The bird that can dive up to 35 m is around us

hoagolhaaIt was in the 80s. “Mom, there is a bird screaming and cackling. It’s eerie,” in the dim light of kerosene lamps, I remember asking my mom about a bird that screamed almost every night. My mom clarified by saying that it was Hoagolhaa. The high pitched calls of the bird were heard from a coconut palm tree in a nearby household. According to people, it was a strange bird of the night. Some people said hoagolha was a large bird that came from the sea. These are the information that we know at that time.

The bird’s twittering calls and mewing are often only heard at night. When I searched for information about this bird, a piercing cry usually is given when they rest in groups on the water. The calls of flesh-footed shearwaters resemble cats fighting, with loud wailing and moaning. I always love birds and nature.

One of my favorite birds is the yellow bittern or raabol (raabondhi) and the eagle or locally called baanzu. I remember my father keeping a tame yellow bittern in my house for more than two years, in the 80s. The tame bird stayed on a wooden slab, fixed at about 6ft from the ground. It stayed in the slab and would fly away three or four times a day to kilhi- fresh water lake- for hunting fish. Then  it  returned to the slab. I have not seen a hoagolha while I was living in my island (till 1987). According to people the bird is unusual and “not good-looking.” And its weird and uncanny. Therefore superstitious fear obsessed us.

But most of the stories or information about this bird is not ture. All are myths. I tried to gather information about this bird and was able to get fascinating information. Read the information about the plunging and diving skills of these birds at the bottom of this article. I have listed and extracted information of the four types of  these birds found in the Maldives. I have categorized.

These birds are called shearwaters. They are medium-sized long-winged seabirds. There are more than 30 species of shearwaters. In our country four main types of these birds are found. They are Hoagulha– Streaked Shearwater, Dhivehi Hoagulha– Audubon’s, Shearwater, Bodu Hoagulhaa– Wedged-tailed Shearwater, Maa Hoagulhaa– Flash-footed Shearwater.

Hoagolhaa is called Audubon’s Shearwater (Puffinus lherminieri). The great shearwater feeds on fish and squid, which it catches from the surface or by plunge-diving. It readily follows fishing boats, where it indulges in noisy squabbles. This is a gregarious species, which can be seen in large numbers from ships or appropriate headlands. This seabird is widespread in the Atlantic, Pacific, and Indian oceans, mostly in tropical waters; in North America, it is regular over warm waters off the southeastern coast. At sea it is usually solitary or in small groups.

Hoagulha – Streaked Shearwater

The streaked shearwater is a large, pale-faced shearwater that breeds in Asia and migrates to the waters between Papua New Guinea and Australia. Although they are regularly seen off the east coast of Australia, no live birds have been seen in New Zealand, where the sole record is a beach-wrecked bird found on Kawhia Beach in February 2006.

Identification

The streaked shearwater is a large, long-tailed shearwater, mottled pale brown above with a white face and underparts. The underwings are mainly white, with dark flight feathers and some dusky marking on the outerwing and behind the leading edge. The bill is long and slender, pale grey-horn with a dark tip. No other large shearwater is pale above the eye.

Similar species: Cory’s shearwater, a vagrant to New Zealand from the Atlantic [1 record], has a yellow bill, more uniformly coloured upperparts, dark head and whiter under-wings. Pink-footed shearwater, a vagrant from South America, has a dark head, and a pinkish bill with a dark tip.

Distribution and habitat

Streaked shearwaters breed on islands off the southern Russian Far East, and Japan, east China, Korea and Taiwan. In the non-breeding season they migrate to waters off New Guinea and northern Australia and the South China Sea.

Population

The global population of streaked shearwaters is estimated to be about 3,000,000 birds.

Threats and conservation   

The streaked shearwater population is thought to be declining gradually. Introduced rats are known to be affecting some colonies in Japan and South Korea. Fisheries by-catch may be a problem and some chicks are still taken for food, although adults are considered to be unpalatable.

Breeding

The streaked shearwater is a colonial breeder that lays a single egg in a burrow. Colonies are usually in a well forested area, where tree regeneration may be adversely impacted by the birds.

Behaviour and ecology

In tropical, non-breeding areas streaked shearwaters are more active during the day than at night.  They feed principally on prey driven to the surface by subsurface predators such as tuna.

