Crab Plover
Encyclopedia
The Crab-plover or Crab Plover (Dromas ardeola) is a bird
related to the wader
s, but sufficiently distinctive to merit its own family Dromadidae. Its relationship within the Charadriiformes
is unclear, some have considered it to be closely related to the thick-knees, or the pratincole
s, while others have considered it closer to the auk
s and gull
s. It is the only member of the genus Dromas and is unique among wader
s in making use of ground warmth to aid incubation of the eggs
.
, but has very long grey legs and a strong heavy black bill similar to a tern
. Its black-and-white plumage and long-necked upright posture with heavy bill makes it distinctive and unmistakable. Its bill is unique among waders, and specialised for eating crabs. It has partially webbed toes. The plumage is white except for black on its back and in the primary feathers of the wings. They are noisy birds, calling frequently on their breeding sites and in their wintering grounds. The usual call is a ka similar to that of the Bar-tailed Godwit but repeated rapidly. Flocks may produce a whinnying sound that rises and at in the breeding season produce whistling kew-ki-ki notes.
Males and females are not easily distinguished but males have a heavier and longer bill. Juveniles have the black on the mantle, greyish and remain in this plumage for a year. Flocks fly in lines or "V" formations.
The Crab Plover is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA
) applies.
, where it feeds on crab
s and other small animals. They are gregarious and will feed in large groups, at night and during dawn and dusk as well as during the day; this crepuscular
and nocturnal behaviour is more common during the breeding season. They breed around the Arabian Sea
of Pakistan
, Gulf of Oman and the Persian Gulf
, Red Sea
and Somalia
in the months of April to July then disperse across the Indian Ocean in August as far as the Andaman Islands
and Sri Lanka
in the east and Tanzania
and Madagascar
.
s in sandy banks. In the Red Sea region, the breeding season begins around the middle of May. It is a colonial
breeder, nesting in colonies as large 1500 pairs. It lays one white egg
, occasionally two, which are large for its body size. The nest burrow temperature is optimal due to solar radiation and the parents are able to leave the nest unattended for as long as 58 hours. The chicks are also unique for the usually nidifugous
waders in being unable to walk
and remain in the nest for several days after hatching, having food brought to them. Even once they fledge
they have a long period of parental care afterwards. Both males and females take care of the young.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
related to the wader
Wader
Waders, called shorebirds in North America , are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas , gulls , terns , skimmers , and auks...
s, but sufficiently distinctive to merit its own family Dromadidae. Its relationship within the Charadriiformes
Charadriiformes
Charadriiformes is a diverse order of small to medium-large birds. It includes about 350 species and has members in all parts of the world. Most Charadriiformes live near water and eat invertebrates or other small animals; however, some are pelagic , some occupy deserts and a few are found in thick...
is unclear, some have considered it to be closely related to the thick-knees, or the pratincole
Pratincole
The Pratincoles or Greywaders are a group of birds which together with the coursers and Egyptian Plover make up the family Glareolidae. They have short legs, very long pointed wings and long forked tails....
s, while others have considered it closer to the auk
Auk
An auk is a bird of the family Alcidae in the order Charadriiformes. Auks are superficially similar to penguins due to their black-and-white colours, their upright posture and some of their habits...
s and gull
Gull
Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...
s. It is the only member of the genus Dromas and is unique among wader
Wader
Waders, called shorebirds in North America , are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas , gulls , terns , skimmers , and auks...
s in making use of ground warmth to aid incubation of the eggs
Bird egg
Bird eggs are laid by females and incubated for a time that varies according to the species; a single young hatches from each egg. Average clutch sizes range from one to about 17...
.
Description
This bird resembles a ploverPlover
Plovers are a widely distributed group of wading birds belonging to the subfamily Charadriinae. There are about 40 species in the subfamily, most of them called "plover" or "dotterel". The closely related lapwing subfamily, Vanellinae, comprises another 20-odd species.Plovers are found throughout...
