The Brown Skua, also known as the Subantarctic Skua, is a member of the genus Stercorarius in the family Stercorariidae, the taxonomic home of the seven bird species known as Skuas. Skuas are also known as jaegers, a name which comes from the word Jager (German for "hunter"). Stercorarids are in the order Charadriiformes, along with gulls; shorebirds like sandpipers, plovers, and snipe; and other marine avians that share their basic internal physiological characteristics (structure of the skull, vertebral column and syrinx, among other key derived traits). Charadriiformes are neognaths (superorder Neognathae) in Neornithes, the subclass that encompasses modern avian biodiversity and had been evolving since the late Cretaceous period. The fossil record indicates that Charadriiformes and their presumed relatives and ancestors have been roaming the seas and slowly evolving and diversifying for nearly that long, with a particularly notable burst of adaptive radiation at the border between the Oligocene and Eocene epochs, about 35 million years ago (take a look at a paper here from the Geological Museum of the Natural History Museum of Denmark and another from the National Evolutionary Synthesis Center in Durham to further explore Charadriiformes' evolution).
The Brown Skua is the largest member of Stercorarius, reaching 2.13 kg (4.7 lb.) in weight and reaching 65 cm. in length and 160 cm. in wingspan. It is similar in coloration to the Great Skua (Stercorarius skua), a species with which it has at times been grouped with based on their striking morphological similarity – both are a dark grayish-brown in color, with white on the inside of the wings. Young skua are also brown, and covered with downy feathers. Their range spans across the Antarctic Ocean and indeed throughout most Southern Hemisphere waters; they move north, closer to the Equator, in winter. They usually spend time on the coast, nesting on expose headlands near fishing grounds and hunting grounds (more on the Skua's hunting habits later). There are an estimated 10,000 living individual Brown Skuas, with 1,000 breeding pairs in the waters south of New Zealand.
Let me cut to the chase here and list off some reasons why Brown Skuas are particularly incredible (and shockingly monstrous) animals:
- Kleptoparasitism (a fairly self-explanatory term, I must say) is theft of food or prey obtained by another animal. Skuas (along with many other seabirds, including the Great Frigatebird and the Chinstrap Penguin) steal other birds' catches, harassing them until they drop the fish they've collected in their crop.
- In case your opinion of Brown Skuas wasn't already low enough, these birds are ovivores, feeding on the eggs of penguins and other marine birds that happen to nest near to their colonies. They will also eat penguin chicks, striking from above and carrying them off before their parents can notice.
- As brutal as Brown Skuas can be, they're social animals that are remarkably tender with their mates and offspring (as are many seabirds). Courting involves complicated calls and displays, and once the eggs have been laid parents share the duties of defending the nest, incubation, brooding, and feeding the chicks once they hatch.
Like the Great Skua, the Brown Skua is very vulnerable to water pollution, and its populations has also been adversely affected by fisheries by-catch, as well as farmers who view the birds that as a threat to their livestock. Brown Skuas' greatest ecological problems going forward will likely stem from the growing impact climate change is having on the food sources of their prey species.