delawarensis Ring-billed Gull

(last update: 10-03-2014 )

Coordinators:
Keith Mueller
Amar Ayyash
Mars Muusse

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1st cycle (2CY): January

Ring-billed Gull - Larus delawarensis. Description in "Gulls of North America, Europe, and Asia", by Klaus Malling Olsen & Hans Larsson, Princeton University Press.

This is a copy of the chapter on Ring-billed Gull, written by Klaus Malling Olsen. "I" in the text refer to the author. If you find any errors, please let me know at marsmuusse at gmail dot com.

Ring-billed Gull - Larus delawarensis

part 1: IDENTIFICATION of ADULT

IDENTIFICATION
Length 43-47 cm, wingspan 120-155 cm. Ring-billed Gull is similar to Common Gull and Mew Gull, but on average larger and bulkier with thicker, more parallel-edged (i.e. untapering) bill. Compared to Common, the head is squarer with a flatter crown, fuller neck and more distinct peak behind the eye. The gape is generally longer and more down-curved, often penetrating to below the eye creating an angry look. Deeper breast and longer legs may give a plover-like impression combined with ‘free and easy’ gait. The heavier-billed birds (males) have bill longer than the distance from the bill-base to the eye (longer than any Common Gull) and look - especially the pale-eyed adults - like miniature large gulls. Importantly, upperparts are much paler grey than in Common and Mew Gull - similar to Black-headed, Herring race argenteus, American Herring or even Glaucous Gull. Flight is lighter than Herring, but heavier than Common Gull. Wings proportionately longer than in Common Gull, with a broader arm. Although large males, with their square head and broad neck as well as rather heavy, parallel-edged bill, are much more large-gull-like than any Common Gull (and certainly Mew), small females may appear round-headed with rather narrow bills. In such birds, bill-shape is still important, being parallel-edged rather than (normally) broader at the base than on the rest of the bill even in heavy-billed Common. Note that Common Gull race kamtschatschensis is closest in size to Ring-billed Gull, but jizz-wise is still a Common Gull. Grey feathers that appear on upperparts of Ring-billed are much paler than on any Common or Mew Gull.

Ring-billed Gull delawarensis adult, April 2007, Toronto, Ontario, Canada (Wikipedia).

Ring-billed Gull delawarensis adult, January 09 2011, Jekyll Island Georgia (Larry Gridley).	Common Gull canus SVS 7187947 adult, January 19 2014, Stella-Plage / Boulogne, France (Jean-Michel Sauvage).
Ring-billed Gull delawarensis adult, February 07 2009, New York (Dick Daniels).	Common Gull canus DEH IA 052611 12CY, February 02 2013, Calais, France (Jean-Michel Sauvage).
Ring-billed Gull delawarensis adult, March 01 2013, Canaveral National Seashore, FL. (Tammy Karr).	Common Gull canus DEH IA 057572 10CY, December 10 2011, Le-Touquet / Boulogne, France (Jean-Michel Sauvage).
Ring-billed Gull delawarensis adult, March 01 2013, Canaveral National Seashore, FL. (Tammy Karr).	Common Gull heinei adult, January 2010, Copenhagen, Denmark (Kjeld Tommy Pedersen).
Ring-billed Gull delawarensis adult, March 17 2013, Rio Grande, NJ. (Don Freiday).	Mew Gull brachyrhynchus adult, January 27 2010, Luther Burbank Park, Mercer Is., WA. (Dennis Cheasebro).
Ring-billed Gull delawarensis adult, April 10 2012, Quidi Vidi, Newfoundland (Lisa de Leon).	Mew Gull brachyrhynchus adult, June 14 2012, Denali NP, Alaska (Glenda Suebee).
Ring-billed Gull delawarensis AAH adult, December 07 2011 & January 13 2013, Hammonasset Beach SP, Madison, CT. Picture: Keith Mueller.	Common Gull kamtschatschensis adult, February 21 2010, Choshi, Japan (Goodhilda).

Adult
Has pale yellow eyes (surrounded by dark orbital ring) and a yellow bill with a full clear-cut black ring, evident even at distances when the pale eyes are hard to judge (dark orbital ring tends to ‘obscure’ pallor of eyes at longer ranges). The bill ring is normally broader (than the width of the eye. The upperparts are pale grey and show only diffuse white tertial and rear scapular crescents and trailing edge to the inner wing. Mantle often a tinge darker than primary bases. Wing-tip similar to Herring race argenteus, with small white mirror on
P10 (smaller than in Common Gull, with a larger black tip). Bare parts yellow, especially in summer brighter yellow than in Common Gull. Settled adults combine ‘smal1 Herring-Gull head’ with overall shape of Common Gull, including long wing projection behind tail. In summer, head white and orbital ring orange to red. In winter, head dark-spotted, typically darker and more densely spotted than in Common or Mew Gulls, strongest on hindneck and around eyes. Neck-sides often white, sometimes strikingly so. Orbital ring blackish, like black glasses around the pale eyes.

Common and Mew Gulls have darker grey upperparts with a much more distinct white tertial crescents and trailing edge to the inner wing (the former mainly a character in settled birds). Their eyes are dark or darkish-looking, appearing large on the rounded head (Mew and Common race kamtschatschensis regularly show pale eyes, but never as whitish-yellow as Ring-billed). If present, bill-ring in Common and (especially) Mew is narrow, often irregular in form of Z-shaped bar, appearing narrower than the width of the eye. White mirrors on outer primaries are larger, appearing as a rounded white spot, and white ‘moons’ on the mid-primaries are conspicuous (lacking or just faint in Ring-billed). California Gull is larger with a longer, often four-coloured bill (red, yellow, black and ivory), dark eyes, and variable leg colour, generally with a greyer or greener tinge than in Ring-billed.

Ring-billed Gull delawarensis KPL adult, February 19 2011, Plymouth, MA. (J. Trimble).	Common Gull canus AV86 adult, February 02 2014, Riga, Letland ( Igor Denisov).
Ring-billed Gull delawarensis adult, October 26 2010, Québec City, Québec (Guy Poisson).	Common Gull canus DEH IA 052611 12CY, February 09 2013, Calais, France (Jean-Michel Sauvage).
Ring-billed Gull delawarensis 440 adult, March 01 2010, Print Works Pond, Cranston, RI. (Scott Grant).	Mew Gull brachyrhynchus adult, October 10 2008, Richmond, BC. (Punk Birder).
Ring-billed Gull delawarensis blue tag adult, October 26 2012, Rainbow Beach - Chicago, IL. (Amar Ayyash).	Mew Gull brachyrhynchus adult, January 03 2012, Sayer's Park, Lake Washington (Amar Ayyash).
Ring-billed Gull delawarensis adult, April 02 2010, Newfoundland, Canada ( Lisa de Leon).	Mew Gull brachyrhynchus adult, February 24 2007, Santa Ana River mouth, Orange Co., CA. (John Avise).
Ring-billed Gull delawarensis adult, November 13 2011, New Jersey (Paul A. Guris).	Mew Gull brachyrhynchus adult, December 18 2013, Radio Road ponds. Redwood City, San Mateo Co., CA. (Ron Wolf).
Ring-billed Gull delawarensis adult, February 22 2012, Virginia Lake, Reno, Washoe Co, Nevada (Fugle).	Common Gull kamtschatschensis adult, March 13 2010, Choshi, Japan (Goodhilda).

CONTINUE PART 2: IDENTIFICATION of JUVENILE