Damage to mature trees by rooks?

[Phil Smith]

Hi,

Does anyone know of instances where rooks have been proven to damage the crowns of 
mature trees (cedars)? I am partly responsible for managing an 18 acre wood 
near Crediton, Devon which supports a thriving rookery. Although I'm not in favour 
of the rooks being culled, some other residents claim that it is the rooks that have 
caused the crowns to die back. I think it may be the other way round - that the 
rooks have moved into the trees as they became more suitable due to natural die-off 
(they are rather old cedars). 

Unfortunately the other residents have been here longer and claim they know better. 
Any ideas?

Phil Smith