ANSERES THALASSOKNIS 151 



Length 17'0 ; wing 7'75 ; tail 2-0; tarsus 1-25; culmen_ 1/75. 

 The sexes are alike ; young birds are less ochraceous and more 

 brown on the abdomen. 



Distribution. The White-backed Duck is confined to Africa 

 and Madagascar. It ranges from Abyssinia on the east and from 

 Loango on the west, southwards through East Africa and Nyasaland 

 to Cape Colony. 



Within our limits it is widely spread where suitable conditions 

 exist but it has not yet been met with in Khodesia or on the 

 Zambesi, though probably to be found there. The following are 

 localities : Cape Colony Verloren Vlei iu Piquetberg, (Smith, 

 type), Cape division (S. A. Mus.), Simonstown (Novara), Port 



" FIG. 45.^-Head of TJialassomis leuconota. x \ 



Elizabeth, rare (Brown), Vaalpens Pan near Mafeking (Nicolls and 

 Eglington) ; Natal Clairmont near Durban, breeding November to 

 February (Millar), Newcastle district, September to October, breed- 

 ing (Butler and Feilden) ; Orange River Colony Kroonstad, March 

 (Symonds) ; Transvaal Potchefstroom rare (Ayres), Pienaars 

 River Bridge iu Pretoria district, April (Pentber), Modderfontein, 

 breeding, April (Haagner) ; Bechuanaland Tebra county, February 

 (S. A. Mus.), Nocana, July (Fleck), Botletli River (Bryden) ; 

 German South-west Africa generally scarce, but common at Oman- 

 bondeand Ondonga (Andersson). 



Habits. This Duck is found on lagoons and about the mouths of 

 rivers and also inland on the larger pans and rivers, as a rule singly 

 or in pairs. It seldom flies, but nearly always dives into shelter 

 when disturbed. Most observers say that it has almost lost the 

 power of flight and is only able to skim along the surface of the 

 water, but Ayres states that it rises easily and flies well. The flesh 

 is very oily and unpalatable, 



