Hello. Wondered if anyone could provide me with some insight into robin behaviour. I have four beautiful robins that are regular visitors to the garden, one of which is extremely friendly and all will fly over when called. With my super friendly robin I’ve witnessed him a few times showing strange behaviour to another robin but am unsure if this is an aggressive warning to the other one warning it off or the reverse? He will sing loudly stretching up puffing out his chest but also the feathers on his head stand upright too, what does this mean? ? Thank you in advance xx