Birds or other Animals Behaving Strangely

Has anyone else had birds or other animals behaving strangely.  My mum died in 2006.  About a year maybe a bit more before that when she first started to be ill, a large black and white pigeon suddenly appeared and took up residence on their spare bedroom windowsill.  Sometimes it would peck at the window, other times when someone opened the front door it would fly indoors, and Dad would have to shoo it out again.  It always seemed to be on the windowsill, then it would swoop down and peck at callers like the postman.  My Dad asked around if anyone had lost a pigeon - no one had, so a friend took it away.  A day later it was back in residence, so someone else took it away, again it was back within a day.  A neighbour worked in Sussex, (my parents lived in Kent) so he took it with him early one morning and released it at work, but by the end of the day it was back with Mum and Dad again.  Dad reckoned it had a look of Mum's grandmother about it (it looked quite fierce.  Gran was lovely but could look fierce at times) and was her come back to keep an eye on Mum whom she brought up until she was about 7-9.  The strange thing was, as soon as Mum had been taken to hospital the bird vanished into thin air and has never been seen since.  Was Dad right, could it have been Mum's grandmother trying to get Dad moving in getting Mum into hospital.  She'd had Alzheimers for a while and soon after admission was found to have liver cancer as well.  Maybe Gran's job was done after Mum was taken into hospital which is why the bird was never seen again.  Any ideas anybody, please.