Brambling

 
These shy winter visitors, photographed in north London in March 2006, are in their winter plumage and about to start their long flight back
to their breeding grounds in northern Scandinavia and Russia. The heads of some of the males have begun to turn to black breeding plumage.
The north London branch of the RSPB say that this is only the second recorded sighting of bramblings in the Borough of Barnet this winter.
(Apologies for the poor quality of the photos, - light was poor and I couldn't get near enough. Haven't yet moved to digiscoping.)
 

Bramblings are gregarious birds, often to be found "hiding" among flocks of chaffinches