Atlantic Yellow-legged Gull (atlantis)

(last update: October 12, 2011)

Atlantic YLG 4cy January

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.

YELLOW-LEGGED GULL

LENGTH 21-26.3 IN. (53-67 CM)

IDENTIFICATION SUMMARY

This large yellow-legged gull is a casual visitor to e. N. America from Europe. Adult overall intermediate in appearance between Herring Gull and Lesser Black-backed Gull. Bill fairly stout and parallel edged (more so on nominate michahellis); gonydeal expansion varies from slight to moderate. Adult upperparts medium gray to pale slaty gray (Kodak 6-8.5; see Taxonomy) with fairly extensive black wing-tips (white mirrors on outer 1-2 primaries) and, in basic plumage, relatively limited dusky streaking mainly on head. ]uveni1e brown overall with contrasting white tail base and black distal tail band. Subsequent ages variable in appearance. First cycle has black bill, flesh legs become yellow by adult cycle; adult eyes pale lemon; orbital ring reddish. Breeding and molt cycles average 1-2 months earlier than American and European Herring Gulls.
Should be identified with great care in N. America, and note the potential of hybrid American Herring Gull x Lesser Black-backed Gull. L. m. atlantis suggests graellsii Lesser Black-backed Gull but slightly bulkier and broader winged; adult slightly paler above with underside of inner primaries and secondaries paler smoky gray; reduced dusky streaking on head and neck in basic. First-cycle atlantis also similar to graellsii but inner webs of inner primaries average paler, white tail base typically lacks distinct black barring at sides. Adult michahellis, by contrast, suggests American Herring Gull overall but upperparts slightly darker with more-extensive black wing-tips, duskier underside to remiges, reduced dusky streaking on head and hindneck in basic (often white headed by midwinter), yellowish legs, red orbital ring. First-cycle michahellis often suggests Great Black-backed Gull in its whitish head and underparts, boldly checkered and spangled upperparts. See Similar Species and Rarer Species sections for details.

TAXONOMY

Two widely recognized taxa in w. Europe: the smaller (21-24 in.; 53-61 cm), shorter-legged, and darker-backed (Kodak 7-8.5) atlantis of the Azores (Atlantic Yellow-legged Gull), which was once treated as a race of Lesser Black-backed Gull; and the larger (21.7-26.3 in.; 55-67 cm), longer-legged, and paler-backed (Kodak 6-7) nominate michahellis of the Mediterranean region (Mediterranean Yellow-legged Gull), which was once treated as a race of Herring Gull. Birds breeding along Atlantic coasts from nw. Spain to Morocco (including so-called Cantabrican Yellow-legged Gull in nw. Spain), and on the Canary Is. and Madeira may represent one or more unnamed taxa of Yellow-legged Gull. Pending more study of the complex, in the descriptions below we provisionally include Cantabrican birds with michahellis, and birds from the Canary Is. and Madeira with atlantis.
Yellow-legged Gull was considered conspecific with Herring Gull but now split by AOU and others as Larus cachinnans because of sympatry with limited interbreeding in France. But michahellis is very distinct from true cachinnans, and the two are best regarded as a separate species: Yellow-legged Gull L. michahellis and Caspian Gull L. cachinnans. The latter breeds in se. Europe and cen. Asia and seems an unlikely candidate for vagrancy to N. America.

STATUS AND DISTRIBUTION

S. Europe and islands off nw. Africa, including Azores. Casual nonbreeding visitor (mainly Oct./Dec.-Mar./Apr.; also June and Aug. records from Que.) to e. N. America from Atlantic Canada (mainly Nfld.) south to Mid-Atlantic coast, exceptionally Tex. (]an.-Apr. 2004). An Aug. specimen from Que. has been referred to Azorean L. m. atlantis; provenance of other birds uncertain.

CONTINUE PART 2: FIELD IDENTIFICATION