Wilson´s Storm Petrel

Is a small, remarkably abundant seabird with a body length of 15 to 19 centimeters and a wingspan ranging from 38 to 42 centimeters. Its plumage is highly distinctive, featuring a dark, soot-colored, brownish-black body that contrasts sharply with a prominent, U-shaped white rump patch that wraps around the sides of the tail. The underwings are dark, while the upperwings display a pale, diagonal bar across the greater coverts. Extremely long, spindly black legs with bright yellow webbed feet are key diagnostic features, with the toes frequently projecting beyond the square tail during flight. The bill is short, black, and equipped with prominent tubular nostrils fused on top, designed for excreting excess salt.

Geographical distribution: Undertakes one of the longest and most spectacular trans-equatorial migrations of any animal, breeding during the austral summer in the Antarctic continent and sub-Antarctic islands like South Georgia, South Shetland, and Kerguelen. Following the breeding season, it migrates northward, crossing the equator to spend the northern hemisphere´s summer in the sub-polar and temperate waters of the North Atlantic, North Pacific, and Indian Oceans. It is frequently observed off the coasts of North America, Western Europe, and East Asia, displaying an almost cosmopolitan pelagic distribution during its non-breeding phase.

Habitat: Leads a strictly pelagic lifestyle, spending the vast majority of its life over open ocean waters, often far from land. It is adapted to navigate diverse environmental conditions, ranging from ice-strewn polar waters to warm tropical zones crossed during migration. The species transitions to a terrestrial habitat exclusively for reproduction, selecting rocky cliffs, talus slopes, boulder fields, and scree in ice-free coastal zones of the Southern Ocean islands.

Feeding: Sustains itself primarily on a diet of zooplankton, with a heavy reliance on Antarctic krill (Euphausia superba), alongside small amphipods, copepods, larval fish, and tiny squid. It is also highly attracted to marine carrion, fish oils, and offal discarded by fishing vessels. Feeding occurs while hovering low over the water´s surface, using a characteristic "pattering" motion where it appears to walk on the water with its yellow-webbed feet while picking food items from the surface film.

Behavior: Exhibits a distinctive, fluttery flight pattern reminiscent of a swallow, combining rapid, shallow wingbeats with short glides close to the water. The unique behavior of pattering on the surface helps stabilize the bird against strong winds while foraging. Highly gregarious at sea, it frequently gathers in massive flocks over upwelling zones or around vessels. On land, the species is strictly nocturnal at its breeding colonies, arriving and departing only under the cover of darkness to minimize the risk of predation by predatory skuas (Stercorarius spp.) and gulls.

Nesting: Commences its nesting cycle during the austral spring and summer, typically between November and December. Rather than building open nests, they locate deep rock crevices, cavities under boulder fields, or excavate small burrows in soft soil to shelter from the harsh Antarctic climate. The female deposits a single white egg, which is incubated by both parents in alternating shifts for 39 to 48 days. Once hatched, the chick is fed a highly concentrated, energy-rich oil regurgitated by the parents. The chick remains in the nest for 54 to 68 days before fledging and departing directly into the open ocean.

Conservation status: Categorized as Least Concern (LC) by the International Union for Conservation of Nature (IUCN). This classification is supported by an immense global population estimated to exceed several tens of millions of individuals and an exceptionally vast geographic range. Despite this stability, potential long-term threats include the impacts of climate change on krill populations in the Southern Ocean, oil pollution, and the introduction of invasive predators like rats and cats on key breeding islands.