Date: 4/20/19 7:16 am
From: Nicholas Mrvelj <nickmrvelj...>
Subject: [obol] Re: Crook Co. Bean-goose (a few more photos)
Aaron et al.,

First off, what an amazing find! Many congratulations!

Like others, when I first saw your photos, I immediately thought about
calling this a Taiga. The head proportions and especially the bill seemed
elongated for a “serrirostris” Tundra Bean-Goose, especially when compared
with the Finley Tundra from last Fall/Winter. The length of the neck is
somewhat hard to gauge. I feel the posture of the bird is potentially
misleading, but from what we can see, this bird doesn’t appear to have as
long as a neck I’d expect on a typical “middendorffii” Taiga Bean-Goose.
And by I’d expect, I mean based on what the literature in front of me has
provided me with, as I have no practical field experience with either
species.

Two additional things I wanted to comment on, are the grin patch and the
overall size of this bird. The former, from what we can see, appears rather
wide, ovular, and deeply recessed. This last feature, a deeply set grin
patch, seems to slightly favor “serrirostris” over “middendorffii” IMO.
Another factor in favor of “serrirostris”, is the overall amount of
yellowish coloration on the bill and it’s position closer to the middle of
the bill. According to my research, a “middendorffii” should have a more
restricted yellowish patch, farther away from the middle of the bill. My
second point, overall size, could also factor in. According to Sebastian
Reeber’s Waterfowl of Europe, North America, and Asia, “There is a
relatively strong variation in mass during the annual cycle,...being
lighter in Jan and heavier in Mar-Apr, before northward departure”. This
should come as no surprise to many of us, but I thought I’d introduce it
into the ongoing, crowd sourced analysis of this bird. I also read that
there is some slight overlap in size between the two.

A final talking point is the head shape and head coloration. The shape of
this bird’s head isn’t as flat as I’d expect on a “middendorffii” and seems
better for a “serrirostris”. Also, the coloration is somewhat dark, showing
an almost capped appearance, which during my research for the Finley bird,
I found pretty consistently on Tundra Bean-Geese and not so much on Taigas.
Not sure how reliable of a fieldmark this is, but anecdotally, it seemed to
hold up decently well.

As a side note, for those of you reading off in OBOL land and wondering
what all the subspecies talk is about, there are one additional subspecies
of both Tundra and Taiga Bean-Goose to choose from (rossicus and fabalis
respectively). However, geographic distribution aside, the size of Aaron’s
bird’s grin patch and the coloration of the bill seem to narrow it down to
the two originally aforementioned subspecies of each (serrirostris and
middendorffii) in my opinion.

I feel for the reasons stated above, this is likely a “serrirostris” Tundra
Bean-Goose, but I’d still like to see more, higher quality photos to be
completely sure of that.

Finally, I echo the thoughts of Lars and Wayne, and thought of last year’s
Hawaiian Goose and Smew in the same vicinity. It would help the process to
have photos not only of the extended neck, but also of the feet/toes if
possible, to help with the inevitable conversation pertaining to
provenance. For those of you that saw and/or documented this bird, please
consider submiting a report to the Oregon Bird Records Committee as soon as
possible.

Best,
-Nick Mrvelj (PDX)



On Fri, Apr 19, 2019 at 9:08 PM Aaron Beerman <aaron.beerman...>
wrote:

>
> A couple things stood out to me about this bird. First, it was with only
> Canada Geese, about a dozen that were sitting in the grass. Perhaps a
> trivial thing, that makes sense on this side of the mountains, but it still
> stood out to me. The previous Bean-goose in Oregon have been with Cackling
> and/or mixed flocks. Another is that to me the bill seemed a tad bit longer
> and the forehead a little less steeply sloped than the Finley and Neskowin
> birds. At most angles the head was fairly well rounded and bulbous like our
> other Tundras.
>
> I'm still leaning in the Tundra category but I'd be curious to hear what
> others thinks. I know some subspecies of Tundra and Taiga can be difficult
> to distinguish.
>
> I put together a few terrible camera phone photo of from mine and my
> parents cameras LCD screens and put them on Flickr. Unfortunately, I dont
> have a computer to download the better quality photos until Sunday.
> Hopefully tomorrow others with better optics can get some more useful
> images.
>
> https://flic.kr/s/aHsmxwaicw
>
> Cheers,
> Aaron B
>

 
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