Atlantic Yellow-legged Gull (atlantis)

(last update: October 12, 2011)

Atlantic YLG 4cy March

Below you will find a description of YELLOW-LEGGED GULL (Larus michahellis), as published in one of the best Gull publication: "Gulls of the Americas" by Steve Howell & Jon Dunn.

"we" in the text below refers to the original authors. If any errors occur in this text, please let me know and mail to marsmuusseatgmaildotcom.

PART 1: HERE

PART 2: HERE

THIS IS PART 3:

HABITAT AND BEHAVIOR

Much as American Herring Gull, with which it is likely to be found in N. America.

DESCRIPTION AND MOLT

L. m. atlantis (breeds Atlantic Is.).

Adult Cycle.
Complete PB molt (May/June-Oct./Nov.) produces adult basic plumage: head, neck, and underparts white; head and neck with variable (often light) dusky streaking typically concentrated in half-hood and on lower hindneck; streaking most distinct during Aug.-Nov. and many birds mostly white headed in midwinter (Dec.-Feb.). Upperparts medium gray to pale slaty gray (Kodak 7-8.5, averaging paler on birds of Madeira and Canary Is.) with moderately extensive black wingtips (black on outer web of P10 and often P9 extends to primary coverts; P4 can have a small black mark), white scapular and tertial crescents; and white tips to outer primaries. Uppertail coverts and tail white. White trailing edge to secondaries (usually hidden at rest) and inner primaries breaks into discrete white tips on outer primaries; P5/P7 can show narrow whitish tongue-tips, P10 has distinct white mirror, and up to 20 percent of Azores adults (n = 30) have small P9 mirror. Underwings show black wingtips (with P10 or P9-P10 mirrors) demarcated from pale smoky gray, white-tipped inner primaries and secondaries, which form a dusky subterminal band on underwings. Eyes pale lemon, orbital ring red to orange-red. Bill yellow (often fairly bright) with large orange-red to red gonydeal spot (that often bleeds slightly onto maxilla), and sometimes dark distal marks. Legs yellow to flesh-yellow. Partial PA molt (Sept./Oct.-Feb./Mar.) produces adult alternate plumage: head and neck clean white (usually by Jan./Feb.); white primary tips reduced through wear. Orbital ring red, legs brighter yellow. Bill bright yellow with orange-red gonydeal spot, loses any dark distal marks, and orange-red gape more prominent.

First Cycle.
Juvenile (July/Aug.-]an.): dark brown to medium gray-brown overall. Head, neck, and underparts whitish, variably streaked and mottled gray-brown, becoming white on vent and undertail coverts, which have variable dark barring. Upperparts with buff (bleaching to dull whitish) scaly and notched edgings and markings, the outer greater coverts typically with rather plain, dark bases. Tertials blackish brown with notched whitish tips and distal edging. Uppertail coverts white with sparse dark markings. Remiges blackish with narrow whitish tips to secondaries and inner primaries; outer primaries with fine paler tips visible at rest (lost through wear), inner primaries with slightly paler inner webs forming indistinct paler panel on spread upperwing. Tail base white with sparse blackish markings, sharply demarcated from broad black distal tail band; outer web of R6 ribbed to edged white and tail narrowly tipped white.
IN FLIGHT: dark brownish overall with blackish flight feathers, indistinct paler panel on inner primaries, dark bar on greater-covert bases, and contrasting white uppertail coverts and tail base; underwings medium to dark brown. Eyes dark; blackish bill can show dull brownish base and fine pale tip by late winter; legs dusky flesh to flesh pink. PA1 molt (Sept.-Apr.; can include upperwing coverts) produces first alternate plumage: head, neck, and chest often bleach to mostly whitish with variable dusky brown streaking and spotting; A1 scapulars and upperwing coverts range from pale brownish with dark anchor marks, and dark brownish with broad paler edgings (earlier-molted feathers) to mostly grayish, often with dark shaft streaks (later-molted feathers). Eyes brown, orbital ring dull-flesh in summer. Bill black with variable dull-flesh basally in first summer and often a pale horn tip; legs flesh pink.

