Pomarine Skua
Stercorarius pomarinus

The Pomarine Skua (known as a Pomarine Jaeger in the US and other places, after the Dutch name) is a mostly parasitic bird - it harasses other birds into disgorging their food, which it then eats. The skuas are closely related to gulls, which they somewhat resemble.
 

1-3: South Pacific, off Sydney, 13/03/2010.