Antarctic or South Polar Skua Displaying
 - Catharacta maccormicki

Displaying skuas. They display to, or for a mate or to other skuas to establish their territory. Sometimes the birds can be seen to do this as a pair, it is quite an impressive sight and the squawking can be heard some considerable distance away. Skuas will also do this if their nest is being approached by an unwanted visitor.  

More often though the first sign that a visitor gets of being near to a skuas nest is of a sudden heart-stopping rush of air through the wing feathers of the parent bird flying at speed past your head from behind, much too close for comfort. If you're particularly unlucky or if its very unhappy at you being so close, then rarely a whack at the back of the head by the front of the wing may result. This is actually quite a good way of finding skua chicks - when the parents start getting upset you know you're very close to the excellently camouflaged chick.

These birds however are semi-tame and are calling to the mate to come quick as there may well be some give-away food. The biggest problem I had taking these pictures shot was getting the birds far enough away as they kept sticking their beaks about 10cm from my lens.