A lot of cultures in every part of the world have superstitions, myths, fables, stories, symbols, beliefs, omens etc that relate to birds in some way, so many people would have been told these things from childhood and may or may not believe them. I think there is a lot in this world that has no rational or scientifically provable explanation. For a lot of circumstances it is how we personally choose to interpret things within our own belief system or realm of experience. Personally I am OK with birds being in the house and will always try to get them back outside, unharmed, one way or another (encouraging them to leave or sometimes catching and quickly releasing them - including a few the cat has come home with!)
It's interesting how this post has created so many responses relating to various omens and the supernatural world. Discussions on how we 'sense' or 'feel' things, seem to know things when logic says the opposite, sometimes predict deaths or other big events in life, have some sort of contact with, or sense of, an afterlife - all fascinating. I've had a few uncanny experiences in life but as they are not directly related to the original post I'll save them for another time and another thread.
Also great that Gransnet encompasses such a wide range of beliefs & opinions where people can 'agree to disagree', debate respectfully and avoid a lot of the judgemental attitudes present in a lot of online forums or social media platforms.