Subject: [BIRDWG01] Hybridization In Iceland and Thayer's Gulls (fwd)
Date: Jan 26 19:45:12 2001
From: ian paulsen - ipaulsen at linknet.kitsap.lib.wa.us


HI ALL:
I smell a "lump" coming!
Sincerely

Ian "Birdbooker" Paulsen
Bainbridge Is., WA, USA
ipaulsen at linknet.kitsap.lib.wa.us
"Rallidae all the way"

---------- Forwarded message ----------
Date: Fri, 26 Jan 2001 20:21:35 -0500
From: Jean Iron <jeaniron at SYMPATICO.CA>
To: BIRDWG01 at LISTSERV.ARIZONA.EDU
Subject: [BIRDWG01] Hybridization In Iceland and Thayer's Gulls

A recent paper on "Hybridization and changes in the distribution of Iceland
gulls (Larus glaucoides/kumlieni/thayeri)" was published in the J. Zool.,
Lond. (2000) 252: 517-530 by The Zoological Society of London in the United
Kingdom. The authors are D.N. Weir (deceased 15 August 2000), A.C.
Kitchener and R.Y. McGowan. I thank Michel Gosselin of the Canadian Museum
of Nature for sending me this timely paper.

Abstract follows in quotations:

"Three Iceland Gull taxa were defined mainly from adult wingtip melanism.
Up until about 1860, nominate glaucoides (no melanism) was known to breed
from Greenland to western High Arctic Canada, but by about 1900 it was
essentially confined to Greenland. Until 1860, thayeri (most melanism) was
known only from western High Arctic Canada, but from 1900 to 1980 it was
found throughout High Arctic Canada and a small part of north-west
Greenland. At high latitudes in Canada it replaced glaucoides, with which
it was formerly sympatric in the west and probably interbred. The first
known kumlieni (intermediate, variable melanism) were from west Greenland
in the 1840s, and by 1900 the western and northern limits of most of its
breeding range in the eastern Canadian Low/High Arctic were known. The
range of kumlieni lies between those of thayeri and glaucoides and overlaps
both: kumlieni bred in Greenland by 1964. It freely interbtreeds with
thayeri and probably with glaucoides. Winter ranges of glaucoides and
thayeri have changed little since they were first determined for glaucoides
by 1860 and for thayeri by the 1920s. However, winter adult kumlieni was
unknown from Greenland to the British Isles until 1900; there were a few
records prior to 1915 and progressively more after 1950. The study adds to
the evidence that kumlieni represents introgressive hybridization by
western thayeri into eastern glaucoides."

Here are some interesting statements from the paper:

1. "Compared to other hybrid and parent distribution changes in large
gulls...the extent and speed of change in Iceland gulls has been extreme."
"We believe that thayeri spread east and interbred with glaucoides, giving
rise to the variable hybrid kumlieni. As the eastward shift continued, the
hybrid zone moved east and introgression may now extend to the eastern
limits of the greatly reduced range of glaucoides."

2. "In the Iceland gull there were rapidly shifting distributions of both
parent and hybrid taxa, but kumlieni is now probably more numerous than
thayeri, and glaucoides may be 10 times more abundant than either of them."
Population estimates are 4,000 to 6,000 pairs of thayeri in Canada; 10,000
pairs + or - 50% of kumlieni in Canada; and probaby less than 80,000 pairs
of glaucoides in Greenland.

3. "...thayeri and glaucoides need not necessarily be one species; it is
only necessary that kumlieni is intermediate between them." "Whatever
taxonomic treatment is adopted, Kumlien's gull is a useful common name for
the hybrid population and it commemorates a man who made an outstanding
comprehensive study of Arctic natural history..."

This paper is based on journals and museum documents from historical and
more recent expeditions to the Arctic, examination of skins in museums, and
includes about 124 cited references.

There is a lot more in the paper than I have outlined. Students of gull
taxonomy will want to have their own copy of this paper, which is the most
significant addition in years to the ongoing discussion about Iceland,
Kumlien's, and Thayer's Gulls.

Ron Pittaway
Minden, Ontario


Jean Iron
President, Ontario Field Ornithologists
9 Lichen Place
Toronto, Ontario M3A 1X3
Canada
Phone: 416-445-9297
e-mail: jeaniron at sympatico.ca
Web Page: http://www.interlog.com/~ofo