Apart from the misconception that Carrion Crows tend to be somewhat solitary birds - or at least not colonial - whereas Rooks, being colonial birds tend to be seen in groups, those groups of the crow family that can be seen sometimes numbering over a hundred individuals on Wanstead Flats are almost invariably Carrion Crows, often with (nowadays) numbers of Jackdaws. Rooks are very occasional visitors to our area, as was the case with this one. In fact, this one was the first that I had ever seen. It was a young one, and associated with the Carrion Crows, to my knowledge, for a week or so.