The BBC reports on some interesting behaviour amongst sparrows, where some will take the side of their neighbours against intruders.
However, the report at least appears to be interpreting this behaviour very differently from the way some Australian scientists interpreted the behaviour of crabs when some would assist their neighbours in expelling intruders. The BBC seems to think this is about not liking the intruders “aggression”. It’s nice to think this is the case, but there are other explanations. The crab researchers figured that crabs knew where they stood with existing neighbours. If the intruder was allowed to usurp a burrow the next door neighbour might need to spend time fighting to defend the boundary between the territories all over again. At the time this was thought to be the first case of members of a non-social species coming to the aid of neighbours against other members of the same species, so it would be interesting to compare how similar the two behaviours are.
When I have more time (ha!) I’ll try to see if the BBC’s angle was their own spin, or based on what the researchers actually said. I’ll also try to post a copy of my article on the crab research.