August is one of the best months to study michahellis
at Le Portel and Etaples, NW France. At the beach of Le Touquet, near
Etaples, large groups congregate and use the beach as a resting place.
They frequent the Dannes landfill as feeding place and many depend on the
local fish-market of Etaples for food supply. The ports of
Boulogne-sur-Mer and the beach of Le Portel are other good spots to find
sub-adult Yellow-legged Gulls. See Le
page for locations.
The difference between 3cy birds and 4cy
birds can best be checked by the outer primary, which may still
be unshed by August: 4cy birds show a small but obvious white mirror on
P10, while 3cy birds have the (second generation) outer primary all
brown. Other clues can be found in the bare part coloration, with
4cy strongly resembling adults. Sub-adult michahellis has
black in the old outer primary coverts and dark centres on the old
secondaries. Furthermore, 3cy birds often have one or several second
generation tail-feathers, showing a broad black band.
moult in August:
As can be seen in most of the images,
sub-adult Yellow-legged Gulls look very untidy and mottled in their
August plumage, as was already the case in July. Simultaneous moult is in progress in the primaries,
wing-coverts, tertials, scapulars and the
By August, the median row and outer lower lesser coverts have been
renewed already a month ago. The inner greater coverts and upper
tertials have been replaced as well. Active moult is in progress in
the outer greater coverts (growing inwards, in descendant order) and
in the lesser coverts. The lower tertials are growing as well.
By the end of the month, the central greater coverts are still
missing and many lesser coverts are missing as well. In the carpal
edge, coverts may still be old and abraded.
The fresh grey median coverts
normally strongly contrast with the brown-hued and abraded lesser coverts and
old greater coverts (some central greater coverts are still present
by early August).
stage and pace of remiges and rectrices:
Currently, we don't have sufficient
data for detailed moult descriptions of sub-adult August birds. But
in general, the primary moult stage of sub-adult birds averages P8-P10
remaining primaries in the first week of August. By this time, the new central
tail-feathers are growing and the average bird has dropped the outermost
Section for explanation of feather tracts.
7338: michahellis sub-adult,
August 10 2003, Etaples, France.