myself a bit more careful in calling out 'Ross's Goose' when I see something that appears to be one. And in that vein, I am fairly confident that the birds of today are good examples of pure Ross's Goose.







No comments:

Post a Comment