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Black-tailed Gull (crassirostris)
IMAGES:
DESCRIPTION:
Adult
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 | |||
| FIRST CYCLE | SECOND CYCLE | ADULT | |
| 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 |
|
PRIMARIES (folded): |
brownish-black | as adult but A-spots smaller or absent | black w/ A-spots; A10 smaller than eye; others same or larger |
|
PRIMARIES (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 |
|
SECONDARIES (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 |