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Water Thick-knee Burhinus vermiculatus Scientific name definitions

Rob Hume and Guy M. Kirwan
Version: 1.0 — Published March 4, 2020
Text last updated November 7, 2015

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Editor's Note: This is a shorter format account, originally published in HBW Alive. Please consider contributing your expertise to update and expand this account.

Identification

38–41 cm; 293–320 g. Similar to B. oedicnemus and B. senegalensis (and is syntopic with latter in parts of W Africa), but generally rather darker; broad, pale covert panel has thin white upper line on lesser coverts but lacks fine black lower edge ; bill longer and rather heavier, with less yellow at base . Unlike other Burhinus, has fine vermiculated patterns on upperparts but these are only visible at close range; in flight, has rather broad, blunt wings and short tail, with feet projecting slightly beyond tip. B. capensis lacks wingbars, unlike present species (1). Juvenile very similar to adult, but has buff spotting on grey upperwing-coverts, and more abundant vermi­culations on upperparts and tail. Race buettikoferi rather darker and browner, less grey, and has longer bill (in male 49–54 mm versus 41–46 mm in nominate) (1).

Systematics History

Editor's Note: This article requires further editing work to merge existing content into the appropriate Subspecies sections. Please bear with us while this update takes place.

Two subspecies recognized.

Subspecies


SUBSPECIES

Burhinus vermiculatus buettikoferi Scientific name definitions

Distribution
Liberia to Nigeria and Gabon; sometimes claimed to occur E to Uganda.

SUBSPECIES

Burhinus vermiculatus vermiculatus Scientific name definitions

Distribution
DRCongo E to SC Somalia, and S to E and S South Africa.

Distribution

Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Habitat

Riverbanks and lake edges , estuaries and mangroves; also undisturbed, sheltered beaches; prefers areas with some bushes for cover. Light woodland or other cover provides the shade that is essential by day. Recorded to 1500 m in Uganda (2) and 1800 m in Zambia (3).

Movement

Sedentary, apart from some local movements to avoid flooding and occasional records outside normal range in non-breeding season, e.g. in Malawi (4); birds subsequently return to exposed riversides and rocks within rivers (1) as water recedes. Species sometimes considered a vagrant to S Senegal (1), hinting at the possibility of occasional longer-distance dispersal, but other authorities treat it as a rare resident there (5).

Diet and Foraging

Feeds on insects, crustaceans and molluscs. Nocturnal and terrestrial feeder; sometimes feeds on dirt roads at night (4). Feeds by tilting forwards to grasp food in the bill. May forage more than 1 km from water.

Sounds and Vocal Behavior

Mainly vocalizes at night. A loud, rather strident but plaintive whistle, “ti-ti-ti-ti-ti-tee-tee-teee” or “pi-pi-pi-pi-pee-pee-PEE-PEE-PEE-PEE-PEE-PEE-PEE-peeu-peeeu-peeeu-peeeu-peeeu” (5), becoming more drawn-out but dying away in terminus, and often given in chorus, by pair or flock members (1); considered to be slower, more drawn-out, melancholy and less descending than that of B. senegalensis (6). Also given is a very rapid “pipipipipipipipipipi” (5).

Breeding

Season variable, but generally dry season and early rains in S Africa; Sept–Jan in Liberia (7); Jan, Apr and May in Ghana (8); Aug in Somalia (9); mainly at start of rains, Aug–Oct, in Uganda, but recorded most other months (2); Jan and Mar–Dec in Kenya; Nov in Tanzania; Jul in Gabon (10); Sep–Oct in Malawi (4); Apr and Jul–Nov (mainly Aug–Oct) in Zambia (3); Aug–Dec (exceptionally Jul–Jan) (11) in Zimbabwe and South Africa. Monogamous. Solitary. Nest is a scrape on either sandy or slightly stony ground (3), sometimes sparsely lined, often close to water (< 20 m) (11), either on shore or island (11), and near a landmark, e.g. piece of driftwood or bush, or under a palm tree on beach (Liberia) (7). Incubating bird usually quietly leaves well advance of any approaching danger or predator (11). Normally two buffy-white to sandy-yellow eggs with dark brown, black and violet-coloured markings (1), rarely one, size 44–54 mm × 32·7–39 mm (1); eggs smaller and less heavily marked than those of B. capensis (11); single brood; incubation 22–25 days, by both sexes (11). Downy young undescribed (1), but provisioned by both adults (11). No further information available.

Not globally threatened (Least Concern). Very little precise information available, partly due to secretive habits, and, in N of range, confusion with very similar B. senegalensis, with range of present species in Ethiopia still subject to elucidation due to such difficulties (12). Species still said to be locally abundant, and recorded in flocks of up to 100 birds in non-breeding season in Zambia (3); locally common in southern Africa; common in Angola; probably uncommon in Nigeria, Ethiopia (13) and Somalia (9). Precise distribution in W Africa still poorly known: only recently discovered in Benin (on coast) (6); restricted to coastal areas of Ghana, where it is a locally common resident (8); considered common in coastal Libera, where population recently estimated at > 500 pairs (7), and also in Ivory Coast (5).

Distribution of the Water Thick-knee
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  • Year-round
  • Migration
  • Breeding
  • Non-Breeding
Distribution of the Water Thick-knee

Recommended Citation

Hume, R. and G. M. Kirwan (2020). Water Thick-knee (Burhinus vermiculatus), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.watkne1.01