Food

Streaked shearwaters usually only dive to about 3 m depth. They feed mainly on fish and squid.

Dhivehi Hoagulha – Audubon’s Shearwater

A majestic seabird with large, elongated wings and a streamlined body, Audubon’s shearwater (Puffinus lherminieri) is superbly adapted for gliding on thermals far out at sea. This graceful seabird has a long, thin, serrated bill with a small hook that enables it to catch and hold onto its slippery fish prey. Much less suited to life on land, Audubon’s shearwater has legs that are set far back on its body and provide very little support, so it moves on the ground by shuffling rather clumsily along on its breast. Audubon’s shearwater has a typical shearwater.

Biology

While usually solitary outside of the breeding season, Audubon’s shearwater gathers into large feeding groups in areas where its fish, squid and crustacean prey is in abundance. By circling overhead, it targets its prey and then dives headlong into the water, using momentum to combat its buoyancy, and catches its prey in its long, serrated bill. As with other members of the family Procellariidae, or tubenoses, Audubon’s shearwater has a nasal salt gland, which enables it to excrete excess salt obtained from drinking salt water.

A colonial nesting bird, Audubon’s shearwater lays a single egg every 10 to 12 months in a cavity or burrow, to protect the young against aerial predators. During the breeding season, the male and female birds usually only emerge from the nest at night, when the risk of predation is lower. However, one population of Audubon’s shearwater on the Galapagos Islands has adapted to daytime activity while breeding to avoid predation by owls. The male and female birds take turns in incubating the egg, which hatches after approximately 51 days. Both adult birds collect food for the chick . Audubon’s shearwater reaches sexual maturity at eight years of age and usually mates for life, returning to the same nesting spot year after year.

Audubon’s shearwater description

A majestic seabird with large, elongated wings and a streamlined body, Audubon’s shearwater (Puffinus lherminieri) is superbly adapted for gliding onthermals far out at sea. This graceful seabird has a long, thin, serrated bill with a small hook that enables it to catch and hold onto its slippery fish prey. Much less suited to life on land, Audubon’s shearwater has legs that are set far back on its body and provide very little support, so it moves on the ground by shuffling rather clumsily along on its breast.

Audubon’s shearwater has a typical shearwater colouration of dark brown upperparts and white on the sides of the face and the front of the neck. The belly and brown-edged under-wings are also white, with this being most conspicuous when the bird is in flight. The Audubon’s shearwater chick is a grey, downy ball of feathers.

Shearwaters are named for the way in which the wings, held stiff and motionless, shear the water’s surface as it glides fast and low over the waves.

Biology

While usually solitary outside of the breeding season, Audubon’s shearwater gathers into large feeding groups in areas where its fish, squid and crustacean prey is in abundance. By circling overhead, it targets its prey and then dives headlong into the water, using momentum to combat its buoyancy, and catches its prey in its long, serrated bill. As with other members of the family Procellariidae, or tubenoses, Audubon’s shearwater has a nasal salt gland, which enables it to excrete excess salt obtained from drinking salt water.

A colonial nesting bird, Audubon’s shearwater lays a single egg every 10 to 12 months in a cavity or burrow, to protect the young against aerial predators. During the breeding season, the male and female birds usually only emerge from the nest at night, when the risk of predation is lower. However, one population of Audubon’s shearwater on the Galapagos Islands has adapted to daytime activity while breeding to avoid predation by owls. The male and female birds take turns in incubating the egg, which hatches after approximately 51 days. Both adult birds collect food for the chick. Audubon’s shearwater reaches sexual maturity at eight years of age and usually mates for life, returning to the same nesting spot year after year.

Audubon’s shearwater range

Audubon’s shearwater ranges across tropical parts of the Indian Ocean, as far north as the Arabian Sea, throughout the north-eastern and central Pacific Ocean, and the western Atlantic Ocean, including the Caribbean Sea and Gulf of Mexico. It nests on islands, including off the United Arab Emirates shoreline, the Seychelles, the Galapagos, some of the Caribbean islands, and the Bahamas .

Habitat

Audubon’s shearwater breeds mainly on oceanic islands, coral atolls and rocky offshore islets, where it builds its nest on cliffs and earthen slopes. It spends the majority of its life gliding above marine environments, including both coastal and deep waters.

