Why mob if it’s so dangerous? It’s a good way to expose a predator and to drive it off, especially when young are at risk. It’s also a way to impress on inexperienced birds a predator’s dangerous nature, offering so-called teacher benefits. A naïve bird watching other birds mob a threat teaches that bird to fear it, too, and to either avoid it or mob it more strongly, creating more knowledgeable informants and mobbers. There’s strength in numbers.