, but has very long grey legs and a strong heavy black bill similar to a tern
Tern
Terns are seabirds in the family Sternidae, previously considered a subfamily of the gull family Laridae . They form a lineage with the gulls and skimmers which in turn is related to skuas and auks...
. Its black-and-white plumage and long-necked upright posture with heavy bill makes it distinctive and unmistakable. Its bill is unique among waders, and specialised for eating crabs. It has partially webbed toes. The plumage is white except for black on its back and in the primary feathers of the wings. They are noisy birds, calling frequently on their breeding sites and in their wintering grounds. The usual call is a ka similar to that of the Bar-tailed Godwit but repeated rapidly. Flocks may produce a whinnying sound that rises and at in the breeding season produce whistling kew-ki-ki notes.
Males and females are not easily distinguished but males have a heavier and longer bill. Juveniles have the black on the mantle, greyish and remain in this plumage for a year. Flocks fly in lines or "V" formations.
The Crab Plover is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA
AEWA
The Agreement on the Conservation of African-Eurasian Migratory Waterbirds is the largest of its kind developed so far under the Bonn Convention. It was concluded on 16 June 1995 at The Hague, the Netherlands and entered into force on 1 November 1999 after the required number of at least fourteen...
) applies.
Range
It is resident on the coasts and islands of the Indian OceanIndian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
, where it feeds on crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s and other small animals. They are gregarious and will feed in large groups, at night and during dawn and dusk as well as during the day; this crepuscular
Crepuscular
Crepuscular animals are those that are active primarily during twilight, that is during dawn and dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is, thus, in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright...
and nocturnal behaviour is more common during the breeding season. They breed around the Arabian Sea
Arabian Sea
The Arabian Sea is a region of the Indian Ocean bounded on the east by India, on the north by Pakistan and Iran, on the west by the Arabian Peninsula, on the south, approximately, by a line between Cape Guardafui in northeastern Somalia and Kanyakumari in India...
of Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
, Gulf of Oman and the Persian Gulf
Persian Gulf
The Persian Gulf, in Southwest Asia, is an extension of the Indian Ocean located between Iran and the Arabian Peninsula.The Persian Gulf was the focus of the 1980–1988 Iran-Iraq War, in which each side attacked the other's oil tankers...
, Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
and Somalia
Somalia
Somalia , officially the Somali Republic and formerly known as the Somali Democratic Republic under Socialist rule, is a country located in the Horn of Africa. Since the outbreak of the Somali Civil War in 1991 there has been no central government control over most of the country's territory...
in the months of April to July then disperse across the Indian Ocean in August as far as the Andaman Islands
Andaman Islands
The Andaman Islands are a group of Indian Ocean archipelagic islands in the Bay of Bengal between India to the west, and Burma , to the north and east...
and Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
in the east and Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...
and Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
.
Habits
The Crab Plover is unusual for waders in that it nests in burrowBurrow
A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...
s in sandy banks. In the Red Sea region, the breeding season begins around the middle of May. It is a colonial
Bird colony
A bird colony is a large congregation of individuals of one or more species of bird that nest or roost in close proximity at a particular location. Many kinds of birds are known to congregate in groups of varying size; a congregation of nesting birds is called a breeding colony...
breeder, nesting in colonies as large 1500 pairs. It lays one white egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
, occasionally two, which are large for its body size. The nest burrow temperature is optimal due to solar radiation and the parents are able to leave the nest unattended for as long as 58 hours. The chicks are also unique for the usually nidifugous
Nidifugous
Nidifugous organisms are those that leave the nest shortly after hatching or birth. It is derived from Latin nidus for "nest" and fugere meaning "to flee". The terminology is most often used to describe birds and was introduced by Lorenz Oken in 1916...
waders in being unable to walk
Altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
and remain in the nest for several days after hatching, having food brought to them. Even once they fledge
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
they have a long period of parental care afterwards. Both males and females take care of the young.
External links
- Crab Plover videos, photos & sounds on the Internet Bird Collection
- Images at www.naturlichter.com