Second Cycle.
Complete PB2 molt (Apr./May-Sept./Oct.) into second basic plumage. Head, neck, and underparts whitish with variable dusky streaking and mottling typically heaviest at half-hood and on belly. Upperparts dark brown with paler edgings and sometimes a mix of gray back feathers; upperwing coverts less uniformly marked than first cycle, and tertials often with broader whitish edging and notching; uppertail coverts mostly white. Remiges similar to first cycle but averages a wider white trailing edge to secondaries and paler inner primaries, which usually form an indistinct paler panel; tail ranges from extensively black to variably mixed with white; base less neatly marked than first cycle. Underwings dark with paler inner primaries when backlit. Eyes brownish to dirty pale lemon; bill typically flesh basally, black distally with a pale horn tip, legs flesh pink to yellowish flesh. Partial PA2 molt (Sept.-Mar./Apr.; often includes some upperwing coverts) produces second alternate plumage: head, neck, and underparts white, variably streaked and mottled dusky (often bleaching and wearing to mostly white by summer), back typically becomes mostly pale slaty gray in contrast to faded upperwing coverts; some birds attain a few plain gray upperwing coverts, especially median coverts. Eyes pale lemon to dusky, orbital ring reddish in summer. Through winter, bill typically pinkish basally, blackish distally with a pale tip and sometimes a blush of red at gonys; in summer, bill typically yellow with reddish gonydeal smudge and black distal band. Legs yellowish.

Third Cycle.
Complete PB3 molt (May/June-Oct./Nov.) produces third basic plumage. Some “retarded” plumages resemble second cycle but with more gray on upperparts, less black in tail. More advanced-looking plumages typical, and variably resemble basic adult but with heavier dusky streaking and spotting on head and neck, typically forming a grayish streaked hood; upperwing coverts may be washed brownish; tertials can show dark centers; white tips to remiges narrower. Tail often all white but some have blackish distal markings. Blackish wingtip pattern averages more extensive and browner, with less white than adult; variable blackish on primary coverts and alula; P9 typically lacks mirror, and P10 mirror smaller to absent. Underwings have some dusky mottling on coverts. Eyes pale lemon; bill flesh pink with variable black median band and markings, and pale tip, often with some reddish at gonys; legs yellow to yellowish flesh. Partial PA3 molt (Sept.-Feb./Mar.) into third alternate plumage: dark markings on head and neck reduced to absent; bill brighter and often indistinguishable from adult or with faint dark distal marks. White tips to outer primaries often lost by wear. Adult plumage attained by complete PB4 molt (May/June-Oct./Nov.).

L. m. michahellis (breeds Mediterranean region).

Upperparts of adults and older immatures paler, medium gray (Kodak 6-7). Mediterranean birds larger, longer-legged, and bulkier overall than atlantis with stouter bill and earlier molt timing; but some mainland Atlantic Coast birds more similar in structure to atlantis; Cantabrican birds of nw. Spain look somewhat intermediate between Mediterranean Yellow-legged Gull and European Herring Gull.

Adult Cycle.
Complete PB molt (May-Sept./Nov.) produces adult basic plumage. Similar to atlantis but upperparts paler, medium gray, averages less-extensive dusky head streaking, eyes average darker yellow. Bare parts similar to atlantis. Basic head streaking on Mediterranean birds most distinct during Aug.-Oct.; most become white headed by Nov.-Dec.; Cantabrican birds average later molt and more-extensive dusky streaking in basic (extending down hindneck), often retained through Jan.

First Cycle.
Juvenile (July-Sept./Oct.): similar to atlantis but head, neck, and underparts whiter, often bleaching to whitish by Sept.; inner primary panel averages paler on upperwing. PA1 more rapid and averages more extensive (late July-Mar./Apr.), often including numerous upperwing coverts and even tertials by Sept./Oct.; but Cantabrican birds molt later and often replace no upperwing coverts. Al scapulars typically pale grayish with dark anchor marks or broad subterminal bars.

Second Cycle.
Complete PB2 molt (Apr.-Aug./Sept.) and partial PA2 (Sept.-Mar.). Basic head, neck, and underparts whiter overall than atlantis, new gray feathers in back average paler, medium gray, and inner primary panel on upperwing slightly more distinct.

Third Cycle.
Differs from atlantis in same respects as does adult michahellis.

HYBRID

Has bred with Lesser Black-backed Gull and European Herring Gull in w. Europe, Kelp Gull in Mauritania, and presumably with Caspian Gull (L. cachinnans) in Po1and.

NOTES

1. Dwight 1925;
2. Cramp and Simmons 1983;
3. Dubois 2001;
4. Dubois and Yésou 1984;
5. Yésou 2002;
6. Cramp and Simmons 1983;
7. AOU 1998; 8. Yésou 1991;
9. Crochet et al. 2002;
10. de Knijff et al. 2001;
11. Klein and Buchheim 1997;
12. Liebers et al. 2001;
13. ABA 2002;
14. Wilds and Czaplak 1994;
15. Harris et al. 1978;
16. N. T. Elliott pers. comm.;
17. A. Bermejo pers. comm.;
18. Malling Olsen and Larsson 2003;
19. Howell pers. obs.;
20. Dubois 2001;
21. Howell pers. obs.;
22. A. Bermejo pers. comm.;
23. Ibid.;
24. Cottaar 2004;
25. Garner 1997;
26. Yésou 1991;
27. Pineau et al. 2001;
28. Faber et al. 2001