Bodu Hoagulha

The wedge-tailed shearwater is the largest tropical shearwater, and occurs in two plumage forms: dark-bellied and pale-bellied. They are widely distributed throughout the tropical Pacific and Indian oceans, where they breed on tropical or subtropical islands, including the Kermadec Islands. Wedge-tailed shearwaters rarely reach waters off the New Zealand mainland, with most seen at sea off the north-east coast, and a few beach-wrecked on North Island coasts. Pale-bellied birds are rare in the South Pacific and western Indian Oceans, but comprise 20-30% of the Western Australian population, and almost 100% of the Hawaiian population.

Identification

The wedge-tailed shearwater population in the south-west Pacific is comprised of all-dark birds. They have a small head, slender body, and long tail. Their plumage is blackish-brown, with the feathers of the back and wings edged in slightly lighter brown. The chin, throat and forehead are brownish-grey, with the underparts dusky brown. Pale-bellied birds (mainly North Pacific) have a dark greyish-brown head, nape and upperparts, grading into the white chin and throat. Their underparts are mainly white with variable grey-brown mottling on the sides of the breast, flanks and undertail. The underwings are white with a broad dark trailing edge. The slender bill is dark slate grey, and the legs are pale flesh-coloured. The sexes are alike with no seasonal variation. In flight, wedge-tailed shearwaters alternate fast wing-beats with long glides.

Voice Specialist

On breeding grounds, wedge-tailed shearwaters make a wailing moan ‘ka-whooo-ahh’. Colonies produce a cacophony of calls.

Distribution and habitat

The wedge-tailed shearwater is a widely distributed migratory species throughout the Pacific and Indian oceans. It breeds on many islands including Kermadec (New Zealand), Norfolk, Lord Howe, Fiji, Tonga, Samoa, Pitcairn, New Caledonia, Vanuatu, Solomon, Johnston Atoll, Christmas (Kiribati), Marshall, Caroline, Bonin, the Hawaiian archipelago, Madagascar, the Seychelles, and Reunion and islands off the west and east coasts of Australia and the west coast of Mexico.

Wedge-tailed shearwaters are pelagic in the tropical and subtropical Pacific and Indian oceans, mainly between 35°N and 35°S. Southern hemisphere birds migrate north of the Equator, with the Kermadec population migrating to the south-east North Pacific during the austral winter. Wedge-tailed shearwaters rarely reach waters off the New Zealand mainland, with a few recorded at sea between Cape Reinga and East Cape, or beach-wrecked birds on North Island coasts.

Population

The wedge-tailed shearwater has an estimated global population of 5 million+ birds, including an estimated 50,000+ pairs that breed at the Kermadec Islands (Raoul, Meyer and Herald Islets, Macauley, Curtis, Cheeseman and L’Esperance Rock).

Threats and conservation

Although it has a large estimated global population, the wedge-tailed shearwater may be declining in some areas due to changes in its food supply possibly linked to declining tuna stocks and changes in sea temperature. In 2002, unusually high sea-surface temperatures in the Great Barrier Reef were accompanied by reduced provisioning, decreased growth rates and reproductive failure of wedge-tailed shearwaters in the region. Over-exploitation through poaching or persecution is also likely to reduce some populations. Wedge-tailed shearwaters are vulnerable to predation by invasive species, including feral cats, rats and pigs, which kill and eat birds and eggs.

The bulk of the Kermadec Islands population breeds on Macauley Island where introduced Pacific rats were eradicated in 2006, and also on smaller islands (e.g. Curtis Island and the Herald Islets) that never had introduced predators. In contrast, the breeding population on Raoul Island (by far the largest island in the group) is a fraction of the immense numbers present there 100 years ago. The almost complete extirpation of wedge-tailed shearwaters on Raoul Island was due to predation by introduced cats and rats. Wedge-tailed shearwaters were rare on Raoul Island by 1966-1967, and no evidence for their presence was found in 1993-1994 (though a single bird was found in a burrow there in April 1998). Feral goats were eradicated from Raoul Island in 1984, followed by feral cats and rats in 2002. In 2008, 13 active wedge-tailed shearwater burrows were found on Raoul Island, signalling the start of a return to their former stronghold.

