third calendar year: January - April
During
April only the very first of 3cy birds return to the colony. The first
arrive around mid-April, the majority around mid-May in the Netherlands. They join the
adults arriving as early as possible to find the best breeding spots in
last years colonies. The counted maximum number of 3cy’s estimates 100
(mid-May),
on the total of 1.500 LBBG present at the Maasvlakte, the Netherlands.
Higher numbers can be found on the wintering grounds (Portuguese coast and
in S France) or at the stop-over places (e.g. Pas-de Calais).
moult
stage
in typical 3cy LBBG:
It is important to distinguish between 'typical' 3cy LBBG and advanced birds. The activity in moult during April is virtually zero in typical LBBG, what has long been considered typical graellsii. In these typical birds, there has been no moult on the wintering grounds and returning 3cy birds in spring show more or less the same plumage as the plumage of 2cy October birds. They have a worn second generation tail, i.e. a tail with a black, broad sub-terminal tail-band, which has been required last autumn in the complete moult. Some birds will start or have started moulting some of the tail-feathers by April. The primaries are slightly worn at the tips, but still all second generation.
Otherwise, these typical 3cy birds still show brownish second generation
wing-coverts (greaters and lessers at least) while upper-parts and bare
parts look very adult-like, resulting in the well-known "grey
saddle" in 3cy LBBG in spring.
moult
in advanced
3cy LBBG:
By April, groups of 3cy LBBG increasingly include advanced birds,
most obvious advanced in the upper-parts and wing-coverts. It's not
uncommon to find 3cy LBBG with recently replaced wing-coverts in April,
indicating that these feathers have been replaced on the wintering
grounds, during the last months. Such birds may show complete adult-like
upper-parts and the dark grey-tone of the new scapulars and coverts
suggest they may origin from intermedius colonies. However, they
may also return in Dutch colonies, as image
283 shows. It is worth checking the tail, secondaries and
primaries in such birds, as advanced partial moult in the upper-parts may
correlate with moult in these tracts as well.
tail-feather
& primary
moult in advanced LBBG:
Most
commonly seen at this age now, is a worn second generation tail. But
remember that quite some 2cy LBBG return in NW Europe with second
generation tail-feathers in spring, and renew these tail-feathers in a
second wave in the complete summer moult. Consequently, such birds may
already show an almost complete white tail by October in second calendar
year (see here).
Therefore, it is possible that 2cy LBBG leave NW Europe with already a
white tail and show white tails in spring again.
3cy
LBBG in spring may include tail-feathers in the partial spring moult
again, and may still be actively replacing rectrices in April (see e.g. image
8861). About 30% of the 3cy LBBG have moulted one or more tail feathers
by the end og April, giving them the blocked pattern of white (third or
fourth generation feathers) and partial black tail-feathers. The partial moult involves rectrices randomly,
creating an unpredictable black and white tail in spring.
At
the end of April only the very advanced birds have started the complete
moult and have shed P1. The ordinary moult-sequence of the secondaries
start when P6 is almost fully grown, by mid-summer. But here again,
primaries and secondaries may be included in the partial moult on the
wintering grounds. Image 283 nicely
illustrates arrested primary moult in spring 3cy LBBG. On the wintering
grounds, partial moult must have been very extensive in the upper-parts,
as almost all wing-coverts are very adult-like. In this extensive moult,
the inner primaries were moulted as well, just as most of the
tail-feathers.
In
this respect, the western taxa intermedius and graellsii
LBBG may resemble eastern fuscus., which very commonly replaced
remiges and rectrices on the wintering grounds.
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