I just spent some time researching this issue, and it's indeed a bit complicated. It appears that the two western subspecies of the respective species (Tundra and Taiga) are pretty clear-cut: the classic Tundra ( *rossicus*) is a relatively small, rather short- and thick-necked bird with a short and thick, triangular bill. The western Taiga subspecies *fabalis *is much larger, with a long, thin, almost swan-like neck and a much longer and thinner bill that usually has orange on much of its length, while *rossicus *has a small orange or pinkish patch near the tip of the bill (in fact, I never had much trouble assigning a bean goose to one of the two species back in Germany, where both of the western subspecies overwinter).
The two eastern subspecies (Tundra *serrirostris *and Taiga *middendorffii*), which are by far more likely to make it to the western US, are a different story. They tend to be a little more similar to each other - *serrirostris *is bigger than *rossicus *and on average has a slightly larger bill, making it a bit harder to tell it apart from a *middendorffii *Taiga Bean-Goose. Also, *middendorffii *appears to regularly show a bill pattern that has a lot less orange, much more similar to a Tundra Bean-Goose.
A much-discussed bird with characters intermediate between the two eastern subspecies showed up at Salton Sea, California, in Nov 2010. I'm adding the link to this very interesting and informative discussion:
Comparing photos of the Finley goose (Doug Robinson posted some nice close-up head shots on eBird) to many online photos, I believe that our bird still looks good for an eastern Tundra-type. It doesn't look massively larger compared to the Cacklers around it - I believe a Taiga Bean-Goose would stand out even more. Its head looks pretty rounded in most photos, with a rather steep forehead, and the bill, albeit somewhat on the longish side, still looks shorter than I would expect in a Taiga goose (which usually shows a more sloped, swan-like profile). Also, the bill seems to have a rather thick base, and the lower mandible shows a slight droop at the center, typical for Tundra Goose (Taiga has a much straighter lower mandible). The neck of the Finley bird looks pretty short and thick to me, another thing that points toward Tundra. Compared to the ambiguous California bird, the Finley goose looks a lot shorter- and thicker-billed, placing it even more squarely in the Tundra range. In my opinion, the Finley bird doesn't look much different structurally from Oregon's first Tundra Bean-Goose at the Nestucca NWR a few years ago.
I would love to hear what other anseriphiles out there think! I'd be more than happy to turn this into Oregon's first Taiga Bean-Goose, but so far, I don't see enough evidence.
Fantastic bird either way!
On Sun, Nov 25, 2018 at 7:55 PM Jamie Simmons <sapsuckers...> wrote:
> I'll stick my neck out... > The orange on the bill as shown in my pics (and better in Doug's) seems to > have a faint sliver that creeps up the bill, maybe as high as half way up > the nostril. > Also, bill size appears to be quite variable in Taiga per the Macaulay > Library. > > I'm leaning toward Taiga, based mainly on the orange on the bill. > Surely there is more that I haven't looked at, and I expect to hear more > informed opinions. > > Jamie Simmons > Corvallis > > On Sun, Nov 25, 2018 at 7:26 PM W. Douglas Robinson < > <w.douglas.robinson...> wrote: > >> Here are some pics from today of the Bean Goose. >> >> https://ebird.org/view/checklist/S50223778 >> >> Doug >> >> >> >>
-- __________________________ Hendrik G. Herlyn Corvallis, OR
*"Nature is not a place to visit. It is home." -- Gary Snyder*