LBBG 7cy: Bruxelles L-76225, April 05 2003, Nachtegalenkeet - Maasvlakte, the Netherlands.

An adult with a Bruxelles ring but a bird of uncertain origin, since been caught (as an immature) on a landfill and ringed on that occasion. Ringed as 3cy at Antwerpen, Belgium (51.21N 04.46E) on July 15 1999.
Compared to other LBBG's which were present in the direct surrounding, this adult showed an average tone of grey on the upper-parts in the colony. Ring projects revealed that adults from the UK and Belgium may turn up in Dutch colonies and start mixed couples. 
This large bird is probably a male, still showing black on the upper mandible.
Most feathers are neat grey and the partial spring moult of the upper-parts is almost completed.