Beach thick-knee (Esacus giganteus)

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Beach thick-knee fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Beach thick-knee description

Also known as the beach stone-curlew, the beach thick-knee (Esacus giganteus) is a very large and distinctive shorebird with a massive, thick, slightly upturned beak, a large head, a stocky body and sturdy legs ^{(2) (3) (4) (5)}. Its common name comes from its swollen-looking ‘knees’, which actually correspond to its ankle joints ^{(5) (6)}.

The beach thick-knee’s head is strikingly marked with white stripes across an otherwise black face ^{(2) (3) (4) (5)}, and it has large, bright yellow eyes ^{(2) (3) (5)}. The top of the head is grey-brown, the throat is white ^{(2) (3)}, and there is a yellow patch at the base of the beak, which is black ^{(2) (3) (5)}. The upperparts of the beach thick-knee are grey-brown, while the breast is paler grey-brown and the belly is whitish ^{(3) (4) (5)}. This species has a short, olive-brown tail ^{(3) (4)}.

The beach thick-knee has long, broad wings ^{(2) (3) (4)} which show distinct ‘fingers’ at the ends when the bird is in flight ^{(2) (3)}. This species’ wings are largely pale grey to white, with dark front and back edges. The shoulders are marked with blackish-brown and white stripes ^{(3) (4)}, and there are white patches on the black outer primary feathers ⁽³⁾. The beach thick-knee’s legs are generally brownish to greenish-yellow ⁽³⁾, and its feet are slightly webbed and have no hind toe ⁽⁶⁾.

Male and female beach thick-knees are similar in appearance ⁽³⁾, while juveniles are distinguished by their slightly duller beak, eyes and legs, and by the buff fringes to the feathers on their upperparts ^{(2) (3)}.

The beach thick-knee generally calls at night with a mournful-sounding ‘wee-loo’ ^{(3) (4) (5)}. It also gives a yapping ‘quip’, ‘peep’ or ‘weal’ as an alarm call ^{(3) (5)}.

Also known as

Australian stone plover, Australian stone-plover, beach curlew, beach stone-curlew, large-billed stone plover, reef thick-knee.

Synonyms

Burhinus giganteus, Burhinus neglectus, Esacus magnirostris, Esacus neglectus.

Size

Length: 53 - 57 cm ^{(2) (3)}

Wingspan: up to 1.1 m ⁽⁴⁾

Weight

870 - 1,130 g ⁽²⁾

Beach thick-knee biology

The beach thick-knee is usually seen alone or in pairs, although it occasionally occurs in small groups ^{(3) (4)}. It normally hunts at night or at dawn and dusk, slowly stalking its prey or making rapid lunges at it ^{(2) (3) (4)}, and sometimes probing its beak into mud, sand or short grass ⁽²⁾. The beach thick-knee mostly forages among rocks, on intertidal areas of beaches and estuaries, or among mangroves ^{(2) (4) (5)}. If disturbed, it often flies out to sea ⁽²⁾, moving with slow, heavy wing beats ⁽³⁾.

The diet of the beach thick-knee consists predominantly of crabs, as well as other marine crustaceans ^{(2) (3) (4) (5) (8)}. This species uses its massive beak to hammer open its prey ^{(2) (5)}, and it sometimes washes its food before swallowing it ⁽⁵⁾.

The beach thick-knee is thought to be monogamous ⁽²⁾, and it breeds in isolated pairs either at the back of a large beach, or among mangroves, grass, on sandbanks or on islands ^{(2) (4) (5)}. Pairs may nest in the same area for several years ^{(2) (8)}. The breeding season generally runs from September to November in temperate parts of Australia ^{(2) (5)}, but further north the beach thick-knee may breed between July and November ⁽²⁾.

The beach thick-knee’s nest consists of a shallow scrape in the ground ^{(2) (4)} and is not lined, although it may be surrounded by a ring of twigs and dead leaves ⁽²⁾. Only one egg is laid, but the female beach thick-knee may lay another if the first is lost. The egg is incubated for about 30 days. Both the adults help care for the young, which is able to fly at about 12 weeks old, but does not become independent until it is 7 to 12 months old ^{(2) (4) (5)}. The eggs of the beach thick-knee are vulnerable to predators such as cats, dogs and birds of prey, and may also be lost in high tides ⁽²⁾.

Beach thick-knee range

The beach thick-knee occurs around coastlines from the Andaman Islands and the Malay Peninsula, through Indonesia, the Philippines and New Guinea, to northern and eastern Australia and islands in the southwest Pacific ^{(2) (4) (7) (8)}.

