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Subject: Great Cormorant ID
From: Kenneth Brock <kebrock(AT)INDIANA.EDU>
Date: 24 May 2000 11:33am
This is a request for assistance on the identification of immature
Great Cormorants (_P. carbo carbo_).
On May 13 of this year I observed a second-year cormorant at
the Port of Indiana (southern tip of Lake Michigan). The bird
had whitish underparts except for a bib of mottled brown
spots. The plumage was very much like the bird illustrated
on p. 93 of the _Master Guide_.
During the initial observation the bird was perched within 3 feet
of two immature Double-crested Cormorants (_P. auritus_).
Compared to the latter the bird in question was slightly larger, but
with a much larger head, bigger bill (both longer & much thicker),
a much heavier chest, and a thicker neck. In direct comparison
with the Double-cresteds the head was much less "snake-like"
and more angular.
Though the viewing conditions were distant (200m) the gular
pouch appeared more yellow than those of the birds companions.
I was unable to determine geometry of the pouch edges
on the face.
Based on information in the standard field guides, and everything
produced by a cursory search through my library, the above marks
appeared to clinch the identification as a Great Cormorant. Consequently,
I identified the bird as such, recognizing that the next nearest inland
record was in Toronto, and that this species is not prone to wander
inland.
The bird lingered for a few days and was subsequently observed
at closer range by other birders. Based on this closer view they
felt that the gular patch geometry was inconsistent with _P. carbo_,
After searching the literature more thoroughly, I finally located
an article by Alstrom (1991, _Birding World_ (4:9-16), which
deals with the issue of separating these two species in the field.
This article lists a number of field characters that separate the two
species. Some of these apply to forms other than the nominate
race. The mark that appears most useful for the P of I bird involves
geometry of the gular pouch, but not the pouch shape on the face.
According to the Alstrom article the shape of the gular patch margin
across the chin is definitive. On Double-cresteds the rear edge of
the pouch apparently make a straight line across the throat,
whereas, on Great Cormorants a "V" of feathers extends into
the pouch beneath the bill.
On the Port of Indiana bird the rear pouch edge was straight across
the chin, the situation Alstrom describes for Double-cresteds.
I have not had an opportunity to confirm the validity of this mark
by checking skins at the Chicago Field Museum.
My questions are:
1. Can anyone confirm or refute Alstroms statement about the
chin pattern of Great Cormorants?
2. Has anyone ever observed a Double-crested Cormorant similar
to the Port of Indiana bird?
Ken Brock
Indiana University Northwest
Gary, IN
Kebrock(AT)ucs.indiana.edu
[ << | >> | ^^ ]
Subject: Re: Great Cormorant ID
From: John & Wendy Cassady <wcassady(AT)SKYENET.NET>
Date: 26 May 2000 4:57pm
Ken-
The GRCO candidate was present at the Port this afternoon. It was right
next to an imm. DCCO directly north of the public access on the breakwall.
John
----- Original Message -----
From: Kenneth Brock <kebrock(AT)INDIANA.EDU>
To: <BIRDWG01(AT)LISTSERV.ARIZONA.EDU>
Sent: Wednesday, May 24, 2000 1:33 PM
Subject: [BIRDWG01] Great Cormorant ID
> This is a request for assistance on the identification of immature
> Great Cormorants (_P. carbo carbo_).
>
> On May 13 of this year I observed a second-year cormorant at
> the Port of Indiana (southern tip of Lake Michigan). The bird
> had whitish underparts except for a bib of mottled brown
> spots. The plumage was very much like the bird illustrated
> on p. 93 of the _Master Guide_.
>
> During the initial observation the bird was perched within 3 feet
> of two immature Double-crested Cormorants (_P. auritus_).
> Compared to the latter the bird in question was slightly larger, but
> with a much larger head, bigger bill (both longer & much thicker),
> a much heavier chest, and a thicker neck. In direct comparison
> with the Double-cresteds the head was much less "snake-like"
> and more angular.
>
> Though the viewing conditions were distant (200m) the gular
> pouch appeared more yellow than those of the birds companions.
> I was unable to determine geometry of the pouch edges
> on the face.
>
> Based on information in the standard field guides, and everything
> produced by a cursory search through my library, the above marks
> appeared to clinch the identification as a Great Cormorant. Consequently,
> I identified the bird as such, recognizing that the next nearest inland
> record was in Toronto, and that this species is not prone to wander
> inland.
>
> The bird lingered for a few days and was subsequently observed
> at closer range by other birders. Based on this closer view they
> felt that the gular patch geometry was inconsistent with _P. carbo_,
>
> After searching the literature more thoroughly, I finally located
> an article by Alstrom (1991, _Birding World_ (4:9-16), which
> deals with the issue of separating these two species in the field.
