Sabine's Gull at Mori Point follow up


Eddie Bartley
 

To Pen Birders, SF Birders and especially the GGA field trip participants:

My bad for not better documenting to the public when I posted the Dec. 6,
2009 sighting of a Sabine's Gull off Mori Point. I knew that the encounter
was very uncommon but didn't realize just how rare a December sighting of a
Sabine's Gull was until I started doing research. Having heard about quite a
few October sightings of Sabine's Gulls guess I wasn't as shocked as I
should have been. In any case, I should have tried to get someone to
photograph the bird and this rare account will probably be lost to county
and state records because of that. My apologies to those diligent and
thoughtful folks that compile that valuable data. My only excuse for not
properly posting is being completely slammed with prior commitments and just
haven't had much time to devote to the report but here, albeit belated, is a
more detailed account from my notes penned when I returned home and memory
for any who are interested:

The GG Audubon group convened at 8:00 AM for a tour of the Mori Point and
Sharp Park preserves and made it up to the cape of Mori Point at about 10:15
AM, relieved that the prominent bluff partially sheltered us from the cold
and high winds. There were many hundred of loons, also many scoters, grebes
especially in the mini-bay to the south of the point which I attributed to
the changing weather. Howard Higley spotted a group of three Black Scoters
which we then scoped: one male and two females. After maybe a minute the
subject gull, strikingly small in comparison to the Scoters drifted within 5
feet of the three Black Scoters. All of these birds were on the leeward side
of the point so the water was fairly smooth and high clouds made for
excellent viewing with little contrast to the light. The bird was easily
seen with good binoculars, not more than 150 feet out and we had a Zeiss
85mm scope which we took turns looking through. Naturally, we ensured all in
the sizeable group got a good look through the scope at the rare sighting.
The primary observers and debaters were myself and Howard Higley. Other
experienced birders who had great looks at the bird included Jeff
Fairclough, Laurie Graham and Noreen Weeden. I don't think any present have
extensive experience with this species and I have never seen them in winter.


Kittiwake was the first quick guess by both Howard Higley and myself before
we scoped the bird (I was using binos when the bird drifted in and Howard
exclaimed "What about that gull!?"). We had 10 plus minutes with the bird,
both Sibley and NG Field Guides out. The first thing that popped out at us
was the head: brownish on the cap and back of the neck, white forehead, face
in front of bill and throat. No appreciable auricular mark/dot as in Ross's,
Bonaparte's, Kittiwake, etc. The relative size to the Black Scoters who were
within five feet reduced the possibilities considerably. It was a tiny gull
with very long black primaries that projected upwards, rather tern like in
structure. The bill itself appeared all black, a shallow curve at the end of
the upper mandible and a very slight gonydeal curve on the lower. The shape
eliminated Ross's (tiny bill) and Red-legged Kittiwake (bill too long
relative to head size for Red-legged Kittiwake) with the upper and lower
mandibles appearing almost symmetrical. The head shape and bill structure
was identical to Sibley's illustration of Sabine's Gull and what led me to
consider it. As we observed the gull, we spoke out loud the characteristics:
All black bill, head mottled brown on the cap and back, white face and
throat. Gray back (mantle, scapulars, coverts) which confused us as there
were no comparable illustrations in our guides. The length of the all black
primaries extending well beyond the tail were greater than what is shown on
both Kittiwakes and right in line with Sabine's. More curious was that the
mantle, wings and the folded wing pattern which resembled Sibley's 1st
summer pattern to me more than 1st winter in the amount of white shown at
the base of the folded primaries (the inner primaries) and especially the
apparent lack of brown anywhere on the coverts which might be expected in a
bird transitioning from juvenile to first adult. I don't yet own the new
"ID Guide to NA Birds II" (Pyle) and am unfamiliar with Sabine's molt
sequence but Sibley's notes suggests juveniles transition to first adult
plumage by January.

Anywho, after considering all of the possibilities based on apparent size
and overall structure including head shape, bill shape and color, length of
primaries in relation to tail, arrangement of plumage and color and then
comparing these characteristics to the illustrations in our guide books, the
Sabine's call was made and eventually accepted. Admittedly I was the first
one to suggest Sabine's (and being the leader that could possibly have
biased other's opinion) but we had another five minutes with the bird after
that suggestion and none of the observers thought differently at the time. I
tried for a couple of minutes to turn it onto the other comparable gulls
using the guides and the more I looked, the more I was convinced it was a
Sabine's Gull and that was while we were still viewing the bird.

After perusing many images of comparable illustrations and images of similar
gull species, especially Kittiwakes, that same afternoon and subsequently,
I'm still confident in the call. Friends have suggested that it was more
likely that we spotted a Red-legged Kittiwake but, in all due respect, I
think there are quite a few differences, especially in bill structure (which
I always use as the number one factor when identifying closely related
shorebirds - plumage varies but bill structure, rarely) and folded outer
primaries (length in relation to the tail) between these two species. Also,
the cap and back of the neck were certainly brown, not gray or white - I
haven't found any images or illustrations of Kittiwakes with that plumage.
Naturally I'm happy to reconsider if images of Kittiwakes or other small
gulls come about that throw some doubt in my mind but as of now, I still
believe we saw a very rare sighting of a transitional Sabine's Gull.

Happy Trails!

Eddie Bartley

-----Original Message-----
From: notify@... [mailto:notify@...] On Behalf Of
squirtz72
Sent: Tuesday, December 08, 2009 8:25 PM
To: Eddie Bartley
Subject: Re: Mori Point & Sharp Park

Hi, Eddie

I have been getting a a lot of emails about the Sabine's Gull, so I told my
correspondents that you were the person who ID'd the gull. Have you been
getting any flack from anyone, specifically Ron Thorn or Joe Morlan?

I would like to know how you decided on the ID. I was so cold at the time
that I wasn't paying attention to the discussion, and am ashamed to say that
I saw the bird stretch its wings and couldn't tell you what they looked
like.

Thanks

Laurie

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