L. michahellis: 1cy December
By December, 1cy michahellis shows more or
less the same moult stage as birds from November. Active moult is nearly
completely suspended now winter starts. Remarkably,
in mid winter, the majority of michahellis from SW Netherlands and
Le Portel (NW France) still show completely juvenile wing-coverts (but
sample size is insufficient to draw any conclusions). This
contradicts with the figures from July - September, so different
individuals (and even different populations?) may be involved throughout
the months. On some locations in the Netherlands, like landfills, inland gravel pits
along the river Meuse and along the coast (like the Maasvlakte, near the
port of Rotterdam) small groups can be found daily.
Identification of 1cy Yellow-legged Gull
is rather straightforward in birds with moulted wing-coverts and tertials,
although some 1cy cachinnans may look pretty similar, especially
when males are involved. To compare these plumages, have a look at the 1cy cachinnans section. Yellow-legged Gull has extensive moult
in the under-parts by December, with the second generation head already
turning white in some individuals. The 1cy partial moult (post-juvenile
moult) in the under-parts includes the head, neck, breast, belly and
flanks. The under-tail coverts are normally excluded from this partial
The mantle and scapulars consist of second generation feathers, which are
slightly worn at the fringes in the upper scapular region. These feathers
were moulted late July and in August, hence are already more than four
months old. In the lowest row of the scapulars, the recently moulted
feathers have a neat fringe but the buffish hue on the centres start to
fade away. In some 1cy michahellis, the next moult in the upper scapulars
takes place, with feathers now replaced for the second time: moult to
Normally, best clues for 1cy michahellis:
- strong and powerful bird. Strong
breast, large bird, especially males.
- heavy bill with an obvious gonydeal
- angular head with sloped forehead.
- advanced moult stage in under-parts
- ill-defined window on the inner
primaries confined to the inner-webs of the primaries.
- wedge-shaped tail-band, narrow on the
outer rectrices (R6), where almost completely reduced to the inner-web
- dark outer greater coverts with the
white fringe not reaching the base of the feather on the outermost
Moult stage and
All 1cy michahellis have shed
and replaced the juvenile feathers in the scapulars and mantle feathers.
In turn the mantle and scapulars feathers are completely second
generation. The ordinary pattern is a pale based centre with dark
bars or an anchor pattern.
The covert and tertial moult vary to a large extend at Etaples, with a
remarkable high proportion of birds in January showing all the
wing-coverts and tertials still juvenile (remarkable higher numbers than
expected on the figures from October, where only 19-27% of the 1cy birds
had all the wing-coverts and tertials juvenile). Year 2002, more research
at this location has to be executed to confirm the first findings. An
example of a bird with all the wing-coverts and tertials still juvenile
can be seen in image 7990.
birds have various amount of replaced feathers in wing-coverts and
tertials (as can be seen in image 7963).
Limited data on moult doesn't allow us to draw any conclusions on the average
1cy michahellis moult stage by mid December.
| michahellis 1cy U1KF December 17 2010, Tel Aviv - University Garden, Israel. Picture: Amir Ben Dov.