大象传媒

Herring gulls have quite a complex language. Their 'long call' - a very familiar sound at the seaside - is a declaration saying 'I am here and this is mine!', whether it is at the nest or a feeding site. Another call is their main alarm cry, and a third is a low intensity alarm. Why do so many gulls have white plumage? The answer is that they show up at a distance, so when one finds a shoal of fish the others can soon gather there. Why advertise that there's food here at all? It's because the fish are difficult to find. So the gulls spread out over the ocean and whichever finds a shoal can be seen by its neighbours. Everyone benefits from the system.