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 sub-adult, August 10 2003, Etaples, France (50.44N, 01.35E).

Two images of feeding michahellis at Etaples. Average moult stage of the primaries in full adult birds: P8-P10 still old, P4 fully grown and P5 at the length of P3. Average Primary Moult Score (PMS) of adults: about 28 by August 10. All rectrices and secondaries old and present in the vast majority of full adult birds, showing heavy wear in the tail-feather tips.

The bird left in the pictures show advanced secondary and rectrices moult for michahellis. The outermost secondaries are shed, so secondary moult started at the division of primaries and secondaries. S1-S2 are just visible in the bottom image. Primary moult is slightly advanced as well, as P1-P5 are already fully grown and P9-P10 left. 
This advanced moult in remiges and rectrices, together with the brown-black markings on the greater primary coverts on the upper-wing might suggest sub-adultness, but the bird in the bottom image has no trace of black on the bill.