L. michahellis: 1cy August

General description:

Yellow-legged Gulls L.michahellis, which breed in southern Europe / the Mediterranean have a significant earlier breeding season than the large gulls breeding in western and northern Europe, Herring Gulls (HG) argenteus & argentatus and Lesser Black-backed Gulls (LBBG) graellsii & intermedius). As a result, most juvenile YLG's show more worn plumages than northern relatives by August (on average). Geographical latitude of breeding grounds probably is the main reason for these differences in feather conditions, but there may be many other aspects involved as well, like e.g. exposure to severe summer light condition.

Subsequently, the average moult timing to 1^st winter plumage commences earlier in the season (from late July-early August) than in LBBG and HG. By late August, almost all michahellis in the Calais Region, NW France already moult in second generation feathers. The mantle, scapulars and sometimes median covert, a few lesser coverts and tertials are involved. 
Herring Gulls with abraded fringes in the coverts and the same moult stage as michahellis are extremely rare, but some Lesser Black-backed Gulls also acquire new wing-coverts as early as August. However, in most cases the condition of the old feathers is different: michahellis have retarded feathers (the fringes of the feathers more abraded), while in graellsii the coverts are generally fresher. Of course it's interesting to find out how southern populations of graellsii adapt or change the egg-laying date in the near future now they expand their breeding area in France and further south.

Wing-covert moult in michahellis

The moult of the wing-coverts in michahellis may start in late July in a few individuals (see for details the tables presented in the July section). In the last week of August we scored moult stage in Boulogne-sur-Mer (NW France) in a group of 22 first calendar year (1cy) michahellis: 4 individuals (18%) had started the wing-covert moult (involving the median and lesser coverts). Late August, the most advanced individual showed c. 80% renewed median and greater coverts. Approximately 20% of the lesser coverts were moulted and the upper three tertials were missing. 

Most michahellis start moulting the wing-coverts in September and throughout the winter months wing-covert moult continues. About 80% of 1^st winter michahellis will show at least some moulted wing-coverts in spring next season (by then in 2cy).
The first birds with a 90-100% wing-covert moult score (all visible wing coverts replaced by second generation feathers) can be found as early as September. We have limited experience with "late winter covert score" (by then 2cy michahellis in spring), but we estimate less than 10% of michahellis to show all the visible coverts new. Probably, at least some wing-coverts will not be shed in 1^st winter and remain juvenile feathers until spring next season, when the complete moult-cyclus starts.

Table

Photo 21: michahellis 1cy August 12 2006, IJmuiden, the Netherlands.