Rarely seen inland, Leach’s petrels breed on the remotest offshore islands in the northern hemisphere from Alaska across Canada and Russia as far east as Japan. Once the breeding season ends, southward migration to the Atlantic and Pacific oceans occurs, with sightings rare as they spend winters far out at sea.
Leach's Storm Petrel
Family:Petrels and shearwaters
19cm to 22cm
45cm to 48cm
40g to 50g
Male and female leach’s petrels are alike in appearance and size. They have angled wings, a short forked tail and tubelike nostrils at the top of their black hooked bill.
Leach’s petrels are a dusky black-brown, with a white rump patch visible in flight. Their upperparts have a grayish wash, and their wingtips and tail are darker. A pale wingbar runs diagonally from the bend in the wings.
Although Leach’s petrels do not molt into an alternative plumage post-breeding, their feathers develop a browner, worn appearance.
Juvenile Leach’s petrels have the same plumage as adults and are initially very heavy and rounded, but slim down ahead of their first winter migration and are only distinguished from adult birds as their coloring is richer and less worn.
Leach's Petrel in-flight
Leach’s petrels are relatively small seabirds, larger than the European petrel and Wilson’s storm-petrel. Male and female Leach’s petrels are the same size and weight, making it impossible to tell them apart on sight.
Chattering calls can be heard on the ground at breeding colonies as well as in flight overhead. Purring sounds are made within breeding burrows both while incubating and post-hatching. A harsh shrieking cry signals alarm or distress at the presence of a threat or predator.
The main prey of Leach’s petrels includes fish, crustaceans, squid, octopus and jellyfish. Chief fish species eaten are rockfish, sand lance and cod.
Leach’s petrels initially regurgitate an oily substance produced in their own stomachs into the bills of their young. After a few days, partially digested shrimp and squid, coated in the same musky stomach oils, are also added to their diet.
Leach’s petrels breed on islands that are as free as possible from land predators, with remote offshore islands with adequate soil for borrowing a popular choice. Sometimes rocky crevices are used if the landscape is lacking soil.
They feed out at sea in deep water over the continental shelf, undertaking mammoth journeys of up to 800 km (500 mi) to foraging grounds before returning to their colonies.
Winters are spent at sea, and once breeding is complete, Leach’s petrels do not come inland unless blown off-course by strong and stormy weather.
Leach’s petrels breed on remote, offshore islands across the entire northern hemisphere, including Atlantic islands in the Atlantic Ocean from Norway westwards to Massachusetts and on islands in the Pacific Ocean from Baja California east to Hokkaido, Japan. No breeding occurs in Greenland.
Once breeding is finished, Leach’s petrels leave their breeding grounds and disperse southwards to spend winter months at sea, as far south as the tropical oceans.
Among the largest breeding settlements of Leach’s petrels are the Newfoundland islands of Baccalieu Island, with 1.95 million pairs, Great Island, with 134,139 pairs and Gull Island, with 179,743 pairs, in eastern Canada.
Colonies on Daikoku Island in Japan are home to 276,000 breeding pairs, and up to a further million pairs breed at Buldir Island in Alaska’s Aleutian Islands.
The wide winter dispersal of Leach’s petrels makes it particularly difficult to estimate populations in different parts of the world. Between 300,000 and 2 million birds spend winter in the Bay of Biscay between France and Spain.
The global population of Leach’s petrels was estimated at 20 million in 2004, and more recently estimated at between 6.7 and 8.3 million breeding pairs. So while they are a numerous species and have a large distribution range, particularly during the non-breeding season, sightings are rare due to their preferred surroundings of ocean waters far from land and their nocturnal habits on breeding grounds.
On a handful of UK islands, Leach’s petrels are not uncommon, with around 48,000 breeding pairs on islands off the northern and western coasts of Scotland.
Leach's Petrel in-flight over the sea
Leach’s petrels breed in Alaska’s islands, as well as off the Pacific Coast from Washington to California. Alaska’s Buldir and Chagaluk islands have 900,000 and 250,000 breeding pairs respectively, and Oregon’s offshore islands welcome around 241,000 pairs annually.
On the east coast, some smaller-scale breeding also takes place on the Atlantic islands offshore of Massachusetts and Maine. As they are nocturnal birds when breeding, sightings are not common.
Newfoundland is home to the world’s largest breeding colony of Leach’s petrels: Baccalieu Island welcomes up to 1.95 million pairs, estimated to be around 25 percent of the global population.
