Skuas are a group of predatory seabirds belonging to the genus Stercorarius. They are recognized for their aggressive nature, strong flight, and ability to thrive in harsh marine environments. Skuas exhibit unique adaptations for obtaining food. Related to gulls, waders, and auks, they share some similarities but possess specialized predatory behaviors that set them apart.
Identifying Features and Global Range
Skuas are medium to large birds, displaying plumage in shades of brown or gray, sometimes accented with white markings on their wings. Their size ranges from the Long-tailed Skua (around 310 grams) to the Brown Skua (up to 1.63 kilograms). An average skua measures about 56 centimeters in length with a wingspan of approximately 121 centimeters. They possess robust bodies, long bills with a hooked tip, and webbed feet equipped with sharp claws. Some species, like the Arctic and Pomarine Skuas, can exhibit different color phases, ranging from light to dark morphs.
These seabirds are globally distributed, inhabiting polar and subpolar regions for breeding. Their breeding grounds are primarily in the Arctic and Antarctic, where they nest on the ground in open areas. Skuas are long-distance migrants, traveling between their breeding and wintering areas. For instance, Great Skuas travel from North Atlantic breeding grounds to South Atlantic wintering areas, covering thousands of miles annually. Arctic Skuas breed along the coastlines of Eurasia and North America before migrating to the southern tip of South America, parts of Africa, and even Australia and New Zealand for winter.
Distinctive Feeding Habits and Behavior
Skuas are known for their predatory nature and unique feeding strategies, with a diet that includes fish, small mammals, eggs, and the chicks of other birds. They are also opportunistic scavengers, consuming carrion, offal, and sometimes even kitchen waste. A primary aspect of their behavior is kleptoparasitism, where they harass other seabirds to steal their caught food. They pursue birds like gannets, gulls, terns, and puffins, forcing them to drop or regurgitate their meals, which the skuas then seize. This “piratical” behavior is a primary feeding method for many skua species, especially outside the breeding season.
Beyond stealing food, skuas actively prey on smaller birds and their young. Great Skuas, for example, hunt small birds, rodents, and rabbits, and are known to take eggs and chicks from other seabird nests. During the breeding season, some skua species, particularly those in the Arctic, may rely on terrestrial prey such as lemmings. Skuas are territorial and aggressively defend their nests from intruders, including humans, often dive-bombing them.
Species Diversity and Conservation
The skua family (Stercorariidae) comprises seven species, with some referred to as “jaegers” in North America. Notable species include the Great Skua, Arctic Skua (also known as Parasitic Jaeger), Long-tailed Skua (Long-tailed Jaeger), and Pomarine Skua (Pomarine Jaeger). For instance, the Long-tailed Skua is generally smaller and more slender than the Arctic Skua, while the Pomarine Skua is larger and more robust.
While some skua populations are “Least Concern” globally by the IUCN Red List, many face regional declines. The Arctic Skua population in the UK, for example, has seen significant declines, with a 70% reduction between 2000 and 2019 in Scotland. Threats to skua populations include climate change, impacting food availability and migration patterns. Other challenges stem from pollution, such as plastic waste, and habitat destruction. Avian influenza outbreaks have also led to mortalities in skua populations, including the Great Skua. Conservation efforts focus on understanding their migration patterns and mitigating these environmental pressures.