first
calendar year: September
Last update of
this page: 26-10-03 17:33
Last year we did a small survey on juvenile
LBBG and moult (n=45). This year the survey was repeated and was done
inside the colony in August. For the results, see the Juvenile LBBG August
Section.
By September, the large majority of
juvenile LBBG have left the Netherlands and must have moved south towards
Portugal. Many of the Dutch juveniles, which were seen moulting the
scapulars in the colony (in August) must have joined these migrating
groups. Nevertheless, many juveniles can still be found in the
Netherlands, but as September progresses, more juveniles from Scandinavian
colonies move in. This may be a reason for the "observed
stand-still" in moult progress in juveniles: those local juveniles
with advanced moult move south and less advanced individuals from
Scandinavia fill the open positions or gather in mixed local groups.
Best option to reduce this problem is
simultaneous counts throughout the West European coastline, or counts
which only involve ringed individuals (thus from certain origin).
The problem of later hatched intermedius, moving into early
moulting graellsii-groups is not a problem restricted to juveniles.
To get a clear picture about arrested primary moult in autumn in adult graellsii
plumage, the best place to look for these adults is probably outside the
Netherlands, at the first major stop-over sites in Portugal for instance.
It is believed that particularly those adults, which arrest primary moult,
may also be keen on migrating south as quick as possible.
Moult score
in body feathers of juvenile LBBG 16.09.2000, Maasvlakte, the
Netherlands.
mantle =mantle + scapulars;
lesser =lesser coverts,
median =
median coverts,
greater = greater coverts,
# = number of
individuals.
Normal pattern: moult in lower neck, followed by
mantle, scapulars, coverts. First moulted coverts are the medians. |
mantle |
lesser |
median |
greater |
# |
0% |
0 |
0 |
0 |
23 |
10% |
0 |
0 |
0 |
3 |
30% |
0 |
0 |
0 |
2 |
40% |
0 |
0 |
0 |
2 |
50% |
0 |
0 |
0 |
1 |
50% |
0 |
1 |
0 |
1 |
50% |
0 |
3 |
3 |
1 |
60% |
0 |
2 |
2 |
1 |
70% |
0 |
0 |
0 |
2 |
70% |
0 |
2 |
0 |
1 |
75% |
0 |
1 |
0 |
2 |
80% |
0 |
2 |
1 |
1 |
80% |
0 |
2 |
6 |
1 |
90% |
0 |
3 |
3 |
1 |
100% |
0 |
1 |
0 |
1 |
100% |
1 |
6 |
1 |
1 |
100% |
3 |
4 |
1 |
1 |
n = 45 exx. |
|
LBBG juvenile
Click the thumbnail to find ringed LBBG's from September. |
Photo
1: LBBG juvenile, Dintelhaven Maasvlakte, the Netherlands, September
02
2001. |
Photo
2: LBBG juvenile, Brouwersdam, the Netherlands, September 02 2001. |
Photo
3: LBBG juvenile, Brouwersdam, the Netherlands, September 02 2001. |
Photo
4: LBBG juvenile, Boulogne-sur-Mer, NW France, September 22
2002. |
Photo
6: LBBG juvenile, Brouwersdam, the Netherlands, September 02 2001. |
Photo
7: LBBG juvenile, Brouwersdam, the Netherlands, September 02 2001. |
Photo
8: LBBG juvenile, Brouwersdam, the Netherlands, September 02 2001.
|
Photo
9: LBBG juvenile, Brouwersdam, the Netherlands, September 02 2001. |
Photo
10: LBBG juvenile, Brouwersdam, the Netherlands, September 02 2001. |
Photo
11: LBBG juvenile, Brouwersdam, the Netherlands, September 02 2001. |
Photo
12: LBBG juvenile, Dannes France, September 30 2001.
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