The best time of year for spotting a Leach's petrel is autumn, as birds are migrating towards tropical seas. Strong winds frequently blow petrels closer to shore, so look for them after stormy weather, particularly along the south coast of England and the north coast of Wales. Breeding in the UK is limited to five sites in the Western Isles, including the St Kilda archipelago and the Flannan Isles and two islands in Shetland.
Leach’s petrels have an average life expectancy of around 13 years, although the oldest recorded individual reached 29 years and 5 months. They breed for the first time from 5 years old, although pairs may form a couple of years before the first breeding attempt.
During the breeding season, land mammals are a serious threat to Leach’s petrels. Nest burrows are frequently dug up by rats, dogs, cats, pigs, and Arctic and red foxes. Several owl species, including little owls, barn owls, long-eared owls and great-horned owls, are known avian predators on breeding grounds.
At sea, sharks can pose a major threat to Leach’s petrels in tropical waters.
Leach’s petrels are protected by the Canadian Migratory Birds Convention Act of 1994 and the Migratory Bird Treaty Act of 1918 in the United States. In the UK, similar protection is given to the species as Schedule I birds on the Wildlife and Countryside Act, 1981, making it an offense to destroy or damage their nests, young, or eggs, and kill, injure, or capture an adult bird.
Leach’s petrels are rated as a Vulnerable species on the IUCN list, and classified as Near-Threatened under the Species of European Conservation Concern framework. In the UK, Leach’s petrels have Red status on the British Birds of Conservation Concern list. Numbers are hard to estimate due to the wide range and offshore wintering grounds, but estimates suggest significant declines since the 1990s.
Males build nest burrows into the earth at breeding colonies, always at night and under cover of darkness. Soil is scooped out using the bill and feet, and a burrow of around 45 cm (18 in) long and 13 cm (5 in) deep is created. Some lining material may be added, such as moss, grass, or twigs. Burrows may be reused by returning pairs the following year.
The peak laying time for Leach petrels falls in late May to mid-June, although the further north, the later in the year nesting begins. Incubation is shared between both mates, with males taking longer shifts, lasting around 3 days at a time. Hatching begins after between 32 and 50 days.
A single egg is laid each season, measuring 33 mm by 24 mm (1.2 in by 0.9 in). Eggs are creamy white in color and speckled with reddish-purple flecks.
It’s common for leach petrel pairs to reunite and breed together at the same nest site for several successive years. If a previous breeding attempt has been successful, it is likely that the pair bond will be strong and they will breed together again the following year. The longest-recorded pair bond survived for 22 years.
Leach’s petrels are communal nesters, raising their young in colonies that range from a couple of pairs to up to 2 million pairs. No territorial behavior is displayed and leach’s petrels are regularly observed foraging in flocks.
During winter, Leach’s petrels are thought to roost on the waves out at sea. During the breeding season, adults sleep in burrows on land while incubating eggs or brooding young.
Leach’s petrels leave their breeding grounds once their young are independent and head to tropical ocean waters where they spend the winter months out at sea.
Leach’s petrels only come inland during the breeding season and survive on a diet of marine fish during winter months. They have no need to be ashore once breeding has finished and the tropical oceans support all their feeding requirements until they return north the following spring.
The European storm petrel is a small seabird that spends much of its life feeding on fish over open waters, only coming into land to roost overnight and to breed. The species is traditionally associated with rough, stormy seas, hence the name ‘storm petrel’.
Known for their epic circular annual migrations, sooty shearwaters breed in the Southern Hemisphere, before undertaking a lengthy clockwise tour of Northern Hemisphere ocean waters before returning to their original southern nesting colonies and repeating the process.
The Manx Shearwater is a widespread migratory seabird of the Atlantic Ocean. Famous for their impressive lifespan and homing abilities, some individuals will travel a million kilometers or more in their lifetime.
Unlike many migratory bird species, the great shearwater breeds in the southern hemisphere and spends the non-breeding season in the northern hemisphere, wandering across the Atlantic Ocean. Nesting sites are limited to a handful of locations in the South Atlantic, and apart from breeding, the species almost never comes ashore.
Although gull-like in size, fulmars (Fulmarus glacialis) are related to the albatross and spend extended periods of time at sea, gliding over the Arctic waters where they feed in large flocks. They only come inland to breed, establishing extensive colonies on rocky clifftop ledges.
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