Although the beach thick-knee does not migrate, individuals are occasionally seen quite a long way outside of their normal range ^{(2) (7) (8)}.

Beach thick-knee habitat

An exclusively coastal bird, the beach thick-knee, as its name suggests, is found on a variety of sandy, muddy and rocky beaches ^{(2) (4) (5) (8)}. It particularly favours beaches near mangroves and estuaries ^{(5) (8)}, and will also use offshore sandbars, river mouths and coral reefs ^{(2) (4) (5)}.

Beach thick-knee status

The beach thick-knee is classified as Near Threatened (NT) on the IUCN Red List ⁽¹⁾.

Beach thick-knee threats

The beach thick-knee is a widespread species, but its overall population is relatively small ⁽⁷⁾. Potential threats to this unusual bird include habitat loss, coastal development, predation by introduced cats and dogs, nest trampling by feral pigs, and human disturbance at its nesting beaches ^{(2) (5) (7) (8) (9)}. Its slow breeding rate also puts the beach thick-knee at risk ⁽²⁾.

In the mid-20th century the beach thick-knee’s range expanded southwards into New South Wales in Australia ^{(2) (7) (8)}, but disturbance, habitat loss and predation have now led this species to be classified as ‘Critically Endangered’ in this state ⁽⁴⁾.

Beach thick-knee conservation

The beach thick-knee is listed on the Environment Protection and Biodiversity Conservation Act, which provides a framework for the conservation of threatened species and environments in Australia ⁽⁹⁾. However, no other specific conservation measures are currently known to be targeted at this large shorebird ⁽⁷⁾.

Various conservation actions have been proposed to help protect the beach thick-knee, including population monitoring and keeping a record of nesting beaches, particularly where human disturbance is a problem ^{(7) (8)}. It will also be important to control domestic cats and dogs, to put fences around known nesting sites, and to prevent access to certain beaches by humans and dogs ^{(4) (7) (8)}. Undisturbed nesting habitat should be protected from development, and measures should be taken to increase public awareness of the beach thick-knee, for example by putting up signs on beaches ⁽⁴⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

Find out more about the beach thick-knee and its conservation:

• BirdLife International - Beach thick-knee:
  http://www.birdlife.org/datazone/speciesfactsheet.php?id=30066
• Birds in Backyards - Beach stone-curlew:
  http://www.birdsinbackyards.net/species/Esacus-magnirostris
• Queensland Wader Study Group - Beach stone-curlew:
  http://www.waders.org.au/about-waders/shorebird-identification/waders-regularly-seen-in-australia/beach-stone-curlew/

More information on conservation in Australia:

• BirdLife Australia:
  http://www.birdlife.org.au/
• Australian Conservation Foundation:
  http://www.acfonline.org.au/
• Australian Wildlife Conservancy:
  http://www.australianwildlife.org/

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Glossary

Crustaceans

Diverse group of animals with jointed limbs and a hard chitinous exoskeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.

Feral

Previously domesticated animals that have returned to a wild state.

Incubate

To keep eggs warm so that development is possible.

Intertidal

Pertaining to the intertidal zone, the region between the high tide mark and low tide mark.

Monogamous

Having only one mate during a breeding season, or throughout the breeding life of a pair.

Primary feathers

In birds, the main flight feathers projecting along the outer edge of the wing.

References

1. IUCN Red List (April, 2013)
   http://www.iucnredlist.org/
2. del Hoyo, J., Elliott, A. and Sargatal, J. (1996) Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona.
3. Hayman, P., Marchant, J. and Prater, T. (2011) Shorebirds. A&C Black Publishers, London.
4. NSW Government, Office of Environment & Heritage - Beach stone-curlew profile (April, 2013)
   http://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=10280
5. Birds in Backyards - Beach stone-curlew (April, 2013)
   http://www.birdsinbackyards.net/species/Esacus-magnirostris
6. Burton, M. and Burton, R. (2002) International Wildlife Encyclopedia. Third Edition. Marshall Cavendish, New York.
7. BirdLife International - Beach thick-knee (April, 2013)
   http://www.birdlife.org/datazone/speciesfactsheet.php?id=30066
8. Garnett, S.T. and Crowley, G.M. (2000) The Action Plan for Australian Birds 2000. Environment Australia, Canberra. Available at:
   http://www.environment.gov.au/biodiversity/threatened/publications/action/birds2000/index.html
9. Department of Sustainability, Environment, Water, Population and Communities (2013) Esacus magnirostris. In: Species Profile and Threats Database. Department of Sustainability, Environment, Water, Population and Communities, Canberra. Available at:
   http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=891