The factory where I worked had been built in WW1 and was rather 'rustic' in construction. With many roller-shutter doors, it was really not feasible to restrict access for the many lodgers we had.
We had a blackbird in the Development Workshop. He didn't really cause much difficulty for people and was surreptitiously fed by a few. He could recognise everybody and judge their opinion of him. Barry, mentioned elsewhere, was one of the the few who wasn't in favour of him and this caused the bird to respond in kind, deliberately irritating him by gliding down from the crane rails, just behind his line of sight, then swerving to flash by, just in front of his face, causing Barry to display great agitation. I can remember people spotting the bird positioning himself for this, and adjusting their positions, so that the correct flightpath was available.
On another occasion, I saw "one of the bird's friends", with his feet up on the bench, reading a newspaper at dinner-time. His foot was itching and he occasionally moved it to scratch the itch - but, it wasn't itching, it was the blackbird removing his shoelaces for nesting material, merely stepping back as each 'scratching session' occurred.
The bird rarely bothered to go outside, although occasionally strolling through the door onto a grassy area, in hope of a few slugs or worms. This was a reasonable tactic, as we also had a kestrel nesting in a hole through the corrugated wall of the next building...