Photo 26: LBBG adult Bruxelles L 4483, April 16 2001, Missouriweg Maasvlakte, the Netherlands.

An adult wearing a Bruxelles ring and of uncertain origin, maybe from a Belgian colony but it may also be caught (as an immature) on a landfill and ringed on that occasion.
Compared to other LBBGs which were present in the direct surrounding, this adult showed one of the palest grey upper-parts of the colony. This may refer to another type than the local Dutch intergrades, especially the nominate graellsii, the presumed breeding form in Belgium and the UK. Ring projects revealed that adults from the UK and Belgium may turn up in Dutch colonies and start mixed couples. 
The elegant impression suggests a female.
It seems, most feathers are neat grey and the partial spring moult of the upper-parts is almost completed.