Here are photos of the first Black-tailed
Gull (larus crassirostris) for Texas, taken at Brownsville
Dump on March 12, 1999 by Jimmie McHaney. The the lower two photos
taken February 12, 1999 are by Willie Sekula. It seems that my
assessment of this bird as a Third-Basic has caused some disagreement
- so be it, but I still feel that the following points SUGGEST
it is not a full adult - perhaps a Fourth-Basic?:-
1) White primary tips only on P5-P7; close inspection of the new
enlargments shows no white on P8-P10 with the tip of P10 (as seen
on the underside of the far wing) showing no signs of wear (i.e.
no evidence of a worn-off white tip).
2) The white trailing edge of the secondaries does not cleanly
meet the gray bases (as in published photos of adults) - instead
there are numerous blackish-gray lines "stapling" the
gray base to the white tip (see flight
shot on Greg Lasley's page for confirmation of this "piano
keyboard" effect) - similar to that illustrated for 3rd-Basic
in the Lethaby and Bangma BIRDING article.
3) The lesser and median primary coverts are have numerous black
marks, and the both the greater primary and greater secondary
coverts are strongly washed with brown (more evident in original
photo than in the scanned version, where the bases of P1, P2 also
appear to be washed brown).
4) A minor supporting feature is that the bird still has some
brownish mottling on the head in mid-March; some adult BTGUs are
white-headed by March.
5) The adult-like bill of the Texas bird can be held by Third-Basic
birds; look at the red-tipped bill of the Second-Basic bird pictured
in the Lethaby and Bangma BIRDING article.
The photo of a flying Feb adult in the Lethaby and Bangma BIRDING
article (and other published pics from Jan-March) shows clean
gray lesser/median primary coverts and small white tips at least
to P9. KEEP IN MIND that many published photos of this species
are of adults IN EARLY SUMMER, when white primary tips have usually
been worn off:
From video by John and Barbara Ribble:
