THICK-KNEES Burhinidae
The Thick-knees are a small family of terrestrial waders, found mostly in drier country in tropical lands around the world. Other names used for these birds are "Stone-Curlews" or "Dikkops." Four species occur in Africa or the Middle East; two of them widely in Africa south of the Sahara: Water Dikkop (left) and Spotted Dikkop (right; a fine shot © Dale & Marian Zimmerman). Both of these photos were taken in autumn 1981; mine on my first trip to Kenya while the Zimmerman's were then old African hands. Ironically, Spotted Dikkop has proven to be the only thick-knee I've not seen in the world. It is very much a nocturnal species, hiding under bushes during the day, while the Water Dikkop is often found diurnally, standing around little mud-holes or along slow moving rivers. Both birds show the characteristic long legs, big eyes, heavy bills, and cryptic plumage of this group.
Two photos by Barry McLaughlin from west Africa complete the subSarahan species: his Spotted Dikkop (below left) really shows the "big-eyed" look of these birds (and especially of this nocturanl species) while two Senegal Dikkop (below right) rest in the shade of mangrove roots. This species replaces Water Dikkop in the Sahel, stretching across Africa from Senegal and The Gambia to n. Kenya. It lacks the white bar above the pale gray wing panel.

Another species, Stone-Curlew Burhinus oedicnemus, sometimes called Eurasian Thick-knee, is widely if thinly spread across the Western Palearctic (including north Africa) and east through India to Indochina. It may be the best known species to those living in the Old World, but is actually a challenge to locate for an American birder. Nesting locales in England, for example, are quite few and sometimes information is not readily forthcoming. In Bharatpur reserve, India, the species is found in patches of dry woodland and hard to find without specific details. This species has declined in many areas due to human disturbance or habitat loss. Bush Thick-knee B. grallarius is a rather similar bird restricted to Australasia.
 

Some (e.g, Sibley & Monroe 1990) place all nine species of thick-knees in one genus (Burhinus) but a more recent work (Hume 1996) divides them into two genera (Burhinus, Esacus). The latter genus is used for two closely related birds that are more heavily shoreline foragers than many thick-knees: Beach Thick-knee (below in an evocative shot © Will Betz) and Great Thick-knee (right; shown with grazing Chital Cervus axis in Corbett Nat'l Park, India).
Both Esacus thick-knees feed primarily on crabs; the Beach Thick-knee dines on them almost exclusively. Great Thick-knee occurs from Iran to s. China; Beach Thick-knee is found along the shores of Australasia, Indonesia, the Philippines, and some southwest Pacific islands.

At one time the Burhinidae were considered related to Bustards (Otididae) in the order Gruiformes, but all the recent evidence, both biochemical and structural, shows that they are a distinct group of waders in the Charadriformes (Sibley & Monroe 1990, Hume 1996). It is not really known exactly what other birds are most closely related. Many of their dry country adaptations appear to be the result of convergent evolution (which is what made them superficially similar to Bustards); other features suggest that Esacus thick-knees could be related to Crab-Plover (Dromadidae) but this also may be convergent evolution, given the reliance of each on crabs.

Some species (e.g., Stone-Curlew) are migratory (at least in some of the population) but most are resident birds, moving in response to dry or wet conditions. All thick-knees are silent by day but become very vocal after dark, with loud, wailing calls or accelerating series of curlew-like "cur-leeee" calls that die away into the night air. The Peruvian Thick-knee (below), one of two species in the New World, is known locally as "Huerequeque," a transliteration of its calls (Hume 1996).

Peruvian Thick-knee is a terrestrial bird of very dry country along the arid coastal plain of s. Ecuador and Peru. My marginal photo (above) shows just how cryptic they can be among the dirt clods. The remaining New World species is Double-striped Thick-knee B. bistriatus, and it ranges from e. Mexico to the northern coast of South America, and in open llanos of Venezuela and n. Brazil.

All the Burhinus thick-knees are social birds and can sometimes be found in flocks of a dozen or so. They are largely nocturnal, and both feeding and social displays take place mostly at night. During the day, one encounters them generally standing around motionless, and often inconspicuously, in the shade of low vegetation. Because of these behaviors, it is not usually very dramatic to see a thick-knee. Their world begins mostly after dark.

Photos: The Water Dikkop Burhinus vermiculatus was found along the shores of Lake Jipe, Kenya, in Nov 1981. Dale & Marian Zimmerman photographed the uppermost Spotted Dikkop B. capensis in Amboseli Nat'l Park, Kenya, in Sep 1981. Barry McLaughlin took the other Spotted Dikkopat a place called Barra, near Farrafenni, The Gambia, on 21 Nov 2003, and he photo'd the two Senegal Dikkop B. senegalensis near Darsalami, The Gambia, on 17 Nov 2003. Will Betz captured the Beach Thick-knee Esacus magnirostris in the Auri Islands, Irian Jaya, Indonesia. The three Great Thick-knee E. recurvirostris foraging next to Chital (Spotted Deer) were in Corbett Nat'l Park, Uttar Pradesh, India, on 15 Mar 2001. The Peruvian Thick-knee B. superciliaris was photographed near Linchon, Dept. Lima, Peru, on 11 June 1987. All photos © 2003 Don Roberson, except those attributed to Dale & Marion Zimmerman, to Barry McLaughlin, and to Will Betz, who holds those copyrights and which are used with permission; all rights reserved.

Bibliographic note:

There is no specialized "family book" of which I'm aware, although this family is often covered in books that include shorebirds and allies (e.g., Hayman et al. 1986, briefly reviewed on the sandpipers page). An excellent overview to the family, with a set a very impressive photos, is in Hume (1996).

Literature cited:

Hayman, P., J. Marchant & T. Prater. 1986. Shorebirds: An Identification Guide to the Waders of the World. Croom Helm, London.

Hume, R.A. 1996. Family Burhinidae (Thick-knees), pp. 348-363 in del Hoyo, J., Elliott, A., & Sargatal, J., eds. Handbook of the Birds of the World. Vol. 3. Lynx Edicions, Barcelona.

Sibley, C.G., and B.L. Monroe. 1990. Distribution and Taxonomy of the Birds of the World. Yale Univ., New Haven CT.

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Page created 7 Dec 2003, revised 8 Dec 2003