delawarensis Ring-billed Gull

(last update: 10-03-2014 )

Coordinators:
Keith Mueller
Amar Ayyash
Mars Muusse

Index ORG

ring projects
PDF's

1cy June
1cy July
1cy Aug
1cy Sept
1cy Oct
1cy Nov
1cy Dec

2cy Jan
2cy Feb
2cy March
2cy April
2cy May
2cy June
2cy July
2cy Aug
2cy Sept
2cy Oct
2cy Nov
2cy Dec

3cy Jan
3cy Feb
3cy March
3cy April
3cy May
3cy June
3cy July
3cy Aug
3cy Sept

adult Jan
adult Feb
adult March
adult April
adult May
adult June
adult July
adult Aug
adult Sept
adult Oct
adult Nov
adult Dec

1st cycle (2CY): April

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
part 2: IDENTIFICATION of JUVENILE
part 3: IDENTIFICATION of 1ST SUMMER - 3RD WINTER

below part 4: VOICE, MOULT & DESCRIPTION ADULT

VOICE
Calls deeper, less mewing than in Common Gull: a mellow kowk. More similar to Herring Gull, but higher-pitched; intermediate between Herring and Common Gull. Advertising call 2-4 short notes followed by a series of 5-7 hoarser calls, slightly penetrating in the middle (Glutz von Blotzheim & Bauer 1982, Urban et al. 1986).

MOULT
(pers. obs. USA, photos and skins) Adult moult to winter plumage is complete May-Oct. P1 late May/ early June; P7-8(9) Aug, P9-10 late Sep-mid-Oct (Nov). Head and body Aug-early Sep. Moult to adult summer plumage partial Mar-Apr, including head and body. Many still in winter plumage early Mar, the majority in summer plumage mid-Apr. juvenile moult to first-winter plumage partial Aug-Sep, including all or most of head and underparts, mantle, much of back and rump, most of scapulars and sometimes a few median coverts. Some in juvenile plumage into Nov (Lauro & Spencer 1980). Moult to first-summer is first stages to complete moult into second-winter ((Mar)May-Oct) includes head, body and some wing-coverts (especially median and inner greater coverts). Tertials from May. Often retains some juvenile scapulars until first-summer. Occasionally T1-2 renewed; a bird from Mar had three new rectrices on one side of the tail. This moult could alternatively be regarded as the first part of the complete moult into second-winter. Moult to second-winter complete May-Oct. P1 from May, on average a month earlier than in Common Gull; reaches P5 late June; P7-8 early Aug; P8-P10 late Aug-mid-Sep; primary moult usually completed late Sep (compare adult). Body, coverts and tertials from May; may retain few juvenile coverts to Oct. Secondaries and tail June-July (Mjos & Solheim 1995), sometimes not before late July, but most in heavy tail moult June (T1-2,6), completing early Sep. Moult to second-summer partial Feb—May, including head and body. Generally later than in adult; some still have winter head mid-Apr. Moult to third-winter complete June-Oct; similar to adult.

Ring-billed Gull delawarensis 0734-24852 adult, August 25 2012, Rainbow Beach - Chicago, IL. (Amar Ayyash).	Ring-billed Gull delawarensis 0734-24852 adult, September 15 2012, Rainbow Beach - Chicago, IL. (Amar Ayyash).
Moult timing Adult male, Fed Band number: 0734-24852. Banded as adult (hatched <2007) on November 05 2007 at Chicago, IL, USA. Adult Ring-billed Gulls typically complete their prebasic molts by the end of October. Here's a series of photos documenting primary growth of a known-age RBGU taken at Rainbow Beach in Chicago, Illinois.
Ring-billed Gull delawarensis 0734-24852 adult, October 06 2012, Rainbow Beach - Chicago, IL. (Amar Ayyash).	Ring-billed Gull delawarensis 0734-24852 adult, October 26 2012, Rainbow Beach - Chicago, IL. (Amar Ayyash).

DESCRIPTION

Adult
Head, underparts, underwing-coverts and tail white. Upperparts and upperwing pale grey (Kodak Grey Scale 3-4(5)). Primary pattern similar to Common Gull nominate canus, but white mirrors on P9-P10 smaller - 22-42 mm on P10, extending over both webs but with large black tip (in Common almost reaching tip of feather 8-22 mm on P9, frequently narrow oval-shaped spot only on inner web). White mirror on P9 increases in size with age. P6 with 12-40 mm black sub-terminal spot, P5 with small dark subterminal spot on both webs (sometimes lacking). P10 5-7rnm >P9. Normally just with inconspicuous white ‘moons’ between black tips and grey bases of primaries (sometimes lacking; rarely as distinct as in Common and Mew Gulls). Tips to P1-7, secondaries and tertials white; less contrasting than in Common, as division is weaker and narrower, and upperparts paler.

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

below: Ring-billed Gull delawarensis adult, March 03 2014, Appalachians, Ohio (Roger Hickey).

Adult summer (Mar-Sep/ Oct)
Head white. With wear, white primary tips reduced or lacking. Orbital ring red to orange-red. Iris pale yellow. Bill bright yellow to orange-yellow with 5-10 mm clear-cut black ring of even width on both mandibles (rarely reduced to dark subterminal spots, especially in late breeding season). Bill-base often greenish-tinged, tip sometimes paler ivory. Gape orange. Legs bright yellow to greenish-yellow.

Adult winter (Aug/ Sep-Mar/ Apr)
Head with dark spots, strongest on hindneck, nape and around eye, sometimes extending onto lower throat, sides of breast and upper flanks as narrower spots or scales. Crown often with narrow brown streaks. Often shows white ‘half-moon’ on lower ear-coverts contrasting with dark-spotted upper ear-coverts and hindneck. White eyelids broad, contrasting with grey around eye (more so than in Common Gull; most evident in lower eye-crescent and from mid-eye level and behind). Bill and legs duller yellow than in adult summer; bill-base often greyish- or greenish-tinged, tip sometimes ivory. Bill-ring 9-12 mm. Orbital ring blackish.

above: Ring-billed Gull delawarensis adult, December 20 2007, Martin Co., FL. (John Avise).
below: Ring-billed Gull delawarensis adult, January 01 2013, Scarborough Beach, RI. (Keith Mueller).

CONTINUE PART 5: DESCRIPTION JUVENILE - 2ND SUMMER