Peeping from its nest - Arctic Tern, Farne Islands
The Arctic Tern is fiercely defensive of its nest. It will attack humans and predators, usually striking the top or back of the head and is capable of repelling many raptorial birds, polar bears and smaller mammalian predators such as foxes and cats. The nest is usually a depression in the ground, which may be lined with bits of grass. Other nesting birds, often incidentally benefit from the protection provided by nesting in an area defended by Arctic Terns.