Tweets,

Haven't had much time to read Tweeters lately more than skimming the digest
contents list and the odd article, so it was with great interest I saw the
latest thread on Glaucous-winged Gulls (GWGU) and Western Gull (WEGU
hybridisation, and a proposed name for the hybrid.

Reminded me of a similar discussion held locally in Vancouver BC in the
mid-80's when I proposed the name 'Puget Sound Gull' for the same hybrid for
the similar reason Bob Boekelheideof proposed, that of name convenience.
Beyond being amusedly patronised by the local birding elite, nothing much
came of the discussion and it died a natural death. I like 'Olympic Gull'
more, and agree strongly with Bob that anything which takes the
'intimidating' aspect from gull ID techniques is good. One thing that might
help is to stop calling it such: it becomes self-fulfilling. Intrinsically,
gull ID is no different from any other in that learning patterns of plumage
and getting experience looking at the things are the key. I get a great
chuckle out of hearing someone telling me how difficult gull ID is, then
watching them ID an Empidonax flycatcher using points of pattern-recognition
just as and more subtle.

Part of the difficulty is that beyond P.J. Grant's splendid book Gulls, a
Guide to Identification, there's just not the good comparative illustrations
one can take into the field of gull plumages through the Juv --> Definitive
Adult sequence. As with shorebirds, correct aging takes you 80% of the way
to a correct ID.

Bob further asks:

(snip)
>Also, are there discernible morphs of
>Olympic Gulls, depending on degree of hybridization, or do we see a
>complete continuum of plumages from Glaucous-winged to Western?

A continuum here, Bob. In fact, 'classic' WEGU is a rarity here though we
get *large* numbers of hybrids. While he was here, Al Jaramillo suggested
that there's probably no such thing as a 'pure' GWGU south of Alaska, nor a
'pure' WEGU north of northern California. Part of the problem is
conceptual-- that is, what these birds do doesn't fit our neat categories of
'species' and 'subspecies'.

Tim Eskelin says:
(snip)
>Just to fuel the gull fire a little more, in southcentral Alaska the
>common hybrid is Glaucous-winged x Herring.

Which race of Herring Gull (HEGU)? If the likely Asian HEGU race, _Larus
argentatus vegae_, then some of the hybrids will be darker-backed, and may
resemble WEGU X GWGU more than HEGU X GWGU or even be similar to Slay-backed
Gull _L. schistisagus_.

(snip)
>then one must conclude that interspecific
>barriers are quite weak for these species. Might Glaucous-wingeds
>similarly hybridize with Slaty-backed Gulls in the western
>Aleutians/Kamchatka region, or with Glaucous Gulls in the Bering Sea?

As range expansion proceeds you can bet they are, or will, unless there's
some specific isolation mechanism (i.e., one breeds on cliffs, one breeds on
gravel beds) and the challenges can only get better. Vancouver BC has seen
some *very* strange looking birds here in winter. Usually they're just
passed over as generic WEGU X GWGU, but to my eye there's more to them than
that.

I'll revive an old suggestion: lump 'em all and call it Northern Gull _Larus
Borealis_ so ornithologists can get on with the *really* important work of
establishing exactly how many races of Song Sparrow there are. ;-)


Michael Price
Vancouver BC Canada When I found out that seven of my years
(604) 668-5073 vx was only one of theirs,
(604) 668-5028 fx I started biting absolutely everything.
mprice at mindlink.net
michael.price at istar.ca -Max Carlson (Ron Carlson's dog)