Crab Plover (Dromas ardeola

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[edit] The Crab Plover (Dromas ardeola) Paykull, 1805

The crab plover (Dromas ardeola) is a large, long-legged, pied, exclusively marine wader.

[edit] Taxonomy

The Crab Plover (Dromas ardeola) is related to the waders, but is 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 pratincoles, while others have considered it closer to the auks and gulls. It is the only member of the genus Dromas. Sibley & Monroe, relying heavily on DNA-DNA hybridization evidence, considered carb plover just a very odd courser (Glareolidae). Most taxonomists elevate it to its own monotypic family. In fact Jehl divided all the waders into three groups on the basis of his study of downy chicks: the ja├žanas & painted-snipes, the Crab Plover, and then all the remaining families. This division -- which elevates the Crab Plover to its own superfamily -- highlights its uniqueness and is considered the "standard" approach at present.

Class: Aves
Order: Charadriiformes
Family: Dromadidae
Genus: Dromas
Species: Dromas ardeola, Paykull, 1805

[edit] Distribution

Crab plover lives on coasts of Indian Ocean. It breeds on shore of N.W. Indian Ocean, Persian Gulf and Red Sea, and Somalia in April - July. Non breeders range Kenya, Tanzania and Madagascar, W India and N Sri Lanka.

[edit] Physical Characteristics

  • Crab plover is a strikingly patterned large wader. When head sunk on shoulders, large head and massive bill (2 to 2.30 inches) gives an impression of a long-legged gull when seen at a distance.
  • It has a massive straight black bill. It's bill is unique among waders, and specialized for eating crabs. It has a disproportional large head, either all white or with at most dark streaking on rear crown and nape.
  • Plumage is white, except for black on its back and in the primary feathers of the wings, conspicuous in flight. Eyes are large and dark. Tail is grayish, long legs are bluish grey, with partially webbed toes.
  • Both sexes are similar. Juvenile lacks distinctive adult pattern, with grey-brown wing coverts, black-brown crown and hind neck, silvery grey mantle and browner tail. It lacks also massive bill and it has shorter legs. They attain adult plumage when they are 15 months old.

[edit] Habitat

Crab plover lives on sandy coastlines and islands, intertidal sandflats and mudflats, estuaries, lagoons, exposed coral reefs, and rocky shorelines. It's also found in sand dunes when it is breeding.

[edit] Diet

Crab plover feeds primarily on crabs, but also crustaceans, small mollusks, marine worms and intertidal invertebrates. They feeds by picking and probing and slow stalking, crabs are stabbed with open bill, then crushed and eaten.

[edit] Behavior

Crab plover has a characteristic behavior: it rests on flat tarsi, like sit on the ground. It feeds with plover-like "run-stop-run-dip-action". Most often feeds in flocks on mudflats at low tide, or in shallow water. It's most active at dusk and at night. Feeds by picking and probing, and slow stalking. Crab are stabbed which open bill, then crushed and eaten. At high tide, Crab plover use roosts with other shorebirds, or wade out among flamingos. Crab plover's call is a barking, repeated "ka-how, ka-how..." and on breeding grounds, a sharp, whistling "kew-ki-ki" or "ki-twek". They are noisy birds, calling frequently on their breeding and wintering areas. Crab plover flies strongly, with wing beats rather slow. Legs are projected well beyond tail in flight.

[edit] Breeding

Colonial nesting, an aspect in the nesting behavior of crab plover which has a strong bearing on their conservation, is much more characteristic of seabirds, be they on cliffs or on islands, than of waders. Only a dozen or so crab plover breeding colonies are known and several of those that have been pinpointed have not been visited in recent years. All are on islands and conservation is effectively an 'all or nothing' act: an entire population can be saved, or just as easily lost, in one fell swoop. The same applies in the winter quarters, albeit to a lesser degree, because they remain sociable year-round, feeding in a limited number of particularly favored areas. Its distribution is very localized. Indeed, only nine nesting colonies are known in the entire world! Compared with the majority of the worlds' coastal breeding waders, crab plovers have a very restricted breeding range, stretching from Somalia in the west via the coast of Arabia to Iran in the east. Most waders with such a characteristic are confined to one, or a few, islands and several have become very rare while others are now extinct. The Crab Plover is unique among waders by nesting in burrows that it digs itself. Some ornithologists have noted that this behavior is like auks. They breeds colonially in burrows set close together, forming honeycomb effect in sandy areas in Apr-July. Nest is unlined chamber at end of burrow 100-250 cm long, in sandy substrate. They normally lay one egg and chicks have plain grey down, fed by parents in nest chamber.

[edit] References

  1. Hayman, P., J. Marchant, T. Prater. 1986. Shorebirds: an identification guide to the waders of the world. London: Croom Helm, Ltd.
  2. The Clements Checklist of Birds of the World: James F. Clements, Jared Diamond, John W. Fitzpatrick.
  3. Wetlands International Waterbird Population Estimates - Fourth Edition.
  4. Ali, S. & Ripley, D. (1964-74 ) Handbook of the Birds of India & Pakistan (Vols. 1-10). Bombay: OUP
  5. Grimmet, R Inskipp, T., & Inskipp, C. (1998) Birds of the Indian Subcontinent. UK: A&C Black.
  6. Inskipp, T. et al. (1996) An Annotated Checklist of the Birds of the Oriental Region. Sandy, UK: OBC.
  7. Kazmierczak, K. & van Perlo, B. (2000) A Field-Guide to the Birds of the Indian Subcontinent. UK: Pica Press
  8. BirdLife International (2004).
  9. IUCN Red List of Threatened Species. IUCN 2006
  10. Peterson, R.T., Mountfort, G. & Hollom, P.A.D. (1993) Collins Field Guide- Birds of Britain and Europe.

Author: Arpit Deomurari

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