SUPPLEMENTAL FEATHERS. 95 



for swift motion. The emu is not so swift footed as 

 the ostrich, and the feathers upon it are all more 

 nearly of the same length and form. Judging from its 

 structure, for of its habits we know nothing, the apte- 

 ryx is but a slow moving bird, and the feathers upon 

 it are all pendent and flexible, resembling thatch as 

 much as they do ordinary feathers. 



The supplemental or ornamental feathers, of 

 which the uses are not well known, appear on 

 various parts of the body. They are generally 

 confined to the male birds, or at least most conspicu- 

 ous in them ; and in some instances, as in that of the 

 ruif, they make their appearance only during the 

 breeding season. Birds which are subject to addi- 

 tional plumage, or even to rich additional colours in 

 their feathers, during the breeding season, are gene- 

 rally, if not invariably, birds of warm temperament, 

 and excited to contests of gallantry with each other, 

 and other displays of more than ordinary courage, at 

 that season. The affection appears to be one of 

 the whole body, though the effects which it produces 

 are differently localised in different species. Some- 

 times the additional feathers are on the neck, some- 

 times in the crest, sometimes in the scapulars and 

 feathers of the back, and very generally in the tail. 



The use of these feathers in the economy of the 

 birds is not known ; unless it be that the production 

 of them (for feathers appear to be one of the most 

 elaborate of nature's productions) exhausts the sur- 

 plus of that energy which, from its very violence, 

 might otherwise be injurious to them at those times 

 when they do not require to exert it immediately for 

 those purposes which, physiologically considered, it 

 is intended to answer. 



This is an exceedingly curious part of nature ; but 



