Rookery

 Rooks are collecting nest material and squabbling  in the treetops as they build and repair their nests making it difficult to avoid the falling twigs when below.
They are gregarious birds and congregate noisily in large rookeries built in tall trees.
Rooks can be distinguished from carrion crows by the bald patch below the beak and the baggy trouser appearance of the plumage around their legs.