The IUCN Red List classifies wedge-tailed shearwater as Least Concern. The Department of Conservation classifies it as Relict (B; range restricted, and secure overseas), meaning that it remains numerous but now occupies less than 10% of its original range, reflecting the human-induced extirpation of the formerly enormous Raoul Island population.

Breeding

Wedge-tailed shearwaters breed from October to May at the Kermadec Islands, and are absent June-September. Breeding birds arrive from October with mating taking place during October-November. They are monogamous, and lay their single large (67 x 43 mm) white egg in December. Nests are usually in a burrow up to 2.5 m long, but may be on the ground under an overhanging rock, in a small cave, or under vegetation. Incubation takes 50-54 days and is shared by both adults. Eggs hatch in early February. The chicks grow much larger than adults during the nestling period, increasing to c.560 g before slimming down to c.430 g at fledging. Adults typically depart on migration 1-2 weeks before the chicks fledge around mid-May, at about 90 days-old. Wedge-tailed shearwaters start breeding at about 4 years-old.

Behaviour and ecology

The wedge-tailed shearwater is an annual breeder in dense colonies. They are usually solitary at sea, but sometimes form small feeding flocks or rafts at sea off colonies. Both adults dig the burrow using their bill and feet. After mating, both birds return to sea to feed for several weeks before egg-laying and incubation.

Food

Wedge-tailed shearwaters feed mainly on fish, including flying fish, plus squid, insects, jellyfish and prawns. They often form feeding flocks over tuna or dolphins, which drive smaller fish to the surface, where wedge-tailed shearwaters may form feeding aggregations with sooty and white terns, noddies and boobies. They are also attracted to fishing vessels. Wedge-tailed shearwaters forage by contact-dipping, surface-seizing and sometimes deep plunging, exceptionally diving up to 66 m below the surface (less than 14 m is typical).

Maa Hoagulha- Flash-footed Shearwater

Flesh-footed shearwaters are medium to large-sized dark seabirds with long powerful hooked bills. They nest on offshore islands around northern New Zealand and in Cook Strait. Flesh-footed shearwaters are attracted to boats and are commonly observed over inshore seas, especially in the Hauraki Gulf and Bay of Plenty. They often sit behind recreational fishing boats and dive to retrieve bait and discarded fish scraps. Their persistence in taking bait from fishing lines puts them into conflict with both recreational and commercial fishers, often with fatal consequences. After breeding, the birds migrate to the North Pacific Ocean where they spend the northern summer in the seas off eastern Japan. The return migration is through the central Pacific Ocean.

Identification

The flesh-footed shearwater is a medium to large-sized dark brown shearwater (tube-nosed seabird) with long relatively broad wings and a long pointed tail in flight. They are uniformly dark plumaged, contrasting with the pink-white bill and white-flesh coloured legs. In the hand, the pale bill (38-45 mm long) has a sharp hook.

Voice: the calls of flesh-footed shearwaters resemble cats fighting, with loud wailing and moaning.

Similar species: dark morph wedge-tailed shearwaters are very similar but have longer tails and all-dark bills. Black petrel (which co-occurs with flesh-footed shearwater in the outer Hauraki Gulf and adjacent deeper water) is larger and heavier-looking, with darker black plumage, a creamy-white (cf. pinkish) bill and black legs.

Distribution and habitat

Flesh-footed shearwaters nest on 15 islands around northern New Zealand and in Cook Strait, with the largest colonies on the Chickens and Mercury groups plus Ohinau and Karewa Islands. Elsewhere, there are colonies on Lord Howe Island, islands off Western Australia and on Ile St Paul in Indian Ocean. The breeding burrows are normally dug on well drained sites with sandy or clay soils, and under tall forest or low coastal shrubs such as taupata or kanuka. The birds are powerful diggers and dig burrows 1-4 m in length. Flesh-footed shearwaters forage over warmer water north of 43°S, either over shallow inshore seas or over deep water beyond the continental shelf. After the breeding season, they migrate north past Fiji and Tonga to complete the annual feather moult in the North Pacific Ocean off Japan.

Population

Recent surveys in New Zealand have found far fewer flesh-footed shearwater pairs than expected. A survey of 8 major colonies found 8000 pairs and further 3000 pairs are estimated to occur on Middle Island. The total New Zealand population is therefore less than 12,000 pairs. Declines have also taken place on Lord Howe Island, and so the species is now considered threatened.

