Date: 8/25/19 7:55 am
From: Jelmer Poelstra (via carolinabirds Mailing List) <carolinabirds...>
Subject: Re: exciting gull at Falls Lake
Hi all,

I first noticed this Gull from Rolling View yesterday at about 4:20 pm,
within a group of Common Terns, but soon went to Sandling Beach since the
birds were much closer to that shore. That turned out to be a bad choice,
as the group had moved westwards *passed* Rolling View by the time I
arrived at Sandling. They did come back to the area between Rolling View
and Sandling Beach several times but never close by. I don't think I ever
saw the bird closer than at about 1-2,000 ft. but did see it for extended
periods of time (15+ minutes in the scope).

I tried to take both pictures and phone-scoped videos of the bird when the
group got a little closer but failed -- the bird wasn't identifiable among
the mass of terns on the phone or camera screen. This just got me very
frustrated as I was missing opportunities to see the bird better. I also
attempted to post to Carolinabirds soon after I first saw the bird, by
replying to Brian B's message, but in my haste only replied to him.

A couple of the features noted:
* Striking black W on upperwing.
* Outside of the W, the upperwing appeared pale. Thus on the arm, there was
pale both in front of the diagonal band (i.e., not at all a
Sabine's-patern) and behind it, with entirely whitish secondaries (e.g. not
the black trailing edge of Bonaparte's).
* Obvious shoulder patch reminiscent of Black Tern, likely continuing up
the top of the neck.
* No obvious dark on head.
* Gray back that appeared unmarked.
* Black terminal tail band, though I am unsure whether it went across the
entire tail or was limited to the central tail feathers.
* Rather similar in size to the Common Terns it was flying amidst, but
slightly smaller, both in terms of body size and wingspan.
* Flight style also very similar to the Common Terns, but slightly
flappier. (I did note it first by flight style and then noticed the W when
zooming in. Nevertheless, the flight style in combination with the size
made it surprisingly easy to overlook at a distance among the terns.)

I went back-and-forth on the ID. I initially identified it as a Kittiwake,
taking the black shoulder patch to be diagnostic. But as I started paying
more attention to the fact that the bird was slightly smaller rather than
clearly bigger and bulkier than the Common Terns, that seemed untenable. I
still excluded Little Gull based on the shoulder patch, white secondaries,
and no apparent dark on the head -- and when I thought I saw that the black
on the tail was limited to slightly protruding central tail feathers, I for
a while thought Ross's.

However, I had completely overlooked the fact that juvenile Little Gulls,
before moulting to the 1st winter plumage we are more used to seeing them
in, do have a big dark spot on the upper side of the breast. Moreover,
looking at some pictures of various 1cy Little Gulls, the dark secondary
markings seem rather variable and can be absent or nearly so. Finally, the
appearance of a pale head can possibly be blamed on the distance (i.e.,
overlooking the cap). But to keep things puzzling all the same, an
unmoulted juvenile Little Gull should, in addition to the black shoulder
patch, also show dark markings on much of the back -- and the back appeared
an unmarked gray. Can the dark back molt to gray before the shoulder patch?

All in all, I think the size as described fully excludes Kittiwake, and
think the bird is most likely to have been a Little Gull. But given some
puzzling apparent features of the plumage, I still have trouble excluding
Ross's, however unlikely. But any feedback is welcome! (For instance, I
wonder if the timing of breeding and dispersal would make a 1cy of any of
these 3 species a priori out of the question as early as late August.)

I also briefly saw an adult Laughing Gull flying east to west almost right
over Rolling View before I noted the other gull, so plenty of excitement
going around from the get-go. Otherwise, the 3 Black Terns that Brian B.
reported earlier were still there, as were at least 4 Caspian Terns and a
single Forster's Tern, making for four species of tern.

Good birding,

Jelmer Poelstra
Durham


On Sat, Aug 24, 2019 at 9:09 PM bruce young <carolinabirds...> wrote:

> Jelmer Poelstra reported a juvenile Black-legged Kittwake around 5:00 and
> I got there a little after 6 right about the time he postulated it might
> just be a Ross's Gull (!!!). At that point he was at Sandling beach and I
> was at Rolling View. Brian Bockhahn joined me maybe 30 minutes later.
> I had one sustained 4-5 minute view and a couple of shorter ones in my
> scope of the flying bird. It was never exactly close and I was near top
> power on my scope (60x) for most of it and the birds did not stop at any
> time. It was a gray day with night coming on.
> I believe it was a Kittiwake.
> It was flying mostly with a group of Caspian Terns. It was noticeably
> smaller and more compact than them. There were a couple of Common and at
> least 1 Black Tern around but I never got a good size comparison with them.
> The most noticeable plumage feature was the broad black M across the wings
> comprising the front of the wings to the outer primary tips then back to
> the base of the wings through the coverts. The M was not neat more messy
> and broad. Other than the outer primaries the rest of the flight feathers
> were pale. Mantle was light gray. Underwings pale
> The tail was square with a black band going clear across the tail from
> side to side.
> There was a small black ear patch and a larger black area on the side of
> the neck which may have met as a collar in back but couldn't really tell.
> Other than Ross's, Little and Sabines were also mooted. Sabines is out
> with the pale mantle and full black M. I believe Ross's is out based o n
> the tail shape, the black bar going all the way across the tail and the
> black collar. Little Gull is tougher. There was a lot of black on the top
> of the wing but I didn't see a black patch at the base of the secondaries
> or a black cap and I did see the black collar especially on the sides of
> the neck. Plus I don't think it was quite that small.
> Bruce Young
> <byoung715...>
> Durham, NC
>


--
Jelmer Poelstra
311 Biological Sciences Building, Biology Department
Duke University Durham, NC
Email: <jelmerpoelstra...> / <jelmer.poelstra...>
Phone: (+1) 919-260-8253

 
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