Antarctic Prion

Found across the Southern Ocean and breeding on islands stretching from the sub-Antarctic to the Antarctic Peninsula itself, including the South Shetland and South Orkney Islands, the Antarctic Prion is a small, delicate seabird identified by its soft blue-grey upperparts, white underside, and a distinctive dark "M"-shaped marking stretching across its wings and back. It is the largest of the six prion species, though at just 27cm long and weighing around 150g, it remains small compared to most of the seabirds encountered on an Antarctic voyage. Highly gregarious, Antarctic Prions are usually seen in large, fast-moving flocks skimming low over the water, and are so similar in appearance to close relatives like Salvin's Prion that the two are considered indistinguishable at sea, even by experienced observers.

Antarctic Prions feed mainly on krill, along with copepods, amphipods, and other small crustaceans, using a specialised feeding technique called hydroplaning, in which they skim across the surface of the water with feet paddling and bill partially submerged. Their broad, lamellate bill is fringed with comb-like structures that filter tiny prey straight from the water, aided by an expandable throat pouch that helps them process food efficiently. In flight, they are fast, buoyant, and erratic, weaving low over the waves in twisting glides interspersed with quick, shallow wingbeats, and are often seen in flocks numbering in the thousands. A gathering of prions at sea can be a useful sign for spotting whales, since the birds are often drawn to fish pushed toward the surface by feeding pods.

Antarctic Prions arrive at their breeding colonies in October and November, nesting on exposed cliff faces, in cavities under boulders, or in short burrows dug into grass-covered slopes, with experienced pairs often returning to the same site used the previous year. A single egg is laid and incubated by both parents in alternating shifts, with adults visiting the colony under cover of darkness to reduce the risk of predation by skuas. Chicks are fed regurgitated food by both parents until they are ready to fledge, after which they head out to sea, ranging widely across the Southern Ocean until they return to breed themselves in future seasons. The species remains numerous, with a world population estimated in the tens of millions, though like many Southern Ocean seabirds, it faces pressure from habitat disturbance, introduced predators on breeding islands, and changes in krill availability.