I had a seagull stuck in my garden once and refusing to fly away, after two days of it swarking and shitting everywhere whilst getting weaker and weaker and less able to scare the local cats off I called the RSPCA.
They told me that they wouldn't come to get it unless it was in 'imminent danger'.
When I (tongue in cheek) suggested that if it didnt fly off soon I was going to hit it with a brick and was that imminent enough for them they went crackers and told me I'd be prosecuted.
They also didnt react well to me pointing out that without them coming out and helping it then perhaps me offing it quickly was the kindest thing to do.
Eventually a friend managed to get a local bird sanctuary to take it.