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Great Black-backed Gull (marinus)


First Cycle
Second Cycle


GREAT BLACK-BACKED GULL (28-31";60-66") marinus

BILL SHAPE: very large and deep; 5-6x eye diameter; gon angle moderate; culmen straight w/ steep vertical hawk-like tip
HEAD SHAPE: large w/ long flattish crown, so that eye appears tiny; heavy brow
WING EXTENSION: 3/4 - 1x bill length
POSTURE/HABITS: obviously larger than Herring w/ heavier, more lumbering flight
BILL COLOR: black, sometimes w/ slight pale base; often w/ tiny white tip variable; usually pale at base; dark subterm band or larger dark area; pale tip whitish to yellowish-pink w/ variable dark subterm marks; often hint of gon spot pale yellow w/ orange or red gon spot
LEG COLOR: dull pink dull pink usually as adult pale grayish-pink or flesh
IRIS/ORB RING: dark dark or pale as adult pale yellow, but often dark from a distance; orb ring red
HEAD: quite white w/ some streaking on rear crown, rear aurs, nape, and neck sides; dark crescent from front of eye, under eye, to short postocular line white w/ faint streaking around eye and rear aurs; streaking on nape and neck sides; dark eye crescent as adult mostly white; dark eye crescent and thin dark streaks on rear aurs and nape visible at close range
UNDERPARTS: breast white or lightly speckled; belly and flanks boldly blotched white w/ mottling from breast sides down flanks largely white; may have faint marks white
blackish; pale crescents at tips in fresh plumage blackish; pale crescents at tips in fresh plumage as adult but A-spots may be smaller all A-spots larger than eye
(in flight):
dark w/ moderate pale window on inner Ps, more notable from below dark w/ moderate pale window and dark subterm marks on inner Ps; trace of mirror on P10 possible as adult but more black and smaller mirrors, often not terminal; black often to P5 large terminal mirror on P10; large mirror on P9 (rarely terminal); rarely small mirror on P8; black band on P6; slender white tongue on P6, sometimes to P7 or even P8; very dark contrast from below
(in flight):
dark w/ pale fringe blackish w/ broad pale fringe as adult adult gray w/ broad white trailing edge, about 1/2 bill length; often show pale bases from above when worn
TERTIALS: dark g-b w/ large white tip, edges, and single large notch on sides dark g-b w/ extensive marbled and white tips mixed adult gray and brown w/ large white tip adult gray w/ large white crescent, about 1/2 bill length
GREATER COVERTS: white w/ rows of dark g-b spots; outer webs more solid dark on outer feathers entierly marbled dark g-b and white, w/ obvious white subterm spot or bar mixed adult gray and brown, especially inner feathers adult gray
LESSER & MED COVERTS: pale w/ large dark g-b subterm anchor, appearing checkered pale w/ dark subterm anchor, appearing checkered or barred adult gray w/ brownish tone adult gray
SCAPULARS: as L&M covs as L&M covs; may show little or no adult gray adult gray; may have brownish fringes adult gray w/ small white crescent; about 1/3 bill length
BACK: as L&M covs, but narrower edges creates darker look as scapulars; adult gray by summer as scapulars adult gray is very dark, nearly black
RUMP: white w/ faint scattered streaks; dark arrowheads around tail base largely white white white
TAIL: white base w/ irreg. jagged black subterm band w/ thin wavy inner band and other spots; outermost webs white white w/ large variable mottled subterm band; outermost webs white white w/ variable broken subterm band or marks; outermost retrices white white