From ID Frontiers
Dma3@aol.com
Tue, 9 Mar 1999 15:19:02 EST
Hi Ospreyers:
For those who have not seen the latest from Bird ID Frontiers, here it is.
There are a lot of experienced observers who think that the paler Slaty-backs,
including photos in some of the field guides, and some of the birds in the
gull video, are simply hybrids. As with thayeri, it looks like we need still
more work. Bob Lewis just added some Slaty-back photos from Siberia to his web
site. Those are very dark, and may be the best examples of true Slaty.
Dave Czaplak
Subj: Re: [BIRDWG01] Slaty-back mantle color
Date: 3/9/99 12:33:24 PM Eastern Standard Time
From: alvaro@SIRIUS.COM (Alvaro Jaramillo)
Sender: BIRDWG01@LISTSERV.ARIZONA.EDU (NBHC ID-FRONTIERS Frontiers of Field
Identification)
Reply-to: alvaro@SIRIUS.COM (Alvaro Jaramillo)
To: BIRDWG01@LISTSERV.ARIZONA.EDU
At 12:07 PM 3/7/99 EST, Dave Czaplak wrote:
>
> I thought that everyone was aware that there are two "flavors" of
Slaty-
>backed Gull. Here is the background for those who were not. Dwight described
I would really disagree here. First of all to my knowledge no one has
actually unambiguously shown that Slaty-backed Gulls are multi-flavoured.
Where are the data? Where was this quantified?
IN fact, all available information from Asian observers that I know of
suggests that Slaty-backed Gulls are 1) dark and 2) not very variable in
mantle colour. There are Slaty-backed Gulls which are paler, but these are
found in North America. Now the question is, are these really Slaty-backed
Gulls?? I would predict that if you asked an experienced Asian observer how
often a Slaty-backed Gull is as paler or paler than a graellsii Lesser
Black-backed Gull they would reply, "never, that was not a Slaty-backed
Gull". For all of you who are interested in this subject, it is quite
likely that a paper will appear in the Canadian magazine Birders Journal on
this in the future.
> Mary Gustafson and Bruce Peterjohn wrote an excellent article in
the August
>1994 issue of Birding, which covers this variation in detail. (Hereafter
>referred to as GP.) Figure 6 shows the complete range of variation in mantle
>color of specimens from the USNM (Smithsonian). Birds in the video and in
Below I have included a note I wrote over 4 years ago on the subject of the
Birding Slaty-backed Gull article. I think that this paper has been very
good in inciting discussion, but it probably is not the final word on
mantle paleness in this species. The fact that birders have assumed the
paper to be gospel, may have confused aspects of Slaty-backed Gull
identification in the continent.
> So why does Slaty-back have two flavors? To quote GP: "Whether this
>geographic trend indicates a cline, with darker birds in the north blending
>into paler birds nesting farther south, a hybrid swarm, or an undescribed
>subspecies, remains to be determined." Slaty-backed is reported to hybridize
>with vegae Herring Gull around the Gulf of Anadyr (Handbook of Birds of the
>World, vol3), and its range also overlaps that of Glaucous-winged Gull.
If this relationship is still to be determined. Why not be conservative and
assume that birds that are too pale, are not Slaty-backed Gulls?
Apparently, hybridization between Slaty-backed and Glaucous-winged is now
known (this has been covered on this list before) and perhaps its not as
rare as thought?
It is
>possible that this group of gulls forms a chain of intergradation
analogous to
>that of the Herring--Glaucous-winged--occidentalis Western--wymani Western
>Gulls of the Pacific coast of North America. It has been several years
since I
This is off the topic, but there really isn't a chain of intergradation.
The changeover between wymani and occidentalis Western Gulls is rather
abrupt. This is partially due to the fact that in the area where the
subspecies change there are very few breeding birds. The only area where
intergradation occurs is the Puget sound region where the two species
hybridize. The fact that occidentalis Western Gull is paler than the
southern wymani does not appear to have anything to do with Glaucous-winged
Gull genes being involved (Doug Bell pers. comm.- I hope I did not
misinterpret what he told me).
