ID-FRONTIERS for March 14-20, 2010

Messages are displayed in the order they were received.  Subject  From  Date   Time   Re: Possible Taverner's Cackling Goose in Pennsylvania   Steven Mlodinow    Fri, 19 Mar 2010   9:47am

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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

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