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 242T 3CY, June 28 2003, Etaples, France (50.42N,1.34E).

3CY michahellis with P6-P10 still old by late June. 242T has pale yellow legs, a clear yellow bill with a small red spot and limited black. The iris is dark yellow and the orbital ring is red. The mantle and scapular region is almost completely grey. The upper tertials, median and inner greater coverts are more adult-like than the brown barred central greater and lesser coverts. This bird was ringed near Marseille, S France, probably in year 2000. When data are available, more information will be added.

Most grey feathers in the wing-coverts are in better condition than the barred feathers, and apparently were moulted later, i.e. in the partial autumn moult in 2CY (September-October). The inner greater coverts, the inner medians, a few lower lesser and some lesser coverts appear plain grey. The upper tertials are at least third generation as well, maybe even fourth generation, depending on the extend of the partial post-juvenile moult and the partial autumn moult as 2CY.

The tail is complete and all rectrices are second generation. The primary moult stage is P6 old, P5 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.