6 BIRDS OF THE WORLD 



the stomachs of dead birds have been found such 

 strange objects as a china doll, a horn comb, pieces of 

 glass, and small tools. For the same reason our 

 domestic poultry swallow pebbles — in order to grind 

 their food. 



The Ostrich further differs from his relatives in that 

 both sexes share the work of incubation ; and here the 

 difference in plumage plays an important part. The 

 female, with her dull, sandy-coloured dress, sits by 

 day, so that she is practically invisible when seen 

 against the arid wastes chosen for the nesting-site. 

 The male sits by night, when his dark plumage renders 

 him invisible also. Like the Rhea, the Ostrich is 

 polygamous, and several hens lay their eggs together 

 in the same nest. See Plate 28, Fig. 157. 



Though four distinct species of Ostrich are recog- 

 nised by ornithologists, they do not differ greatly in 

 appearance one from another, except in the colour of 

 the legs, one of the South African forms having skin 

 of a reddish hue, while the species found in Somali- 

 land has dark bluish-grey thighs. These great birds 

 are often found in company with herds of antelopes 

 and zebras. 



In all the Ostrich-like birds so far described, the 

 nestlings are striped with broad bands of white and 

 black, or brown, which run from head to tail. This 

 striping is, however, not equally well marked in all 

 the species. It is most clearly seen in the young of 

 the Emu and of the Cassowary. In the young Ostrich 

 the neck is striped, but the down of the body shows 

 no stripes, these being obscured by the tips of the 



