A buzzard seen nearby has been continuously attacking people for over a year now. As far as I know this isn't normal behaviour, especially not outside breeding season. Please correct me if I'm wrong. While not 100% sure this is the same animal it surely looks like it because it is always in the same place (let's say plus/minus 100m), the style of attacks is always the same (from behind, usually just flying over a person's head but sometimes effectively scratching them, sometimes severely), and simply because according to biologists I talked to such attacks are fairly rare and it would be exceptional if a whole bunch of them behaved like that.
Another story: years ago we had a male common blackbird in the garden which without any obvious reason started to produce it's alarm sound from sunrise to sunset, almost non-stop, without any evidence whatsoever of any danger (no predators to be seen, no humans, not a single of the many other birds of all kinds of species sounding alarmed). This lasted for about 2 weeks then it stopped for unknown reasons - one possibility being the bird died. In any case, this again isn't exactly standard behaviour. I've been around blackbirds my entire life but never have witnessed something like that.
So just like people can develop mental problems, both cases always led me to think those birds had mental problems. Would that be a feasible explanation? Or is that not regarded as a proper diagnostic for bird whereas it is for humans? Are there other known cases, possibly studies? Could the cause of such behaviour be genetic, a virus, bactaria, parasite perhaps? Or just some disfunction with hard to track cause (again, like for some humans)?