Yellow-legged Gull - Larus michahellis

(last update: October 08 2013)

Delfín González
Gabriel Martín
Antonio Gutierrez
Amir Ben Dov
Mars Muusse

Yellow-legged Gull michahellis 662D 3CY, June 28 2003, Etaples, France (50.42N,1.34E).

3CY michahellis with P8-P10 still old by late June. 662D has pale yellow legs, a clear yellow bill with a small red spot and limited black, just creating a bill-band. The iris is yellow and the orbital ring is red. The mantle and scapular region is completely grey. The upper tertial has been shed, while outer median and inner greater coverts are fresh, adult-like grey, contrasting with the old second generation brown barred central greater and lesser coverts.

The tail is complete and all rectrices are second generation. The primary moult stage is P8 old, P7 missing. By mid-June, several 3CY michahellis were observed with primary moult score P3 missing / P4 old or with P4 missing / P5 old. By late June, the average primary score of old primaries is 4.5. 3CY birds are on average 1.8 primaries behind compared with 2CY birds. 

Primary moult score in 3CY Larus michahellis, Etaples, NW France on June 28 2003 (09:00 h, low tide).
. P2 fg P3 fg P4 fg P5 fg ? fg n:
P5-P10 1 - - - 6 7
P6-P10 - 3 - - 34 37
P7-P10 - 4 3 1 27 35
P8-P10 - - 1 2 2 5
n: 1 7 4 3 69 84
n = 84; m old P = 4.5; SD old P = 0.73.
Group: 3x 3CY michahellis not scored; total michahellis present: 300+.
P6-P10 = P6-P10 are still old and present.
? fg = fully grown not known. Often referring to sleeping birds with folded wings, so fully grown primary score most probably P6 or less.
fg = fully grown. In our field surveys, a primary is 'fully grown' when it exceeds the previous feather in the folded wing. Actually,  such 'fully grown' feathers may have to grow a little, but under field circumstances, it's very difficult to find out if the waxy sheath, which is the standard measurement for fully grown primaries, is still present. 
3CY identified on absence of P10 mirror & bare parts coloration.