MOTACILLID^ MOTACILLA 257 



its strongly contrasted colours of jet-black and pure white. It is 

 most frequently met with on the borders of large rivers and vleis, 

 almost invariably in pairs. It is also partial to pasture land where 

 it follows the cattle and horses for the sake of the flies and other 

 insects which infest them. It feeds also on small beetles, the larvae 

 of various water insects and mosquitoes. The latter it catches 

 on the wing whilst skimming over the surface of the water. The 

 ordinary note of this Wagtail is a sharp " chirrup " resembling that 

 of the other species ; in spring and summer it has a low pitched 

 but pleasant and melodious song. It runs with great celerity, and 

 its long tail is incessantly in motion, vibrating up and down. Its 

 nest, built in September in inland districts, but about the beginning 

 of August on the coast of N atal, is placed in a hole, on a ledge of 

 rock, or against the bank of a stream. It is rather large, with 

 thick walls and is cup-shaped, constructed outwardly of dead 

 leaves, tendrils and dry grass and lined with finer grass, rootlets 

 and hair. The eggs, from three to five in number, are larger than 

 those of the Cape Wagtail, of a pale brown ground-colour, thickly 

 freckled and spotted all over with darker brown and grey. They 

 measure O90 x 0-60. 



148, Motacilla longicauda, Grey-backed Wagtail. 



Motacilla longicauda, Biipp. N. Wirb. Vog. p. 84, pi. 29, fig. 2 (1835) ; 

 Layard, B. S. Afr. p. 119 (1867) ; SJiarpe, ed. Laijard's B. S. Afr. 

 p. 544 (1884) ; id. Cat. B. M. x, p. 495 (1885) ; Shelley, B. Afr. i, 

 p. 11 (1896). 



Description. Adult male. Above, crown and upper surface of 

 body delicate blue-grey ; lesser wing-coverts blackish edged with 

 grey ; inner greater coverts white, the centre of the outer web 

 black ; remaining coverts black tipped with white ; quills black, 

 the outer primary with a patch of white towards the centre of the 

 inner web, the amount of white increasing with each succeeding 

 quill until the inner web at the base is entirely white, the outer 

 webs of the inner secondaries also broadly margined with white 

 toward the ends ; four centre tail-feathers black edged with white ; 

 rest of tail-feathers pure white ; eyebrow and eyelids white ; fore- 

 head and lores dusky ; ear-coverts grey and white ; cheeks and 

 under surface of body white interrupted by a black crescent across 

 the lower throat, the sides and flanks tinged with blue-grey ; 

 17 