>
> This article lists a number of field characters that separate the two
> species. Some of these apply to forms other than the nominate
> race. The mark that appears most useful for the P of I bird involves
> geometry of the gular pouch, but not the pouch shape on the face.
>
> According to the Alstrom article the shape of the gular patch margin
> across the chin is definitive. On Double-cresteds the rear edge of
> the pouch apparently make a straight line across the throat,
> whereas, on Great Cormorants a "V" of feathers extends into
> the pouch beneath the bill.
>
> On the Port of Indiana bird the rear pouch edge was straight across
> the chin, the situation Alstrom describes for Double-cresteds.
>
> I have not had an opportunity to confirm the validity of this mark
> by checking skins at the Chicago Field Museum.
>
> My questions are:
>
> 1. Can anyone confirm or refute Alstroms statement about the
> chin pattern of Great Cormorants?
>
> 2. Has anyone ever observed a Double-crested Cormorant similar
> to the Port of Indiana bird?
>
>
> Ken Brock
> Indiana University Northwest
> Gary, IN
> Kebrock(AT)ucs.indiana.edu
>
[ << | >> | ^^ ]
Subject: Fw: Great Cormorant ID
From: Garner <Garners(AT)MEETINGHOUSE4.FREESERVE.CO.UK>
Date: 27 May 2000 6:58am
While most nominate carbo Great Cormorants seem to have the V extension of
feathering on the throat.....I wouldn't be dogmatic about this from a U.K
perspective as the subject seems to be under-researched. However the form
sinensis, which has recently been found to be more regular in Ireland has
not uncommonly a gular shape like Double-crested including a more vertical
drop of gular margin below /behind the eye and NO V -shaped intrusion of
feathering on the throat. To complicate matters our (very recent)
observations here (N. Ireland) seem have revealed indeterminate
carbo/sinensis including in regard to gular shape. Whether this is due to
variation WITHIN the forms , or some introgression is unknown. Sinensis
Great Cormorants, (particularily young birds) may disperse considerable
distances and may be a possible vagrant to Eastern North America.
A careful drawing of the gular shape of the Michigan bird would be useful.
Hope thats helpful in your deliberations
Martin
>From: Kenneth Brock <kebrock(AT)INDIANA.EDU>
>To: BIRDWG01(AT)LISTSERV.ARIZONA.EDU <BIRDWG01(AT)LISTSERV.ARIZONA.EDU>
>Date: 24 May 2000 19:38
>Subject: [BIRDWG01] Great Cormorant ID
>
>
>>This is a request for assistance on the identification of immature
>>Great Cormorants (_P. carbo carbo_).
>>
>>On May 13 of this year I observed a second-year cormorant at
>>the Port of Indiana (southern tip of Lake Michigan). The bird
>>had whitish underparts except for a bib of mottled brown
>>spots. The plumage was very much like the bird illustrated
>>on p. 93 of the _Master Guide_.
>>
>>During the initial observation the bird was perched within 3 feet
>>of two immature Double-crested Cormorants (_P. auritus_).
>>Compared to the latter the bird in question was slightly larger, but
>>with a much larger head, bigger bill (both longer & much thicker),
>>a much heavier chest, and a thicker neck. In direct comparison
>>with the Double-cresteds the head was much less "snake-like"
>>and more angular.
>>
>>Though the viewing conditions were distant (200m) the gular
>>pouch appeared more yellow than those of the birds companions.
>>I was unable to determine geometry of the pouch edges
>>on the face.
>>
>>Based on information in the standard field guides, and everything
>>produced by a cursory search through my library, the above marks
>>appeared to clinch the identification as a Great Cormorant. Consequently,
>>I identified the bird as such, recognizing that the next nearest inland
>>record was in Toronto, and that this species is not prone to wander
>>inland.
>>
>>The bird lingered for a few days and was subsequently observed
>>at closer range by other birders. Based on this closer view they
>>felt that the gular patch geometry was inconsistent with _P. carbo_,
>>
>>After searching the literature more thoroughly, I finally located
>>an article by Alstrom (1991, _Birding World_ (4:9-16), which
>>deals with the issue of separating these two species in the field.
>>
>>This article lists a number of field characters that separate the two
>>species. Some of these apply to forms other than the nominate
>>race. The mark that appears most useful for the P of I bird involves
>>geometry of the gular pouch, but not the pouch shape on the face.
>>
>>According to the Alstrom article the shape of the gular patch margin
>>across the chin is definitive. On Double-cresteds the rear edge of
>>the pouch apparently make a straight line across the throat,
>>whereas, on Great Cormorants a "V" of feathers extends into
>>the pouch beneath the bill.
>>
>>On the Port of Indiana bird the rear pouch edge was straight across
>>the chin, the situation Alstrom describes for Double-cresteds.
>>
>>I have not had an opportunity to confirm the validity of this mark
>>by checking skins at the Chicago Field Museum.
