Crow suffering from OCD (obsessive compulsive disorder)?

A crow has in the last three weeks taken to sitting outside one of my bedroom windows and has pecked all of the rubber/neoprene gasket from the bottom of the window.When I frighten it away it sits in a nearby tree cawing loudly. It returns later and begins where it left off stripping more rubber. The rubber has no food value for the bird. If I partially close the curtains that seems to discourage it from rubber removal although it still perches on the window cill and caws loudly. It appears to be a loner as other crows are not to be seen nearby. The birds persistent and obsessive behaviour intrigues me. I replaced the removed rubber with black silicon sealer, before realising that closing the curtains stopped his little game, and he still pecked at the silicon.I have nick named him Russell as in Russell Crowe. Anybody any ideas as to why the bird has taken such a liking to rubber.