142 BIRDS OF DAMARA LAND. 



where they restlessly hop from branch to branch on the 

 bushes and the lower boughs of the trees, never re- 

 maining long on the same tree, but hunting most syste- 

 matically for insects, which, with the occasional addition 

 of young shoots and leaves, form their food. Whilst 

 some individuals of the nock are examining a tree in 

 search of insects, others keep moving slowly on, but 

 rarely going further than the next tree. When the 

 locality is open, those which first reach a tree fix their 

 gaze intently on the ground, and, if any prey be in sight, 

 pounce upon it with great celerity, their companions, 

 whilst the successful foragers are devouring their booty, 

 continuing to move on slowly as before. 



The irides in this species are of a bright lemon-colour, 

 the fringe round the eyes orange, the bill black, and the 

 legs flesh-coloured. 



Measurements of a male : 



in. lin. 



Entire length 80 



Length of folded wing 43 



tarsus 11 



middle toe 06 



tail , 3 7 



", bill 10 



[Mr. Chapman, in his ' Travels in South Africa/ vol. ii. pp. 

 211, 370, calls this species the " Quagga dzerra," and speaks of 

 its '' ' riding on the withers " of the Quagga ; he also states that 

 it "has a soft, sweet, and pleasant note/' ED.] 



179. Prionops Eetzii, Wahl. Eetz's Helmet-Shrike. 



Prionops Retzii, Wahlberg, Ofvers. 1856, p. 174. 



Wahlberg, in Journal fiir Orn. 1857, p. 1. 



Gurney, Birds Damar., Proc. Zool. Soc. 1864, p. 3. 



