adult: June

Last update of this page: 25-07-05 18:14

At the Maasvlakte colonies in the Netherlands (see map), eggs are hatched by the first week of June and many nests contain three nestlings (breeding season 2001 and 2002). Pulli can be found everywhere. First data in 2001 estimate the colonies to be expanded by over 20%, now approximately 40,000 nests at the Europoort location alone (greater Rotterdam district). New colonies arise at plots which are still not occupied by industrial companies. 

In this picture you see female E832, ringed at the nest at Maasvlakte July 1995, now in her 6th summer and raising three pulli. Normally the elder adults occupy the sites used last year(s), as these birds know safety, feeding routes and places, etc. New colonies seem to be occupied by younger adults, as some ring-data suggest. Older LBBGs disturbed from 'ancient' colonies seem to move less far from the places they were forced to abandon. It's interesting to find out whether new colonies abroad are started by relatively young adults.

Moult:
Raising the pulli is very time consuming and all moult in the wing-coverts is suspended in adults.
In some individuals, head feather moult is started mid-June and only the odd individuals moult coverts at a low pace. 

Counting back from the results of surveys done in August 2001, a small proportion of adult LBBG must have shed inner primaries by June. Last years, we did not collect sufficient material to estimate primary moult scores for this age class in June, so a small survey on 200 adult birds was done. We scored preening and bathing adults from the near colony (several 1.000's breeding pairs). The first estimation was done on arriving birds, checking the age while bathing and check primary moult score again at departure. The table shows the results: 75% of local (!) adult LBBG have still all the primaries old (p1-p10 old) and a small minority of about 20% has started moult with dropping p1.

 

Primary moult score of adult LBBG June 18 2002, at Dintelhaven colony, Maasvlakte, the Netherlands (51.59N,04.02E).
p3 shed	1
p2 shed	11
p1 shed	43
0 shed	145
n = 200. two birds had p2 shed, while p1 was (almost) fully grown, hence followed a "condensed" moult strategy.