My mother and her broken rook

Phonecall from my mother to say that she has had a rook with a damaged wing stuck in her back garden for several days, and will I come over and help her catch it so she can take it to the vet as despite being fed and watered and given a perch to sit on, it does not seem to be improving. 

Rooks are Beyond My Expertise, so any tips on rookwrangling would be much appreciated.