Update Dec 11,2003: The first
(distant) flight shots added at the bottom.
This adult/near-adult basic Slaty-backed
Gull (Larus schistisagus) was photographed December
3 - 9, 2003 at Lake Balmorhea, west Texas:-
This is the first image made available to me; note the following
- Rich pink legs; when LBBGs have "pink" legs they
are actually a dull fleshy tone, often with some dull yellow
mixed-in. WEGU legs tend to be less-richly colored than this,
but there is some overlap.
- Uneven, "bulbous" crown shape with two peaks; LBBG
has a smooth crown that is normally flat; WEGU tends to have
a single, smooth peak.
- Obvious, extensive yet sparse streaking on the head, with
a small dark smudge around the eye (broader ahead of it), and
fairly lightly marked auriculars; LBBG tends to have denser (and
sharper) streaking, especially on the auriculars and with a larger
patch around the eye; WEGU of this age would be completely or
- Lower neck-sides and chest marked with large, thick, blurry
blotches that - on those not in shadow - seem to have a warm
component to the tone; LBBG has thinner, cleaner-cut streaks
here, and they are cold-toned, not warm toned; WEGU would not
have these marks at all.
- Bill with medium gonydal bulge, pale pinkish at the base
with pale yellow tip to the maxilla and a pale orange spot on
the gonys; blackish smudging perhaps indicates it is not a full
adult; LBBG rarely has a pink tone to the bill base on a bird
otherwise looking as mature as this one; WEGU would not normally
show the pinkish base, and would have a much stronger gonydal
- Although in shadow, the tone of the back is clearly very
dark gray, at least; an LBBG with this dark of a mantle would
be one of the forms that is even slimmer and longer-winged than
the graellsii and graellsii-intermedius intergrade
LBBGs we normally get in North America; this apparent darkness
would be at the dark extreme for WEGU.
- Looking at the primary tips, P6 - P9 of the near wing are
visible (with P9 of opposite wing just below them) - all large
gull taxa have P10 the same legth as, often just shorter than,
or rarely just a bit longer than, P9. Thus the wing is probably
as long as it is going to get - yet it looks shortish-winged,
with the distance from the tip of the tertials to the tip of
the tail longer than the distance from the tip
of the tail to the tip of the wing - on LBBG this ratio is reversed.
WEGU is similar to SBGU in this regard.
- Even from this angle the white tips to the primaries can
be seen to be large, and broad; even on older male
LBBGs (birds that will have the most white in the primaries)
the white apical tips would be largish but narrow
- a derivative of the more-pointed tip to their primaries.
The following images have been subsequently provided by various
photographers, with permission; note the following extra points:
- The "bushy" tertials with very thick white tips;
LBBG lacks the tertial "hump" and has narrower white
tertial tips; WEGU shares the tertial humps but averages narrower
white tertial tips.
- The distinct slaty tone to the upperparts; LBBG has a leaden
tone to the upperparts, while WEGU tends to have a slightly bluer
- The underside of P9 (the longest primary; P10 is not quite
fully-grown and is visible as a large white oval a couple of
inches back from the tip of P9, on the underside of the opposite
wing) is mid-gray, not blackish; LBBG and WEGU have blackish
underside to the tips of the outer primaries.
- On the Ohl images, the tone of black/dark on the upperside
of the primaries changes from darker to paler from the outer
edge to the inner edge - a classic feature of SBGU; LBBG and
WEGU have the black of the outermost primaries of a similar dark
tone across the entire feather.
- The one difficult shot of the open inner wing suggests a
very thick white trailing edge to the secondaries; LBBG has this
edge thinner; WEGU averages thinner, but some individuals have
white secondary tips as thick as on some SBGUs.
Added Dec 11,2003: Although distant
and fuzzy, these images show a classic SBGU underwing:
- Thick white trailing inner edge such that the white tips
to the secondaries are so thick that they meet the white underwing
greater secondary coverts - with no dark gray intervening - and
the inner wing looks all-white.
- The underside of all the visible flight feathers except P10
are medium gray, not blackish or very dark gray as on all other
dark-backed gulls; the darker P10 (not quite fully-grown, with
large white tip) is a regular feature of SBGU, as shown well
in Sibley, and on page 340 of Grant's "GULLS" (2nd.
Ed.), and on some of these
Japanese SBGUs (click here) .
- Although exaggerated by blur, the white trailing edge of
the primaries is thick and extends subterminally to at least
P7/P8, with the black terminal tips to P7 - P9 contrasting with
the palish gray bases.
- The thick neck/shoulders and wide inner wing create a chunky
impression rather than a sleek impression.
Note on these
Japanese gulls (click here) that the underside of P10 is not
always contrastingly dark, and also note how the white pattern
near the tips of the outer primaries (the so-called"string
of pearls") is much more visible from below than from above
on many SBGUs.