Wilson's Storm Petrel: where and when to see them

Wilson's storm petrel is a tiny ocean-going seabird famous for appearing to walk across the sea surface. Dark plumage and a bright white rump make it recognizable when viewing conditions are good, although several related species look similar. It breeds around Antarctica and on subantarctic islands, then disperses widely, with many birds reaching the North Atlantic. New England visitors may encounter migrants from coastal vessels, while Antarctic travelers can see birds during the southern breeding season.

Size

15-19 cm body length

Weight

30-50 g

Lifespan

Not reliably established

Status

Least Concern

Foraging birds hover low over the water, holding their wings raised while their long legs patter against the surface. They pick small prey from the uppermost water layer, often gathering where food is concentrated. Nesting occurs in rocky cavities, generally with visits under low light where seasonal darkness permits. A single egg is laid, and both parents contribute to incubation and feeding before the young bird leaves for an oceanic life. Courtship involves aerial chases and elaborate synchronized flights over the breeding colonies before nesting begins. They are typically colonial breeders, nesting in dense groups to maximize protection from predators. Parent birds engage in nocturnal visits to the nest during the incubation and chick-rearing phases, a strategy to avoid avian predators like skuas.

• Its surface-pattering feeding style inspired the image of a bird walking on water.
• The webs between its toes contain yellow patches.
• Many individuals migrate between Antarctic breeding regions and the North Atlantic.
• A breeding pair normally lays just one egg.

June through September is a useful New England window for northward migrants at sea. November through March corresponds to Antarctic visitor access and the southern breeding period. Neither window makes sightings from land dependable, because birds often remain well offshore. In New England, late summer and early autumn provide the best opportunities as they move north to rich feeding grounds. During the Antarctic summer, sightings are virtually guaranteed when exploring the Southern Ocean by ship. Note that their small size and rapid, erratic flight can make them challenging to spot even in optimal conditions.

Most of its life is spent at sea, from cold Antarctic waters to temperate and tropical oceans. Breeding sites are crevices among rocks and scree on Antarctic and subantarctic land. Coastal visibility depends heavily on weather, food distribution and distance offshore. Though primarily pelagic, they can occasionally be seen from coastal vantage points, especially during stormy weather or strong onshore winds. These highly migratory birds undertake one of the longest migrations of any seabird, traveling between their Southern Ocean breeding grounds and northern hemisphere feeding areas. Breeding colonies are typically found on ice-free ground, often near penguin or seal colonies where guano can enrich the soil and provide nesting material.

Small crustaceans, including krill, are important prey, alongside tiny fish and other marine organisms. Birds collect food at or immediately below the surface. They may investigate natural slicks or feeding aggregations, but observers should not create feeding opportunities with scraps or bait. They employ a unique 'pattering' flight style, tapping their feet on the water's surface to stir up food or maintain position while snatching prey. Wilson's storm petrels also commonly feed in association with cetaceans and pinnipeds, capitalizing on prey driven to the surface by these larger marine predators. Their olfactory sense is well-developed, aiding in the detection of food sources, especially dimethyl sulfide (DMS) released by feeding phytoplankton.

Common name

Wilson's Storm Petrel

Scientific name

Oceanites oceanicus

Animal group

Birds

Size

15-19 cm body length

Weight

30-50 g

Lifespan

Not reliably established

Status

Least Concern

Identification

Long legs projecting beyond a short square tail and yellow foot webs help separate it from Leach's storm petrel, which has a forked tail and more bounding flight. Their overall dark sooty-brown plumage is contrasted by a prominent white rump patch extending onto the flanks, a key field mark. The broad, rounded wings with a pale bar on the upperwing coverts are distinctive during flight. Their flight is characterized by shallow wing beats and a constant, bouncing motion, often compared to a butterfly or bat.