[obol] Re: Cackling goose (Aleutian form)
- From: Scott Carpenter <slcarpenter@xxxxxxxxx>
- To: obol <obol@xxxxxxxxxxxxx>
- Date: Tue, 14 Oct 2014 21:48:57 -0700
Hi Marlowe,
One way to pick out Aleutian Cackling Geese within a flock of mixed
Cacklers is to look for a bird that is roughly the same size as the
Ridgway's (minima) Cacklers, but with the following differences:
- Ridgway's will have a dark chocolate/purplish breast and a rounded head
- Aleutian will have a relatively light breast, and a (most of the time)
squarish head
- Both will have very small bills and heads, noticeably smaller than Lesser
Canada
- Aleutians tend to have thicker gular stripes than Ridgway's; the gular
stripe is the black line on the white part of the throat, so this can be
hard to see.
Taverner's Cackling Goose and Lesser Canada Goose also have relatively
light breasts, but are larger than Ridgway's and Aleutian. All of this
said, keep in mind that there is much variation (breast color, head
size/shape, bill structure, etc.) within the entire Canada/Cackling
complex, particularly among all races of Cackling geese, and Lesser Canada
Goose. Some birds are best left unidentified.
As for separating Taverner's from Lessers, it is worth noting that for
official goose survey data, USFWS does not distinguish between the two --
there is one slot for Ridgway's (minima), and another slot for Tav/Lesser,
and another slot for Western Canada. I've talked to multiple biologists who
have held live and/or dead birds in their hand and not been able to
distinguish between the two with the naked eye. Mixed flocks with birds on
the extremes of plumage can make it easier, but many are best left
identified as Tav/Lessers.
Also, many hunters and biologists will use the term "Cackler" to refer to
Ridgway's (minima). I believe this is leftover from when the entire
white-cheeked complex was considered one super species, the Canada Goose.
Knowing this can help sort through some of the information that is out
there.
I have some photos of the Aleutians that winter in that one field in Oregon
online at
http://www.scottcarpenterphotography.com/cacklinggoose/h2bd11b4d#h33843120
-- the blocky head is quite apparent in some, but not all, of the photos.
The neat thing about this particular field in Tillamook County is that you
can study Dusky, Lesser, Taverner's, Ridgway's, and Aleutian (and maybe
even Western) at once, and many of the Aleutians have green collars, so you
know what you are looking at. A couple of hours staring at birds in that
pasture can be quite instructive when learning how to identify the
different races.
--
Scott Carpenter
Portland, Oregon
-------------------------
http://www.scottcarpenterphotography.com/
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