Slaty-Backed Gull

Seen above Niagara Falls (from Canada), December 2 - 2006.

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This remarkable find was made at our first stop during the 2006 Cayuga Bird Club gull watching trip
to the Niagara region. Kevin McGowan, trip leader, was the first to spot the bird at the break wall
upstream from Niagara Falls (Canada side). It was observed for ~30 minutes before flying downstream
towards the falls, where it was later refound and seen by several birders. Here, however the bird
offered good views of the distinctive wing pattern (which I was unable to photograph) - confirming
that it was indeed a Slaty-backed Gull (a life bird for myself and many others!). It took 90 minutes
or so before observers finally saw this field mark, ruling out other potential species or something
even more tricky like a Great Black-backed x Herring Gull hybrid.

For more photos, see Jean Iron's photos at: http://www.jeaniron.ca/Gulls/2006/slatybacked.htm

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First, note the dark centers to the tertials, and the extensive brown smudging - this suggests
the bird is a 3rd winter bird... almost a full adult. Major plumage differences are clear
(darker mantle, different pattern of streaking/smudging on the white parts, etc.), but also
note the color of the legs is a deeper pink than most of the surrounding gulls (photo #4).

Next, note the structural differences relative to the surrounding Herring Gulls (particularly
those in a similar position). This bird has a heavier build, a shorter hind end (short wing tips
and tail), and a "saggy bottom" look - a sort of goose-like appearance to the body caused by the
bulkier shape of the birds underside/belly and ventral area. This, in my opinion, is somewhat
exaggerated by the short hind end. Also, in photo #5 you can compare the bill structure to some of the
Herring Gulls and the Great Black-backed (bottom right) in the group. Lastly, note the broad
scapular crescent, and broad (but smudged) tertial crescent.







The above photos were taken on the break wall below the control gates above the falls.
The following shots were taken later after refinding the bird from behind the gate house.

Subject: Slaty-backed Gull - Niagara River
From: "Willie D'Anna & Betsy Potter" 
Date: Sat, 2 Dec 2006 21:53:39 -0500

We first received a call about this bird around 10:00 this morning.  A bird
found by the Cayuga Bird Club (Ithaca, NY) led by Kevin McGowan, was
described as a "possible third-winter Slaty-backed Gull" on the breakwall
below the control gates in Niagara Falls, Ontario.  (My apologies to any
other person or group who may have found this bird earlier, as suggested by
previous posts but we were not made aware of any earlier observers.)  When
we arrived at the scene about 40 minutes later, Kevin and his group were
trying to relocate it after it had flown downriver.  At this point, they
were not at all certain that this was not just a hybrid, a very real
possibility.  Shortly after, we got a call from Jim Pawlicki who had the
gull behind the gatehouse (across from Dufferin Islands).  We rushed over
and shortly, the Cayuga Bird Club also arrived.  We were fortunate to soon
see it stretch its wings - twice - and note a rather obvious "string of
pearls".  That is, this bird had a large mirror on p10, a smaller mirror on
p9, and subterminal white marks on p8, p7, and p6, forming a string of white
marks on the outer primaries in from the tips.  That is, there was black
between these white marks and the white on the extreme primary tips.  In
addition we noted the silvery-gray appearance of the flight feathers.  Other
characters noted were the bird's size - very similar to the Herring Gulls,
and shape - relatively short-winged and stocky.  The bill size was very much
like the Herring Gulls though perhaps slightly thicker but rather
parallel-sided without a pronounced gonydial angle.  There was obvious black
on the lower mandible and less on the upper mandible.  I also noted a tiny
bit of red on the gonys, just forward of the black.  The bird appeared to be
about the shade of a Lesser Black-backed Gull and later in the day, we had
nearly side-by-side comparisons with an adult Lesser to confirm that the
back (not the wing coverts which had some brownish mixed in, making them
appear paler) was actually very slightly darker than the back of the Lesser.
At different times, the "tertial crescent" looked either comparable to the
Herring Gulls or wider.  After much study at different angles, I am
convinced that it does indeed have a substantially wide tertial crescent.
The legs were a richer pink than that of the Herring Gulls.  This latter
feature was not as noticeable as it can be on adult Slaty-backed Gulls but
it was still present.  The eyes were quite pale, possibly yellow.  There was
a small bit of brownish both just in front of and just behind the eye
(characteristic of Slaty-backed Gull) as well as other scattered dark marks
on the head and hindcrown with heavier markings on the hindneck and
especially on the sides of the breast and across the belly.  The tail showed
thin streaks of dark.  In flight, there was obvious brownish on the
underside of the wing coverts.  This bird slept a lot but we also had it
take short flights several times until, late in the day, it flew out to the
middle of the river and landed amongst a larger group of Herring Gulls on a
rock a little upriver from the treed islands where the Night-Herons nest.
Although this latter spot is more than halfway across the river from Ontario
toward NY, it is still in Ontario, much to the disappintment of some of the
birders present.  Sorry for the disjointed description but it was a long
day.  Lots of digiscoped photos were taken today though I rather doubt
anyone got the wing pattern.  Hopefully, they will be posted soon.
 
Lots of gulls on the river today.  Adult CALIFORNIA GULL at Adam Beck,
Razorbill was seen early in the morning at the mouth of the river.
 
Good birding!
Willie
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Willie D'Anna
Betsy Potter
Wilson, NY

All Photos (C) 2006 Paul Hurtado
(Just let me know if you use them!)