Thalassornis leuconotus (White-backed duck) 

Witrugeend [Afrikaans]; Idada (generic term for duck) [Xhosa]; Letata (generic term for duck) [South Sotho]; Dada, Sekwe (both are generic names for duck or goose) [Shona]; Sekwa (generic term for duck or goose) [Tsonga]; Witrugeend [Dutch]; Dendrocygne à dos blanc [French]; Weißrückenente [German]; Pato-de-dorso-branco [Portuguese]

Life > Eukaryotes > Opisthokonta > Metazoa (animals) > Bilateria > Deuterostomia > Chordata > Craniata > Vertebrata (vertebrates)  > Gnathostomata (jawed vertebrates) > Teleostomi (teleost fish) > Osteichthyes (bony fish) > Class: Sarcopterygii (lobe-finned fish) > Stegocephalia (terrestrial vertebrates) > Tetrapoda (four-legged vertebrates) > Reptiliomorpha > Amniota > Reptilia (reptiles) > Romeriida > Diapsida > Archosauromorpha > Archosauria > Dinosauria (dinosaurs) > Saurischia > Theropoda (bipedal predatory dinosaurs) > Coelurosauria > Maniraptora > Aves (birds) > Order: Anseriformes > Family: Dendrocygnidae

A small diving duck with rufous and dark-brown barring, a black bill and a diagnostic pale spot at the base of the bill, widely distributed in sub-Saharan Africa on waterbodies with emergent and floating plants. Feeds almost exclusively on seeds of aquatic plants, which it obtains from the muddy bottom by diving. 

Thalassornis leuconotus (White-backed duck)  Thalassornis leuconotus (White-backed duck) 
White-backed duck. [photo Johan van Rensburg ©] White-backed duck family. [photo Paul Zaayman ©]

Distribution and habitat

Distributed through sub-Saharan Africa but generally absent from equatorial rainforest and desert regions. Prefers natural or artificial water bodies that have clear water with emergent and floating plants.  Its main means of obtaining food is through diving for aquatic plant seeds from the muddy bottom and it does so in waters ranging in depth from 30-180 cm. 

Distribution of White-backed duck in southern Africa, based on statistical smoothing of the records from first SA Bird Atlas Project (© Animal Demography unit, University of Cape Town; smoothing by Birgit Erni and Francesca Little). Colours range from dark blue (most common) through to yellow (least common). See here for the latest distribution from the SABAP2.  

Predators and parasites

  • Predators
  • Parasites
    • Platyhelminthes (flatworms) > Trematoda (flukes)
      • Trichobilharzia schoutedeni (recorded from Rwanda)
  • Pathogens
    • Mycobacterium causing avian tuberculosis (recorded in captivity)

Food

  • Seeds of aquatic plants (about 97% of diet)
    • Nymphaea nouchali (Blue water lily)
    • Nymphoides indica (Small yellow water lily)
    • Persecaria limbata (Knotweed)
    • Echinochloa stagnina (Long-awned water grass)
    • Paspalidium geminatum (Swamp grass)
    • Aeschynomene nodulosa (Knuckle-bean)
    • Polygonum
  • Vegetative parts of aquatic plants (about 3% of diet)
    • Nymphaea nouchali (Blue water lily)
  • Animal matter (small percentage of diet)
    • Diptera (flies) > Chironomidae (midge) larvae.

Breeding

  • Nest is built by both sexes and is located in a dense stand of reeds or rushes or grasses or sedges growing in the water. The vegetation is bent over to form a vegetative base to the nest, with some of the bases of the bent over stems forming a wall round the nest, broken in one part by an access ramp leading to the water. The nest can be floating or built up on the vegetation to as high as 45 cm above water level. It is sometimes built on top of an old grebe or Red-knobbed coot nest. There is also vegetation overhanging the nest, which helps to obscure it from above. The nest itself consists of a bowl of dead or living plant material drawn in from around the site and padded with green aquatic grass.
 

White-faced duck nest with eggs, Wakkerstroom, South Africa. [photo Warwick Tarboton ©]

 
  • Breeding season is year-round.
  • The female lays a clutch of 4-9 eggs at a rate of one per day (up to 11 eggs have been recorded in a clutch but this is though to be due to egg dumping by other females). After the clutch has been completed, both sexes incubate the eggs for 29-33 days before they hatch. The female incubates at night and for about an hour in the middle of the day, and the male incubates for the remainder of the day. Nest changeover is communicated through an exchange of calls and a bird usually approaches the nest underwater. 
  • Ducklings are able to swim, dive and feed within 20 hours of hatching. They are 50% of adult size by 27 days old; by 34 days they have all their feathers except for some wing feathers, and by 55 days they look exactly like the adult. The adults accompany the brood until at least fully grown and are highly protective of them, using the 'broken wing act' to draw predators away from the ducklings, the latter of which scatter and hide when danger lurks. 

Threats

Not considered under threat. However, noteworthy that White-backed ducks disappeared from certain water bodies after the introduction of Tilapia fishes, caused by the fishes destroying most of the aquatic vegetation. 

Links

References

  • Hockey PAR, Dean WRJ and Ryan PG (eds) 2005. Roberts - Birds of southern Africa, VIIth ed. The Trustees of the John Voelcker Bird Book Fund, Cape Town. 

 
 

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