The south polar skua is a medium-sized predatory bird living in Antarctica. One of the features that stands out about these birds is their small head relative to their body size. They also have thinner and more hooked beak than most other skuas do. Another difference is that they have and narrower wings than other birds in the same genus. In color, the south polar skua is various shades of brown, gray, and tan with maybe a little bit of white. Females usually have paler plumage than the males do. Although not all of them have much gray, they have more of this color than most other skua species do.
There are two different color morphs of the south polar skua. A morph is a certain set of a species that is slightly different from the other morphs. Usually the difference is in the color. Morphs do not depend on anything other than genetics. The two morphs of this bird are the light morph and the dark morph. The light morphs are mostly gray while the dark morphs are mostly brown, Their bills and eyes are not much different than the color of their feathers. The individual shown above is probably in neither of these morphs, but is somewhere in between.
Adult south polar skuas are usually between 20 and 22 inches (50-55 cm) in length with a much larger wingspan of between 51 and 55 inches (130-140 cm). The females are usually larger than the males. These birds have a rather large weight range as adults. They can be anywhere from 2 to 3.5 pounds (900 to 1,600 g). Again, females weigh more than the males do.
Diet and hunting
The main foods of south polar skuas are fish, particularly the Antarctic silverfish, and krill. They will usually catch these foods by diving into the ocean and grabbing them with their beaks, but they will sometimes just sit on the ocean surface before diving down. They will also sometimes steal fish from other predatory birds. Sometimes they do this by grabbing the other bird with their beak and forcing it to regurgitate its last meal. Fish and krill are not the only foods for the south polar skua. In the nesting season they will also eat eggs and chicks of other birds or even the carrion from other birds. In areas where the larger brown skuas also live, it is harder to compete for food like this. Here they usually eat just aquatic food.
Habitat and range
South polar skuas are considered to be the southernmost breeding of all birds. There have even been some breeding individuals seen at the Amundsen Scott Station at the South Pole! These birds migrate a lot, and after the breeding season they fly as far north as Alaska and Greenland! Their breeding season is spent only in Antarctica, but during summer in the Northern Hemisphere, which is winter in the Southern Hemisphere, the south polar skuas will migrate to many different places such as California, New England, New Zealand, Japan, Canada, and Alaska and Greenland as mentioned above.
As you can probably tell by their diet, these birds usually live near the sea, at least when they are not breeding. Their breeding areas are also normally near the coast. If there is no good breeding ground left near the coast, or the pair decides not to breed near the coast, they will travel inland and nest in a place where there is not much precipitation.
Status and threats
The IUCN Redlist classifies the south polar skua as Least Concern. Despite this, there are not actually a whole lot of these birds in the wild. There are an estimated 10,000 to 20,000 individuals with only about two thirds of them being fully mature birds. Part of the reason there are not a large amount of south polar skuas is that they have a low breeding success rate. The harsh weather of Antarctica and the threats of other predatory birds makes it more likely for one of the babies to die than to survive. Oil spills and other forms of pollution are threats to birds of all ages. While hunting, the adults are sometimes accidentally caught in fishing nets. Over-fishing can also be a threat as this causes the south polar skua’s food to become harder to find.
The breeding season of these birds begins in October when summer is starting in Antarctica. The south polar skua is extremely territorial and will protect its nesting area vigorously. Pairs usually stay together for life, and most of the time they keep their nest in the same place each year. The best places for nests are sheltered locations without snow or ice as these can freeze the eggs. The female lays two pale green eggs between late November and late December. Three to five weeks later they hatch. Just one or two days after this, the chicks leave the nest to walk around, but they do not fly for thirty to forty more days. Most chicks do not survive. The main reason for this is that the older of the two chicks will sometimes push the younger one out of the nest, leaving it highly vulnerable to starvation or predation. These birds usually breed for the first time between 7 and 9 years of age. In the wild they can live 25 years or more.