Mediterranean Gull (L. melanocephalus)
Mediterranean Gull 1cy HE31 August 25 2009, Le Portel / Boulogne-sur-Mer, NW France. Picture: Jean-Michel Sauvage.
Ringing data: ringed as pullus on 10 June 2009 at Bugyi (Kavics Union), Pest, Hungary (47N12'55"N 19E07'54"E). Distance: 1341 Km.
The complete juvenile plumage lasts for only a short period in Mediterranean Gulls as they start to moult soon after fledging. This post-juvenile moult is a partial moult into so-called "first winter" plumage that starts from the moment the birds leave their colonies in July and will be finished by late September. This moult includes most of the head and body feathers. The head and under-parts become almost completely white, with a dark mask of variable size and intensity behind the eye extending as very narrow streaks over the nape. The eye-crescents are white and the dark smudge in front of the eye contrasts more than in full juvenile plumage. The second generation wing-coverts, mantle and scapular feathers are plain pale grey. The rich brown centres of the juvenile wing-covert centres bleach to a foxy brown and the white fringes quickly wear away. In most birds at least some wing-coverts are included in the post-juvenile moult. The extent of this covert moult is variable, in a few birds nearly all are moulted, in others all juvenile coverts are retained until the next complete moult that starts in May of the next year. All juvenile feathers show wear by September, contrasting with the recently moulted second generation feathers. The base of the bill starts to turn paler and the legs turn slightly paler as well.
Note that the comments on moult are based on observations of juveniles from and in Western Europe. More easterly fledged Mediterranean Gulls may postpone their moult to first winter until later in the autumn and very fresh looking juveniles may be encountered well into October.