>>
>>My questions are:
>>
>>1. Can anyone confirm or refute Alstroms statement about the
>>chin pattern of Great Cormorants?
>>
>>2. Has anyone ever observed a Double-crested Cormorant similar
>>to the Port of Indiana bird?
>>
>>
>>Ken Brock
>>Indiana University Northwest
>>Gary, IN
>>Kebrock(AT)ucs.indiana.edu
>>
>
[ << | >> | ^^ ]
Subject: Fw: Great Cormorant ID
From: Garner <Garners(AT)MEETINGHOUSE4.FREESERVE.CO.UK>
Date: 27 May 2000 7:21am
Of course another feature I forget to ask about...which is a well known
go-for feature in the U.K. is the colour of the lower mandible
area...yellowish in Double-crested....ivory in both west European forms of
Great Cormorant.
Martin Garner
-----Original Message-----
From: Kenneth Brock <kebrock(AT)INDIANA.EDU>
To: BIRDWG01(AT)LISTSERV.ARIZONA.EDU <BIRDWG01(AT)LISTSERV.ARIZONA.EDU>
Date: 24 May 2000 19:38
Subject: [BIRDWG01] Great Cormorant ID
>This is a request for assistance on the identification of immature
>Great Cormorants (_P. carbo carbo_).
>
>On May 13 of this year I observed a second-year cormorant at
>the Port of Indiana (southern tip of Lake Michigan). The bird
>had whitish underparts except for a bib of mottled brown
>spots. The plumage was very much like the bird illustrated
>on p. 93 of the _Master Guide_.
>
>During the initial observation the bird was perched within 3 feet
>of two immature Double-crested Cormorants (_P. auritus_).
>Compared to the latter the bird in question was slightly larger, but
>with a much larger head, bigger bill (both longer & much thicker),
>a much heavier chest, and a thicker neck. In direct comparison
>with the Double-cresteds the head was much less "snake-like"
>and more angular.
>
>Though the viewing conditions were distant (200m) the gular
>pouch appeared more yellow than those of the birds companions.
>I was unable to determine geometry of the pouch edges
>on the face.
>
>Based on information in the standard field guides, and everything
>produced by a cursory search through my library, the above marks
>appeared to clinch the identification as a Great Cormorant. Consequently,
>I identified the bird as such, recognizing that the next nearest inland
>record was in Toronto, and that this species is not prone to wander
>inland.
>
>The bird lingered for a few days and was subsequently observed
>at closer range by other birders. Based on this closer view they
>felt that the gular patch geometry was inconsistent with _P. carbo_,
>
>After searching the literature more thoroughly, I finally located
>an article by Alstrom (1991, _Birding World_ (4:9-16), which
>deals with the issue of separating these two species in the field.
>
>This article lists a number of field characters that separate the two
>species. Some of these apply to forms other than the nominate
>race. The mark that appears most useful for the P of I bird involves
>geometry of the gular pouch, but not the pouch shape on the face.
>
>According to the Alstrom article the shape of the gular patch margin
>across the chin is definitive. On Double-cresteds the rear edge of
>the pouch apparently make a straight line across the throat,
>whereas, on Great Cormorants a "V" of feathers extends into
>the pouch beneath the bill.
>
>On the Port of Indiana bird the rear pouch edge was straight across
>the chin, the situation Alstrom describes for Double-cresteds.
>
>I have not had an opportunity to confirm the validity of this mark
>by checking skins at the Chicago Field Museum.
>
>My questions are:
>
>1. Can anyone confirm or refute Alstroms statement about the
>chin pattern of Great Cormorants?
>
>2. Has anyone ever observed a Double-crested Cormorant similar
>to the Port of Indiana bird?
>
>
>Ken Brock
>Indiana University Northwest
>Gary, IN
>Kebrock(AT)ucs.indiana.edu
>
[ << | >> | ^^ ]
Subject: Re: P. carbo in the Port of Indiana (southern tip
of Lake Michigan).
From: Graham Ekins <grekins(AT)EMAIL.MSN.COM>
Date: 27 May 2000 11:23am
This is a multi-part message in MIME format.
----INCLUDING text/plain MIME SECTION----
Ken Brock of Indiana University Northwest asked:-
> Kebrock(AT)ucs.indiana.edu
> This is a request for assistance on the identification of immature
> Great Cormorants (_P. carbo carbo_).
>
> On May 13 of this year I observed a second-year cormorant at
> the Port of Indiana (southern tip of Lake Michigan). The bird
> had whitish underparts except for a bib of mottled brown
> spots. The plumage was very much like the bird illustrated
> on p. 93 of the _Master Guide_.
Graham Ekins replies:
Hi Ken,
I have been working on a number of aspects of the biology of Great =
Cormorant here in the UK. My research has concentrated on;
1. the shape of the soft tissue below the lower mandible (that I have =
called gular tissue) as an aid to racial identification =20
(either carbo or sinensis).
