Date: 1/1/18 6:52 am
From: 'Steven Mlodinow' via Colorado Birds <cobirds...>
Subject: [cobirds] What happened to Lesser Canada Goose (parvipes)?
Greetings All

I've been asked this question enough, that I decided to post a bit about it and related goose issues

1- Lesser Canada Goose (Bc parvipes) is a conglomeration of small Canada Goose populations rather than a true subspecies, in the evolutionary sense.
2- Partly because of 1, parvipes has a broad range of appearances, varying from very close to Richardson's Cackling Goose and Taverner's Cackling Goose all the way to appearing essentially just like Bc interior (which has been subsumed into Bc canadensis, which is what I will call it from here on). Since there is a continuum from Bc canadensis thru parvipes, drawing a meaningful line between the two is not possible.
3- Because of #1 and #2 above, continuing to have parvipes as a separate entity in eBird makes little sense.

Related to all of this:
1- Leafloor et al found, and proved genetically, a rather large hybrid zone between Bc canadensis and Bh hutchinsii (Richys) on the west side of Hudson Bay. This hybrid zone seems of long duration and stable, but produces hybrids that can look like either parent or anything in between, including birds that look somewhat like "parvipes."
2- Since small Canada Geese breed side by side with Cacklers (Bh taverneri) on the north slope of Alaska (and probably Yukon), it would be very surprising if a hybrid zone did not exist at those locations as well.
3- The border between the breeding ranges what we call Taverner's Cackling Goose and Richardson's is unknown. My observations in e. CO would suggest that there is a large intergrade zone, as I see many intermediate birds. Indeed, I would suggest "lumping" Taverner's and Richardson's (the only sticky part of this involves the geographically separated w. AK population of Taverner's, which migrates down the west coast and not into the interior).

I see flocks of birds that look like absolutely pure Richardson's. Then I see flocks that are a mishmash of everything from "Lesser Canada" to Richy to Tav, with most bird of intermediate appearance.

The top 3 points will help explain some of the thinking that went into eBird taking parvipes and placing it with canadensis. The bottom 3 points serve as a caution re: the identification of Taverner's, Richardson's, and "Lesser" Canada Geese.

Happy New Year
Steve Mlodinow

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