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Subject: Re: Possible Taverner's Cackling Goose in
Pennsylvania
From: Steven Mlodinow <sgmlod(AT)AOL.COM>
Date: 19 Mar 2010 9:47am
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Greetings All
Currently, the official definition of Taverner's Goose involves two (perha=
ps three) separate populations. One breeds on northslope and, apparently,=
winters mostly or entirely east of the Rockies.
The west Alaskan populations are centered around the YK Delta and, as I re=
call, another around Kotzebue Sound. These winter in western North America=
.
This information is all contained within the article I recently co-authore=
d for North American Birds, as Alvaro knows.
Furthermore, Whistling Swans have a similar pattern. Northslope breeders=
winter in eastern North America. West Alaska breeders winters west of the=
Rockies (except some in Utah).
These populations have nearly zero mixing. Yet they are both considered Wh=
istling Swan.
Since Northslope Cackling Geese share phenotypic characteristics with West=
ern Alaska Taverner's, until proven otherwise, it seems to make sense to=
place them in the same taxon, much like Whistling Swans.
And yes, there is a lot of similarity with Thayer's Gull. Some are easily=
identifiable and some are impossible to put a name to. That is the way wi=
th much of life, and much of birding, when dealing with closely related ta=
xa, especially subspecies.=20
Just because one can not identify every bird does not mean one can not ide=
ntify most.=20
Pretty much all I've said is in the NAB article. I'd recommend reading tha=
t article rather than a long re-hashing online.=20
Best Wishes
Steven Mlodinow
-----Original Message-----
From: Alvaro Jaramillo <chucao(AT)COASTSIDE.NET>
To: BIRDWG01(AT)LISTSERV.ARIZONA.EDU
Sent: Fri, Mar 19, 2010 9:22 am
Subject: Re: [BIRDWG01] Possible Taverner's Cackling Goose in Pennsylvania
Steve
=20
Taverner=E2=80=99s was described in 1951, based on a specimen from Cal=
ifornia. If you are correct with respect to the migration being east of th=
e mountains. This really calls into question what Taverner=E2=80=99s actua=
lly is. It makes sense that north slope birds would go east, biogeographic=
ally that is. The description by Delacour of taverneri suggests it is a pa=
le bird, while most recent descriptions of Taverner=E2=80=99s make it into=
a dark breasted bird. Have you found the type specimen and seen what it=
looks like to you? My guess is that the specimen is of a funky Aleutian=
=E2=80=A6just my guess. The description of that subspecies is weak to say=
the least. I think we would all be better off if we threw out the concept=
of Taverner=E2=80=99s goose and re-assessed what those birds on the north=
slope are. My guess is that they are a larger and darker population clina=
l with Richardson=E2=80=99s, perhaps they don=E2=80=99t even deserve a nam=
e.=20
To identify an entity, a population, it first has to be well defined.=
I don=E2=80=99t think we have defined this one well at all, so count me=
as one of those who doesn=E2=80=99t think you can identify this creature=
in the field. If I don=E2=80=99t know exactly what it is, how can I ident=
ify it? And if you know exactly what it is Steve, maybe it is not what the=
taxonomic name is being applied to. This could be a chance to name Branta=
m. mlodinovi! I know to many this seems like a devil=E2=80=99s advocate=
comment, but it is not. I honestly think that the taxonomy here is screwe=
d up, and until that is resolved, how can we really identify this thing?=
It is not dissimilar from Thayer=E2=80=99s Gull, or even some of the bran=
t subspecies (Grey-bellied Brant to be exact).=20
=20
Cheers,=20
=20
Alvaro
=20
Alvaro Jaramillo
chucao(AT)coastside.net
Half Moon Bay, California
=20
Field Guides - Birding Tours Worldwide
www.fieldguides.com
From: NBHC ID-FRONTIERS Frontiers of Field Identification [mailto:BIRDWG01=
@LISTSERV.ARIZONA.EDU] On Behalf Of Steven Mlodinow
Sent: Friday, March 19, 2010 8:18 AM
To: BIRDWG01(AT)LISTSERV.ARIZONA.EDU
Subject: Re: [BIRDWG01] Possible Taverner's Cackling Goose in Pennsylvania
=20
Greetings All
=20
Sorry to disagree with David, but I do.
Typical birds, seen well, are identifiable if one uses a suite of characte=
rs, not any single one.
Both subspecies have overlapping bell curves for any given character, but=
not completely so by any stretch.
=20
And... current evidence suggests that ALL northslope taverneri may migrate=
east of the Rockies, well into the Great Plains. The fact that they can't=
put radiotransmitters on hundreds of birds means that the sample size is=
not huge. However, the presence of small flocks of typical appearing tave=
rneri in e. Colorado on a couple occasions at least suggest a long distanc=
e se. migration that could easily cause the occasional bird to head farthe=
r east.
=20
I do agree with David on this: Richardson's vs Taverneri is underappreciat=
ed, but in general, Richardson's vs Lesser is more challenging. Bill and=
head shape, which are poorly shown in specimens, are keys to identifying=
Richy from Tav, and Bannon's website does not help much there.
=20
Gular stripes can occur on all subspecies, by the way.