2. The origins of tree-nesting birds here in England (Apart from the =
occasional record tree-nesting in England was unknown =20
before 1981).
3. The genetic structure of this population (providing tissue samples =
for Nottingham and Aberdeen University).
4. Post-fledging dispersal characteristics of the UK population using =
a colour-ringing programme.
I have a number of comments that may have some relevance to the =
appearance of the Port of Indiana bird.
Likelihood of appearance inland in North America
From ringing recoveries it is clear that carbo and sinensis can move =
considerable distances. Carbo from coastal colonies has been known to =
move 1,500km from Britain to winter off the Portuguese and Spanish =
coasts. An excellent but old paper by Coulson and Brazendale =
summarising this can be found in (1) below. Sinensis birds will move =
even greater distances. For example Dutch birds migrating to upland =
lakes in central Spain while Danish birds moving to wetlands in North =
Algeria, some 2.300km SSE. here in South East England we regularly get =
Danish and Dutch colour-ringed sinensis birds. In March 1998 I found 2 =
sinensis birds roosting in Egypt South of Aswan, again over 2,000km from =
the nearest Cormorant colony. Of the two races sinensis seems the most =
likely to wander considerable distances and even possibly crossing the =
Atlantic. This race also penetrates inland in Europe far more than =
carbo. A number of excellent papers have been published on the =
differences in movements between the races. I can provide a =
bibliography if you wish. I have no knowledge of the dispersal =
characteristics of the NE America and E Canada population of Great =
Cormorant.
Racial identity
The best and ground breaking paper on this subject is by Per Alstrom =
(2). I had his original paper translated and used it as the basis for =
my research. He suggested that the shape of the "gular tissue" below =
the lower mandible could be used to help race colonies. I have used the =
criteria successfully on 60 colour-ringed birds from known colonies =
across Britain and Europe during my field-work at Abberton over the last =
6 years and found the gular shape a reliable separator in the field.
At Abberton colour-ringed individuals from both races have nested. I am =
now getting intermediaries as well as classic forms. It is seems likely =
that introgression between the forms is occurring.
Genetic Studies
I would recommend you look at (3). It proved for the first time that =
carbo and sinensis can be separated genetically. Up to then doubt was =
cast by some researchers as to whether these 2 forms were just the =
extremes of a gradation from NE America and E. Canada.to Iceland (carbo) =
and then across Europe (carbo and sinensis) to Asia (sinensis). I would =
therefore suggest that you can use gular tissue as an indicator of race =
in many but not all individuals.
Caution
Over the last eight years I have seen 2 sinensis birds at close range =
with extensive orange gular tissue that erred towards that of D.c =
Cormorant. I have also found dead birds in Essex with both 12 AND 14 =
tail feathers. Normally in both races it is much paler, usually a cream =
or pale yellow. The angular nature of the gular tissue of pure sinensis =
Great Cormorant is closer to DcC than pure carbo.
Plumage
All of the juvenile ringed carbo seen at my research base at Abberton in =
Essex, England have very white bellies and vent. Sometimes with brown =
feathering on the flanks joining in a thin band across the upper chest. =
By contrast ringed sinensis from Sweden, Denmark and The Netherlands had =
much more extensive brown feathering on the vent and belly. Sometimes =
paler feathering in the centre of the chest could be discerned.=20
Moult
This differs significantly between the races. My work based on ringed =
individuals shows that by the first summer some sinensis have moulted =
sufficiently to be inseparable from winter adults. Sinensis may also =
start primary wing moult from September of their first autumn only 3 =
months after fledging. A characteristic I have never observed or heard =
of in carbo.
Conclusion
I would suggest that the heavy head, large bill, longer neck and greater =
size all suggest Great Cormorant. I would be fascinated to see a jpeg =
of this bird or a sketch of its head, bill and gular tissue. I have =
sketches by Alan Harris of classic examples of both forms which I can =
email if you wish.
Bibliography
1. Coulson J.C and BrazendaleM.G (1968) Movements of Cormorants ringed =
in the British Isles , and evidence of colony specific dispersal British =
Birds 61:1-21
2. Alstrom, P. (1985) Artbestamning av storskav Phalacrocorax carbo och =
toppskarv Ph. aristotelis. Var Fagelavrd 44:325-350.
3. Goostrey etal (1998) population introgression and differentiation in =
the Great Cormorant Phalacorocroax carbo in Europe. Molecular Ecology =
7:329-338.
Regards,
Graham Ekins
Tel: +44 (0) 01245 460656 Home
Tel: +44 (0) 01245 256030 Work
Mobile:07711 709 389
Pager: Ring 01399 1133 and quote 705087 and leave message
35, Church Road, Boreham, Essex CM3 3BN, UK
=20
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