25'^ SOMK RRSTLTS OF OSTRICH ] N VESTIGATTOXS. 



The secondary sexual colours of the skin and plumage of the 

 ostrich are thus determined hy altogether different influences ; the 

 full attainment of the ope is dependent upon the ])resence of 

 the testes, and of the other upon the absence of the ovaries. Two 

 North African birds at Grootfontein, although about six years 

 old, have shown no signs of sexual maturity ; they retain the cream 

 yellow of all northern young birds and mature hens, but have the 

 black plumage of cocks. Evidently some abnormality is connected 

 with the internal gonads, but from the external api)earance of 

 the birds it is impossible to say whether they are cocks or hens. 

 It may be noted that the removal of the ovaries or testes, especially 

 after a bird has attained maturity, has little or no effect on certain 

 of the sexual instincts. Thus a spayed hen will go through the 

 characteristic snap]:)ing of the beak and fluttering of the wings 

 as if broody, and will crouch to receive the cock ; while the cas- 

 trated cock will perform his ordinary " rolling" display and even 

 mount a crouching hen. 



Tluis the scarlet colour of the cock is a secondary .sexual 

 character, it may well be doubted whether it has any influence on 

 the mating of the birds, or any preferential value in the eyes of 

 the hen, as is so often sup])osed to be the case with the bright 

 nuptial Colours of birds. For northern cocks are a bright 

 scarlet over all their exposed parts at the time of sexual ripeness, 

 while southern cocks are scarlet only over the head and the tarsus, 

 and are far less striking in their general appearance, yet a northern 

 hen will crouch just as freely for the latter as for the former. 

 ( )ccasionally ostriches exhibit a dim suggestion of ])referential 

 mating, but in practice it is found that any hen will jjair with any 

 cock, and in " camjjing off " as breeders the farmer never takes 

 into account any possible preferences on the part of the birds 

 themselves. In a state of nature, on the open veld, a cock 

 gathers around him one or more hens as the breeding season 

 approaches, and very definite si)atial limitations become 

 established among the different breeding sets, and woe l^etide 

 any cock which may wander on the area appropriated by another. 

 In all this, however, the hens are purely passive and indifferent, 

 and are prone to lay in the same nest, as many as 60 or 70 eggs 

 being sometimes found in the one shallow depression. Further, 

 as in most other birds, the plumage is at its highest state of 

 development at the beginning of the mating season, as if still 

 further adding to the attractiveness of the cock. Yet farmers as 

 often as not clip the plumes before mating the birds, and so 

 preserve them froiu wear and tear, without however any influence 

 on the readiness with which pairing takes place. 



Morgan also refers to certain experiments by Goodalc, who li;is fonnd that 

 wlien the hen of ordinary breeds of fowls is spayed, she develops the full 

 male plumage, as is also proved above for the lien ostrich. Seeing that the 

 plumage of the cock ostrich is more valuable than that of the hen, the 

 results from spaying the latter have an economic bearing, and the 

 practice is followed by some farmers. 



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