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 2CY, September 21 2002, Etaples / Boulogne-sur-Mer, NW France.

A boldly patterned 2CY michahellis with the scapulars replaced for adult-like grey feathers. The head and under-parts have been moulted. Primary P10 is slightly shorter than P9, resulting in a primary moult score (PMS) of 49. See Gull Topography for explanation of PMS.
The partial moult in autumn is well underway with the upper tertial been replaced for at least third generation feather with barred pattern. The exact generation is difficult to proof when dealing with unringed birds which have not been followed over the last two years. As can be seen in several 1CY sections, many michahellis include upper tertials in the post-juvenile (first pre-basic) moult, so the moult in 2CY autumn birds may result in new upper tertials of fourth generation.
The second tertial is missing and will be replaced as well this autumn. The lower four tertials are still one generation older, either second or third generation feathers. As can be seen in the 1CY sections, not many birds include all tertials in the post-juvenile moult, so the majority of 2CY michahellis have second generation lower tertials (only moulted once during the complete moult last summer).
The second greater covert is included in the partial moult as well. Most obvious moult is going on in the median coverts with the complete central row missing and growing. In the lower lesser coverts one feather is new and one is missing. The lesser coverts were very recently replaced in the complete moult, which finishes by August, and in this individual, the lessers are excluded from the partial moult in autumn so far.