Expedition to the White Nile. 275 



119. '^Plectroptbrus rueppelli Sclat. 



Spur-winged Geese were met with in fair numbers all 

 along the river. They were still more shy than the Egyptian 

 Geese, and were very difficult to shoot. We never saw a 

 large flock, and often two or three were in company with 

 a flock of Ghenalopex agyptiaca. 



120. *Dafila acuta (Linn,). 



A small flock seen near Duem on March 26th. 



121. *Dendrocycna viDUATA (Liuu.). 



We did not notice this Duck until towards the end of April. 

 From Shebesha, where we arrived on our way down the 

 river on April 23rd, to Khartum it was common in small 

 flocks at the edge of the river. It is very good for food. 



122. Pteroclurus exustus (Temm.). 



Mr. Hartert has separated (Nov. Zool. vol. vii. p. 28, 

 March 1900) the true North-eastern and Central African 

 P. exustus, which is always strongly marked with dark 

 olive-brown on the back, from the Somaliland bird, which, 

 besides being smaller, is of a pale sandy colour on the back. 

 This form Mr. Hartert calls Pterocles exustus somalicus, 

 and my bird from the White Nile exactly agrees with it. 

 Thus the Sand-Grouse of the portion of the White Nile 

 district extending from Khartum to 160 miles south, instead 

 of agreeing with the birds to the north and to the south 

 of it, is of the same form as is to be found far to the 

 eastward. 



These Sand-Grouse were met with everywhere in astonish- 

 ing numbers. Their flights from the desert to the river each 

 morning at certain spots were exceedingly regular. So large 

 were the flocks in certain places, that the incessant stream of 

 small parties rushing down to the water lasted for over an 

 hour. On several broad grassy flats near the river a large 

 number of Sand-Grouse were to be found all day, and they 

 seemed to live and feed there in preference to the arid tracts. 

 But at these spots there were always other individuals, which 

 came down from the desert in the usual way to drink in the 

 morning, and flew back again at once, and others again which 



t2 



