ORDER
Procellariiform.es
FAMILY
Procellariidae
GENUS & SPECIES
KEY FEATURES
• Spends eight months a year out at sea, following currents and winds for fish and squid
• Glides effortlessly, skimming the ocean waves and only rarely flapping its long, slender wings
• Nests on remote islands, but travels to and from its burrow by night as it’s defenseless on land
WHERE IN THE WORLD!
Breeds on offshore islands in the northeastern Atlantic (Iceland south to Madeira), along the east coast of North America and in the Mediterranean; wanders the South Atlantic from August until April
Lifecycle
A master of navigation and energy-saving flight, the Manx shearwater spends much of its life flying over the open Atlantic, coming to land for only a few months each year.
Habitat
A Nest holes Colonies look deserted by day: all birds are at sea or incubating underground.
One of the Atlantic Ocean’s great wanderers, the Manx shearwater only comes ashore to breed, nesting on offshore islands in huge colonies. It arrives at its Northern Hemisphere breeding grounds in April: the timing depending on the latitude of each colony.
In the breeding season (just over four months), the shearwater stays within a couple hundred miles of its colony. In August, it begins a marathon journey to the South Atlantic, where it spends the Southern Hemisphere’s summer in the warm seas between Brazil, Uruguay and Argentina in the west and South Africa in the east.
The Manx shearwater is named after the Isle of Man, in the Irish Sea, but it no longer breeds there.
The wailing of breeding Manx shearwaters was once thought to be evil spirits.
By the time it fledges, a well-fed juvenile can weigh twice as much as its parents.
A leg-banded juvenile was found in Brazil 17 days after it left its burrow in Britain — over 4,350 miles away.
Behavior
The shearwater is a highly social bird and is rarely seen on its own. It flies in tightly packed flocks, which dart over the sea like squadrons of low-flying aircraft, twisting and turning in sequence to take advantage of the air rising up between waves. As it rarely has to flap its wings, flying is effortless and uses little energy.
The shearwater’s amazing “homing” ability, which isn’t fully understood, but may involve an internal “map” of the sun and stars, lets the bird find its way across expanses of open ocean, with unerring accuracy.
A Nocturnal crooner silent most of the year, the shearwater cackles and “moans” at its colonies.
Breeding
A Finding its way A shearwater finds its burrow, remembering certain “landmarks.”
Change of owner The shearwater may nest in an old rabbit burrow; the Atlantic puffin may use it next.
Conservation
The Manx shearwater faces few threats at sea. It isn’t dependent on a single type of prey and is less vulnerable to oil slicks than seabirds that spend most of their time on the water’s surface. But the story is mixed at its colonies. On some islands, introduced predators (foxes, cats and rats) reduced local populations. However, where islands have been made into nature reserves, the bird thrives.
In the early spring, shearwaters congregate off coastal islands to prepare for their annual return to dry land.This takes place under the cover of darkness, as their awkwardness on land makes them vulnerable. Birds that have bred in previous years search out their old nest burrows and renovate them, but young adults must find an abandoned burrow or dig one. With thousands of shearwaters breeding close together the competition for burrows is intense.
The female lays one large egg, which both parents incubate in shifts for 7-8 weeks: while one bird is sitting on the egg, the other feeds at sea, often wandering hundreds of miles away Once
the chick hatches, the male and female leave it unattended during the day while they hunt, each feeding it at night. It quickly becomes fat, but by the end of August, its parents stop feeding it and leave the colony. Driven by hunger, the chick makes the hazardous journey down to the sea and sets off on its long journey south for the winter.
Food & feeding
A Sunset strip As the sun sinks, the birds fly from their feeding grounds at sea (above) to their colony (below), to feed their chicks.
The shearwater hunts fish, small squid and crustaceans that live close to the sea’s surface. It catches its prey in two different ways: by snatching it from the surface while paddling or by plunging underwater to give chase. Its dives are fairly shallow and last just a few seconds, but the shearwater has been found trapped in lobster traps in over 100′ of water; proving that it dives deeply if necessary
Where food is plentiful, hundreds or thousands of shearwaters gather on the sea in scattered groups known as rafts; squabbles may break out, but the birds usually feed together in peace. When parents have a chick to feed, they make the nightly flight back to their burrow with food; at other times, they stay at their feeding grounds. Unlike other seabirds, such as gulls and gannets, the Manx shearwater doesn’t follow ships to pick up scraps thrown overboard.
at the end of the day…
Feeding party…
By day a raft of shearwaters may float on the surface, plundering a large shoal of surface-feeding fish.
Homeward bound…
As dusk falls, flocks of birds begin to leave, “pattering” along the sea to gather speed to take off.
Crash landing…
Back at the colony, each shearwater finds its own burrow, flopping down on legs poorly adapted for walking.
Messy business
A parent crawls into the nest to regurgitate a mix of oil and partly digested fish for its chick.
PROFILE
Manx Shearwater
Gliding on its long, straight wings, the Manx shearwater is completely at home above the vast open ocean, where it can smell prey from afar.
Creature comparisons
It’s difficult to tell shearwaters apart, since they fly fast and low over the ocean, disappearing into wave troughs and only come to land after sunset The Manx and little shearwaters (Puffinus assimilis) are no exception.
But the little shearwater is one of the smallest true shearwaters, with a wingspan of just 2′. Although both have dark, blackish upperparts that contrast with pale undersides, the little shearwater has more white on its face, giving it a different facial “expression.” It’s widespread, breeding in the North Atlantic and the oceans between South Africa and Australasia.
VITAL | ||
STATISTICS | ||
Weight | 12-16 oz. | |
Length | 1′ | |
Wingspan | 3′ | |
Sexual | 5 years | |
Maturity |
Breeding Season | April-August |
Number of Eggs | 1 |
Incubation Period | 51-54 days |
Fledging Period | 70 days |
Breeding Interval | 1 year |
Typical Diet | Fish, small squid and crustaceans |
Lifespan | Up to 20 years |
RELATED SPECIES
• Nearly a third of all seabirds belong to the order Procellariiformes, including the 20 species of shearwaters, and prions, albatrosses, fulmars and petrels. The tiny Wilson’s storm petrel, Oceanites oceanicus (below), is the most common of all seabirds.