Wilson’s Storm-Petrels nest in colonies, usually in holes and rocky crevices in Antarctica, subantarctic islands, and off southern Chile, up to elevations of 2,000 feet and sometimes up to 75 miles inland. When not at the nest site, Wilson’s Storm-Petrels spend their lives on the open ocean. Their main food is plankton, which is abundant in cold, nutrient-rich waters, especially where water upwells from the sea floor. Their migrations take them across the equator, into all of the world’s oceans, though they are rare in the North Pacific. Wilson’s pass close to land in some places, but most forage over the deeper waters of the continental slope rather than the shallower continental-shelf waters. Back to top
Like other small storm-petrels, Wilson’s hunts while flying, using both sight and smell to locate food. They hang in the wind over a patch of ocean, scanning for tiny prey (mostly plankton), often holding wings half-open to maintain position, and usually pattering with the feet on the water to maintain stability and perhaps stir up prey. They flutter quickly as they dip the bill to the water’s surface, sometimes putting the head slightly underwater. On occasion, they swim and make shallow dives to reach prey. They prey on tiny crustaceans such as krill (euphausiids) and amphipods, fish (such as lanternfish) and their eggs, squid, marine worms (nereids, polychaetes), and marine snails. They follow whales for the prey that foraging whales bring to the surface, and also for whales’ nutrient-rich feces. They also follow ships at sea, eating fish scraps, small prey items, and bits of garbage and sewage. Wilson’s gather in large numbers at floating carcasses of whales, sea turtles, and fish, picking off pieces of flesh with their bills, usually while in flight. Small flocks probably travel with such carcasses for several days or longer. They also eat oils and other materials left floating on the sea surface after predatory fish have been feeding on smaller prey. Back to top
Nest are set in holes and crevices in cliffs, rock fields, or scree slopes. The adults sometimes dig burrows up to 20 inches long.
Adults sometimes line the nest with feathers, moss, or other soft material.
|Clutch Size:||1 egg|
|Number of Broods:||1 brood|
|Egg Length:||1.3 in (3.3 cm)|
|Egg Width:||0.9 in (2.3 cm)|
|Incubation Period:||41-49 days|
|Nestling Period:||48-78 days|
|Egg Description:||White, often with brownish spots at the larger end.|
|Condition at Hatching:||Covered in dark down and unable to sit up.|
Wilson's Storm-Petrels breed in colonies, often among other seabirds such as prions, and they normally visit their burrows when it is darkest (though in summer at high latitudes, there is no true night). Pairs probably mate for several consecutive years, if not for life, and reunite at their nest site, where they call and preen one another as they prepare to breed. When conditions are dark, Wilson’s often perform aerial displays over the colony, calling loudly and zooming around, sometimes in pairs. In darkness, they can locate their burrows, and even their mates, by smell. After mating, females spend about a week and a half at sea, feeding heavily in order to produce their single egg, in December or January. Both parents incubate the egg and feed the chick, which departs the nest site on its own soon after fledging. At sea, Wilson’s can seem casual, even delicate in their manner of flight, but their wing shape permits them to travel great distances on strong winds. In high winds, they travel much like larger tubenoses, in rollercoaster-like arcs with little to no flapping. Their fairly broad wings and small bodies also permit them to fly and forage in very light winds, unlike some larger storm-petrels. Wilson’s are gregarious at sea, often resting and roosting overnight in large flocks, sometimes in flocks mixed with other species of storm-petrels.Back to top
Wilson's Storm-Petrel population trends are unknown. Partners in Flight estimates the global breeding population at 14 million and rates the species a 9 out of 20 on the Continental Concern Scale, indicating a species of low conservation concern. Heavy metals, pesticides, plastic particles, and other marine pollutants pose a risk to their populations, as do introductions of predators such as rats and cats to their nesting islands. Harvest of krill is also a source of concern. Another major conservation concern is the impact of climate change on habitats and food resources.Back to top
Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.
Sibley, D. (2014). The North American Bird Guide. 2nd Edition. Christopher Helm, London, United Kingdom.