Threats and conservation

Flesh-footed shearwaters are largely free of land-based threats in New Zealand. All of the breeding sites except one are now cleared of introduced predators or have active pest control happening. However, at sea, the situation is not as rosy. Flesh-footed shearwaters are regularly caught as bycatch in several commercial fisheries [see New Zealand commercial fisheries by-catch information here]. They are also frequently caught by recreational fishers; although most such birds are released with no or minor injuries, there is disturbing evidence that many flesh-footed shearwaters are severely injured or killed by fishers hitting them to keep them away from fishing baits. Flesh-footed shearwaters were vulnerable in the 2011 Rena oil spill and are at risk in future oil spills. The Lord Howe Island shearwater population has encountered problems with plastics being ingested by the birds and this same threat may also exist in the New Zealand populations. Flesh-footed shearwaters also feed close inshore in eastern Japan and some birds may have been exposed to land-based pollutants and raised levels of radioactivity in the ocean after the 2011 tsunami and Fukushima nuclear reactor plant explosions. The conservation status of this species was changed from declining to nationally vulnerable in 2013.

Breeding

Flesh-footed shearwaters breed from September to May with the single large (69 x 46 mm) white egg laid from early to mid-December and hatching in late January or early February. Chicks depart in May. The egg is laid in a lightly-lined nest at the back of burrows (1-4 m long). Flesh-footed shearwaters can be sensitive to human disturbance and sometimes temporarily desert nests by day after handling, although the birds normally return to the nest within a day or two. Egg-chilling resistance in this species (a trait common to other petrels and shearwaters) allows the egg to continue developing with little impact on breeding success. Flesh-footed shearwater breeding success is affected by oceanic conditions, with good years dependent on ocean currents bringing lots of small fish to seas near the colonies. Immature flesh-footed shearwaters start to return to colonies as 4 year-olds and first start breeding at 5-6 years of age.

Behaviour and ecology

Flesh-footed shearwaters are nocturnally active at breeding grounds. The first birds start flying over the islands soon after sunset and birds can come ashore throughout the night. Prospecting birds are very noisy on the surface at night, calling from burrow entrances and in flight over the colony. The birds are especially noisy in the period just before dawn and on large colonies it is nearly impossible for people to sleep through the dawn exodus period. The calls resemble those of cats having a huge fight. At sea, the birds range widely away from the breeding colonies, foraging over the continental shelf. They mainly forage around the North Island, but also regularly north and west towards Norfolk and Lord Howe Islands. They are often seen from ships and boats, and will follow boats hoping for fish scraps or offal to be discharged. Flesh-footed shearwaters are trans-equatorial migrants, flying north directly after breeding via the top of the Tasman Sea or past Fiji and Tonga before heading north-west at the equator to reach the seas off Japan. They return by heading into the central North Pacific and then south past Hawaii and down into the north Tasman Sea or past Tonga and the Kermadec Islands.

Food

Flesh-footed shearwaters specialise on small fish caught by shallow dives into shoals, or occasional deeper dives reaching 30 m in depth. They sometimes eat small squid. Chicks are fed 80-90 g meals every 2-3 days on average. Activity sensors applied to the shearwaters legs suggest most feeding occurs during the hours of daylight.

Amazing facts

Until 15 to 20 years ago they Shearwater were not regarded as capable divers, but then scientists began to attach depth sensitive capillaries to birds to record their maximum depths on trips out to feed. Astonishing depths began to be recorded. The king of diving is the Short-tailed Shearwater, which has been recorded diving to 70 m below the surface, with average trip depths of 58 m. Dhivehi hoagulha or Audubon’s Shearwaters, which have made it to 35 m, Sooty Shearwaters (max 67 m, av 39 m) and bodu hoagulha or Wedge-tailed Shearwaters (max 66 m).

Record breaker – Short tailed Shearwater

 

Reference

http://maldivesseabirds.blogspot.com/

http://www.vermillionmaldives.com/maldives-birds.htm

https://animalcorner.co.uk/animals/audubons-shearwater/

http://www.britannica.com/animal/Peruvian-diving-petrel

http://www.britannica.com/animal/shearwater

http://nzbirdsonline.org.nz/species/sooty-shearwater

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s