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Thayer's Gull

Note: "Kumlien's Gull" is considered here to be Iceland x Thayer's hybrid and is in the hybrid section. See this page for a note on taxonomy and a proposed Thayer's/Kumlien's/Iceland scoring system.


First Cycle
Second Cycle
Third Cycle


THAYER'S GULL (22-25"; 50-55") thayeri

BILL SHAPE: short, thin, and straight; about 3-4x eye diameter; little gon angle; curve of culmen is gentle
HEAD SHAPE: smooth and often very rounded, somewhat dainty or dove-like; sometimes w/ sloped forehead
WING EXTENSTION: slightly longer than bill length
POSTURE/HABITS: slightly heftier than Iceland, smaller than Herring
BILL COLOR: solid black; some w/ flesh base to lower mandible pale flesh w/ variable dark tip; some may be mostly dark variable flesh to yellow w/ dark tip or subterm band; may show some gon spot pale yellow, may have greenish tone w/ brighter tip; gon spot red to orange-red, small and flat, not extending to cutting edge; rarely w/ dark mark
LEG COLOR: dark pink dark pink dark pink dark rose pink
IRIS/ORB RING: dark usually dark usually as adult iris usually dark; may be honey or even yellow; orb ring
HEAD: covered w/ thin diffuse g-b streaks; aurs often solid; pale on aur edge, upper nape, near bill and on throat white w/ fine light streaking on crown and aurs; heavy blotching often around nape to breast sides as adult but w/ more extensive streaking over head, neck, and upper breast light streaks on crown and aurs, paler and browner than on smithson; extensive thick blurred streaks on lower nape to breast sides
UNDERPARTS: breast fairly uniform pale g-b, diffusely streaked or splotched; belly uniform and slightly darker; undt covs barred variably smudged, especially on belly; undt covs lightly barred white; some splotching from breast may extend to belly white
dark g-b w/ pale crescents of feather tips, sometimes worn off by late winter variable gray w/ pale crescents as adult, but w/ smaller A-spots A-spots evenly sized or slightly decreasing; A7 slightly larger than eye; A10 same size or slightly smaller than eye
(in flight):
outer webs of outer Ps dark, inner webs light, producing a striped effect; pale window on inner Ps; silvery pale from below w/ thin dark trailing edge to outer Ps as juvenile but w/ pale webs nearly white; inner Ps nearly white; thin dark trailing edge to outer Ps from below, otherwise quite white ... limited black on Ps; huge terminal mirror on P10; large mirror on P9; black confined to outer webs and subterm bands on P5-9; large white tongues on P6-8; pattern much fainter from below, showing dark gray subterm bands only; gray undersides show little contrast
(in flight):
like Ps, outer webs dark and inner webs light, but w/ pale fringe; silvery pale from below washed g-b outerwebs and pale inner webs w/ pale fringe; whitish from below ... adult gray w/ white trailing edge about ½ bill length
TERTIALS: usually a little darker than covs, lighter than Ps; solid g-b w/ variable pale subterm marks and pale tip; some w/ pale notches along sides med g-b w/ extensive white marbled tips and fringes adult gray; may have trace of g-b adult gray w/ white crescent about 3/4 bill length
GREATER COVERTS: completely barred or spotted g-b and white, appearing checkered white w/ irreg fine brown barring or marbling adult gray; may have trace of g-b adult gray
LESSER & MED COVERTS: like scaps, but w/ smaller anchors, appearing neatly checkered white w/ irreg fine brown barring or marbling adult gray; may have trace of g-b adult gray
SCAPULARS: pale w/ large g-b subterm anchors, giving a checkered look; anchors may be larger and more solid, giving a scaled look usually mixed w/ adult gray; some w/o adult gray, appearing like a muddied version of 1W adult gray adult gray w/ white crescent about 1/3 bill length
BACK: dark anchors larger, making most of feather dark, giving scaled look adult gray mixed w/ g-b; some w/ little adult gray, looking pale and muddy adult gray adult gray is med light; darker than smithson, lighter than California
RUMP: heavily barred paler; lighter barring white white
TAIL: large broad dark band, contrasting w/ upperparts, w/ pale fringe, barred outermost webs and barred bases to outer few retrices gray tail band still darker than rest of back; bases of retrices whitish white w/ irreg broken subterm band white