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

Leach's storm petrel is a small ocean-going seabird that breeds on islands in the North Atlantic and North Pacific. Its dark body, pale rump and bounding flight can make distant identification challenging. Around New England, breeding birds are associated with offshore islands rather than busy mainland beaches. They come ashore mostly at night, so colony presence does not mean visitors will see birds by day or from an ordinary coastal promenade.

Size

18–21 cm long; 43–48 cm wingspan

Weight

40–50 g

Lifespan

Not reliably established

Status

Vulnerable

At sea, these petrels fly with irregular bounds and changes of direction while searching for tiny prey near the surface. Breeding adults occupy burrows or sheltered cavities and usually return after dark, reducing exposure to gulls and other predators. Partners share the long incubation period and feed a single chick. Their calls can be conspicuous at colonies, but entering nesting habitat risks collapsing burrows and disturbing birds that are otherwise hidden. Courtship rituals include aerial chases and vocalizations near nesting burrows. Both parents incubate the single egg, which is laid directly on the soil within the burrow. Chicks remain in the burrow for an extended period, relying on parental feeding of stomach oil before fledging.

• A breeding pair normally lays just one egg.
• Adults usually visit the nesting colony under cover of darkness.
• Its tube-shaped nostrils are characteristic of the seabird order Procellariiformes.
• Some populations once included under this name are now recognized as separate species.

Late spring through early autumn is the most relevant New England window for breeding-season offshore presence. Mainland visibility remains poor even then. Autumn weather can occasionally bring birds closer to shore, but storm conditions are unsafe and should never be sought for sightings. While generally offshore, strong easterly or southerly winds, particularly in late summer and fall, can occasionally push these birds closer to the New England coast. For reliable sightings from a cruise ship, focusing on passages through open ocean far from shore is essential. Early autumn migration can concentrate birds in certain offshore areas, increasing observation opportunities.

They spend most of their lives over open ocean, often beyond nearshore waters. Breeding habitat consists of predator-safe islands with soil, vegetation or crevices suitable for nests. Mainland shoreline sightings are uncommon and often linked to unusual weather. The species is found across both the Atlantic and Pacific Oceans. In New England, nesting sites are restricted to offshore islands and remote coastal areas free from mammalian predators. Their presence often indicates healthy marine ecosystems far from human disturbance.

Small crustaceans, other planktonic animals and small fish are taken close to the ocean surface. Some prey migrates upward at night. Adults convert food into energy-rich stomach oil that can help nourish chicks during intervals between parental visits. They opportunistically consume fish oils or other floating animal matter that may be left behind by fishing vessels, though this is not a primary food source. Their diet can shift seasonally based on the availability of different planktonic organisms. The energy dense stomach oil allows adults to feed chicks less frequently, a key adaptation for offshore foragers.

Common name

Leach's Storm Petrel

Scientific name

Hydrobates leucorhous

Animal group

Birds

Size

18–21 cm long; 43–48 cm wingspan

Weight

40–50 g

Lifespan

Not reliably established

Status

Vulnerable

Identification

Its forked tail, usually divided white rump and bounding flight help distinguish it from Wilson's storm petrel, which has a squarer tail and often patters with projecting feet. Beyond the tail and rump, Leach's storm petrels generally appear darker than Wilson's storm petrels, lacking the prominent pale wing panel sometimes seen on Wilson's. The bill is slender and hooked, and the legs are short. Their flight is often described as bat-like, with deep, quick wingbeats followed by glides.