=20
Cheers
Steve Mlodinow
=20
-----Original Message-----
From: David Sibley <david_sibley(AT)COMCAST.NET>
To: BIRDWG01(AT)LISTSERV.ARIZONA.EDU
Sent: Fri, Mar 19, 2010 8:06 am
Subject: Re: [BIRDWG01] Possible Taverner's Cackling Goose in Pennsylvania
Devin, Mike, et al.=20
=20
I'll be the curmudgeon and say flatly that I don't think distinguishing hu=
tchinsii and taverneri out of range is possible in the field. It's fun to=
speculate, and hopefully somebody can prove me wrong, but I see so much=
variation in hutchinsii, and the differences between that and taverneri=
are so small, it just doesn't seem possible to identify one individual wi=
th any confidence.=20
=20
Browsing the photos such as Jean Irons' here: http://www.jeaniron.ca/Geese=
/index.htm or Bill Schmoker's here: http://www.schmoker.org/BirdPics/CACG=
_CANG.html shows how variable head shape, bill size, and neck length are=
among birds identified as hutchinsii. The Colorado photos might include=
some taverneri, of course, but may also include some "Western" hutchinsii=
and some hutchinsii x B. c. parvipes hybrids, and I don't know how much=
progress the Colorado birders have made on figuring all of this out in th=
e last few years.=20
=20
Pierre Bannon posted photos of specimens from the breeding grounds of hutc=
hinsii, especially a ventral view here http://www.pbase.com/pbannon/image/=
35938236 that shows how variable the breast color is on presumed hutchinsi=
i and how the darker breast can emphasize a white collar on many birds.
=20
Two hutchinsii with dark chin stripes are at http://www.jeaniron.ca/Geese/=
cackling2.htm. As far as I know this is a variable feature that is "usuall=
y" shown by some populations and "usually not" by others, but essentially=
worthless for identifying an individual bird.
=20
Another useful article is here: http://www.ofo.ca/reportsandarticles/cackl=
inggoose.php which includes the info that banded taverneri and western-bre=
eding hutchinsii have never been recovered in Ontario or anywhere east of=
the Great Plains. They could occur, and probably do, but maybe a lot less=
often than White-fronted Goose.
=20
My own summary of this identification problem (overdue for an update) is=
here http://www.sibleyguides.com/2007/07/identification-of-cackling-and-c=
anada-goose/.=20
=20
I look forward to any discussion
=20
Best,
David
david_sibley(AT)comcast.net
=20
=20
=20
=20
=20
On Mar 18, 2010, at 10:36 PM, Devin Bosler wrote:
Hello all,
=20
On 5 March 2010, I photographed an adult Cackling Goose (hereafter=
CACG) at a locally well-established Canada/Cackling Goose wintering and=
migratory stopover "hotspot" in Lancaster Co. in se. PA. The site is not=
hing more than a townhome/apartment community complete with a mid-size sha=
llow duck pond. This location has hosted thousands of migratory and winte=
ring Canada Geese (presumably both B. c. interior and B. c. canadensis) -=
along with the resident Giant Canadas (B. c. maxima) - since October 2009=
, excluding a three-week period from 10 Feb - March following two massive=
snowstorms and miserably gelid conditions. Since late October, there hav=
e been variably low numbers of CACG present, ranging from one to nine indi=
viduals per day, which is not unusual for this location. Up until 5 March=
, all of the CACG appeared to be the typical small, pale-breasted, short-n=
ecked, stubby-billed Richardson's CACG (B. h. hutchinsii) that we've becom=
e familiar with. By about 4 March, thousands of northbound Canada Geese=
began funneling back through the area and stopping at the recently thawed=
pond. Accompanying this influx of Canada Geese was a solitary Cacking on=
5 March. At the time of discovery, I originally identified the goose as=
"just" another Richardson's CACG, considering that Richardson's is the "d=
efault" taxon in the East. However, upon further review of my photos in=
addition to some background investigation into this dynamic and unsettled=
Canada/Cackling Goose complex, I feel as though this individual exhibits=
features suggestive of Taverner's CACG (B. h. taverneri). Some pro-Taver=
ner's features apparent on this bird are as follows: 1) larger-bodied than=
typical Richardson's as compared to surrounding Canadas (unfortunately no=
side-by-side comparison to Richardson's CACG). 2) longer-necked than is=
expected for Richardson's (Richardson's show proportionately short necks=
even in alert posture). 3) much darker breast imparting a prominent whit=
e collar at base of black neck (breast is nearly concolorus with rest of=
underparts and only marginally lighter than mantle. 4) more-rounded head=
shape, forehead not as steep as on Richardson's (nor is the head as small=
and blocky). 5) slightly longer-billed than expected for Richardson's.=
Overall, the impression was wrong for a classic Richardson's. But perha=
ps it's just an atypically-plumaged bird. As usual for a high-traffic sto=
pover site in March, the turnover of geese on a day-to-day basis can be re=
markable and this particular individual was not observed on subsequent day=
s. Though on 7 March, a "new" group of nine Richardson's CACG were presen=
t. I have absolutely no field experience with Taverner's CACG but perhaps=
others on this list do. Thus, I'm soliciting feedback from West coast bi=
rders/researchers with some experience pertaining to this taxon. Here's=
a link to the photos (two additional photos of Richardson's CACG are incl=
uded for general comparison): =20
http://snipurl.com/ux8no [picasaweb_google_com]=20
=20
The only other documented records of this Alaska-breeding taxon (tha=
t I'm aware of) on the East coast are from MA (? Oct 2007) and CT (30 Nov=
2007). Both of these individuals (perhaps the same bird) were well-studi=
ed and photographed. =20
=20
Thanks in advance,
Devin
--=20
Devin Bosler
Lancaster, PA
Join or Leave BIRDWG01: http://listserv.arizona.edu/cgi-bin/wa?SUBED1=3Dbi=
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