Maybe someone can tell me otherwise but I don't see why birds shouldn't have mental problems, they way some humans do - plenty of dogs do!. The succession of robins in our garden have been tolerant of the birds who come to the feeders. The robin will take seed occasionally, especially if the winter is hard but generally they are insectivorous, I think. Mind you, the blue-tit is supposed to be, too, but they are the kings of our feeders. They don't bully other birds but they just flip away about a foot or so and jump in whenever the perches are vacated. Completely fearless, beautiful birds. Mind you, they're all beautiful, aren't they?!