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Black-tailed Gull (crassirostris)




BLACK-TAILED GULL(18"-19"; 48"-51") crassirostris

BILL SHAPE: long w/ slightly downcurved tip; slight gonydeal angle; 4.5 times eye diameter
HEAD SHAPE: sloped forehead w/ evenly rounded crown
WING EXTENSION: quite long; about 1.5 times bill length
POSTURE/HABITS: about size of California Gull
BILL COLOR: flesh or pink w/ square-cut black tip pale yellow-green w/ black subterm band and faint reddish tip pale yellow w/ small red gon. half-spot; black subterm band; red tip
LEG COLOR: pale pinkish-brown pale green to pale yellow yellow
IRIS/ORB RING: dark pale gray to brown; orb ring dark cream to pale yellow; orb ring dark red to black
HEAD: white forehead, lores, throat, and broken eye-ring; fades into smooth unstreaked fawn brown crown, auriculars, and darker nape white w/ gray streaks across rear half, darkest across lower nape; broken white eye ring may show through gray tinge white w/ light streaks fading into a darker band from aur. edge to rear crown, giving a partial hooded or collared look; broken white eye ring may show
UNDERPARTS: smooth brown upper breast, fading to white belly and undt coverts white w/ variable g-b wash or mottling on breast sides and flanks white
brownish-black as adult but A-spots smaller or absent black w/ A-spots; A10 smaller than eye; others same or larger
(in flight):
solid brownish-black above and below as adult, but color black-brown; A-spots smaller; more black on P4-5 P7-10 black w/ small A-spots; no mirrors; P6 black outer web and base w/ A-spot; P4-5 black band w/ A-spot;similar from below, but gray paler
(in flight):
solid brownish-black w/ pale tips above and below as adult but w/ thinner trailing edge gray w/ white trailing edge, 1/3-1/2 bill length; paler from below
TERTIALS: dark brown w/ gray fringe as adult but crescents may be more washed out gray w/ faded white crescents about 1/3 bill length
GREATER COVERTS: solid med. brown w/ faded pale brown edges adult gray, tinged brown adult gray
LESSER & MED COVERTS: as tertials, but paler adult gray , tinged brown adult gray
SCAPULARS: pale gray, fading to darker brown subterminally, w/ pale fringe as adult but slight brown tinge adult gray w/ small white crescent, about 1/3 bill length
BACK: as scapulars as scapulars adult gray is medium dark, darker than Calif. Gull
RUMP: quite white w/ dark chevrons and irregular spots white white
TAIL: solid brownish-black w/ buff fringe as adult but black band broader, making tail mostly black white w/ crisp broad black sub- term band w/ jagged base; outer webs white

The was table created by Steve Hampton and is intended to futher our knowledge of gull identification. Please email me at if you have any suggestions for updating or improving this table. Thanks.