Here is the ancient note:
Date: Tue, 7 Mar 1995 11:30:39 -0800
From: Alvaro Patricio Jaramillo <jaramill@SFU.CA>
Subject: Slaty-backed Gull, Japanese perspective
Dear Chatters, tweeters and obolers:
The observations of Yellow-legged gulls, hybrids, and weird stuff mentioned
in birdchat has me salivating! Gull watching in North America is getting
seriously interesting. Another potential Kelp Gull, wow!
Yesterday I had the opportunity to go birding with Nial Moores a Brit
who has been living in Japan for four years, and doing a lot of birding
both there and in South Korea. It didn't take long to realize this guy
was both really sharp and a gull 'freak'. We went out around the Vancouver
area for a few hours looking for gulls. All we talked about was gulls,
gulls and more gulls, it was a joy.
We started out near Boundary Bay looking for the large flock that
roosts in the fields, this is the flock where I found a Slaty-backed a
couple of weeks back. We found the flock and located the Slaty-backed and
a couple of Westerns in with all of the Glacous-winged and hybrids. Once
he had studied the Slaty-backed Gull, he mentioned that the bird was
totally typical in every respect except the fact that it was in a field.
In Japan, Slaty-backed is seldom found away from rocky coasts! He noted that
the mantle colour was totally typical for Slaty-backed. Referring to
the recent paper by Mary Gustafson and Bruce Peterjohn (Birding XXVI:243-
249, 1994) that outlines the variation in mantle colour in Slaty-backed,
I qualified his statement by asking if he meant typical to mean average.
He replied, no typical because they don't vary in mantle colour! Now I
was confused. His experience looking at thousands upon thousands of
Slaty-backed Gull in the field was that they are quite standard in mantle
colour, at least in Japan and Korea. When he has found paler birds, upon
closer examination they have turned out to be dark Herring Gulls! In
Japan, they get several forms of Herring in winter, with vegae being the
most common. Fortunately, I had brought the article with me and showed it
to him. He was amazed and very incredulous. He disagreed with the statement
that vegae 'may be paler or darker than a pale Slaty-backed Gull' (caption
on figure 7. His observations are that vegae are always paler than slaty-
backed, darker Herring Gull types he has seen in Japan are birds from
further west (tamyrensis and mongolicus???). We studied the article, especi
ally figure 6 which shows the range in Slaty-backed. I noticed something
really odd. The two bird on the left, the dark ones have streaked heads,
the two on the right have pale heads. This implies that the two birds
on the left were taken in winter when they have less worn plumage than
the birds on the right. The primaries on Slaty-backed are black, so now
look at their colour in the photo. The two birds on the right have paler
primaries than the birds on the left, roughly paralleling the paleness
differences of the mantle. All of this suggests that the birds on the
right are paler due to wear, not due to variation in the mantle colour.
This would fit his interpretation of Slaty-backed mantle colour. The
article does show some variation in mantle colour of wild birds, but to
some extent this may be due to the angle of the birds in the photo. Have
a look at figure 4, the darkest bird appears to be most perpendicular
to the observer. The bird in front is turned somewhat toward the observer
, note that the sun is to the left. The tertials and hind scapulars look
paler on this bird, but likely because they are more perpendicular to
the rays of the sun. The two bird in the background are turned even more
perpendicular to the direction of the light and they look even paler. The
bird in figure 5 looks pale since the light is coming from behind the
photographer, check out the shadows.
I don't mean for this posting to be an attack on the paper, I think
it has been greatly useful in educating us about Slaty-backed Gulls. Yet,
Nial's comments suggest that something weird is going on. I have several
friends that have spent lots of time in Alaska and they mention that there
are lots of dark mantled birds they cannot identify up there, they have
thought that these birds may be hybrids (which has not been observed anywhere
as far as I know) with Herring Gull as they are paler than good slaty-backs.
Nial suggested that we may be overlooking other subspecies of Asian
Herring Gull here in North America and passing them off as Slaty-backs.
He noted that Mike Force's shot of a bird here in Vancouver (Figure 3) looked
rather un-slaty backed like. Could this be a different Herring Gull type?
Aparently the situation with Asian Herring Gulls is much more complex
than what is mentioned in Grant. This is the observation of Japanese and
Hong Kong birders, the Herring Gulls in Hong Kong have recently been
realized to be of a completely different subspecies than they had thought
before, I wish I had written down the exact details.
Well all of this has really 'rocked the foundations' of my gull watching
assumptions. Does this frighten me? No way, now I want to watch more gulls.
I hope that these comments may incite some good gull discussions.
good.birding
Alvaro Jaramillo "It was almost a pity, to see the sun
Half Moon Bay, shining constantly over so useless a country"
California Darwin, regarding the Atacama desert.
alvaro@sirius.com
Helm guide to the New World Blackbirds, Birding in Chile and more, at:
http://www.sirius.com/~alvaro
----------------------- Headers --------------------------------
Return-Path: <owner-birdwg01@LISTSERV.ARIZONA.EDU>
Received: from rly-za01.mx.aol.com (rly-za01.mail.aol.com [172.31.36.97]) by
air-za05.mail.aol.com (v56.26) with SMTP; Tue, 09 Mar 1999 12:33:24 -0500
Received: from LIME.EASE.LSOFT.COM (lime.ease.lsoft.com [209.119.1.41])
by rly-za01.mx.aol.com (8.8.8/8.8.5/AOL-4.0.0)
with ESMTP id MAA05274;
Tue, 9 Mar 1999 12:33:05 -0500 (EST)
Received: from PEAR.EASE.LSOFT.COM (209.119.0.19) by LIME.EASE.LSOFT.COM
(LSMTP for Digital Unix v1.1b) with SMTP id <14.0015C2B5@LIME.EASE.LSOFT.COM>;
Tue, 9 Mar 1999 12:31:34 -0500
Received: from LISTSERV.ARIZONA.EDU by LISTSERV.ARIZONA.EDU (LISTSERV-TCP/IP
release 1.8c) with spool id 8280756 for
BIRDWG01@LISTSERV.ARIZONA.EDU; Tue, 9 Mar 1999 10:30:59 -0700
Received: from mail2.sirius.com (mail2.sirius.com [205.134.253.132]) by
listserv.arizona.edu (8.8.8/8.8.8) with ESMTP id KAA23782 for
<BIRDWG01@LISTSERV.ARIZONA.EDU>; Tue, 9 Mar 1999 10:30:57 -0700
Received: from alvaro (ppp-asfm12--087.sirius.net [205.134.231.87]) by
mail2.sirius.com (8.9.1/8.9.1) with SMTP id JAA04809; Tue, 9 Mar
1999
09:30:52 -0800 (PST)
X-Sender: alvaro@sirius.com
X-Mailer: Windows Eudora Light Version 3.0.1 (32)
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Message-ID: <3.0.1.32.19990309092442.00ab4f9c@sirius.com>
Date: Tue, 9 Mar 1999 09:24:42 -0800
Reply-To: Alvaro Jaramillo <alvaro@SIRIUS.COM>
Sender: NBHC ID-FRONTIERS Frontiers of Field Identification
<BIRDWG01@LISTSERV.ARIZONA.EDU>
From: Alvaro Jaramillo <alvaro@SIRIUS.COM>
Subject: Re: [BIRDWG01] Slaty-back mantle color
Comments: To: Dma3@AOL.COM
To: BIRDWG01@LISTSERV.ARIZONA.EDU
In-Reply-To: <784a4090.36e2b266@aol.com>