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Degeneration m the Ostrich 



having no oil or preen gland the loose feathers absorb and retain water 

 instead of allowing it to run off as in the familiar duck. An ostrich 

 exposed to rain presents a bedraggled and sorry spectacle, its plumage 

 clinging to its body like a veritable " wet blanket." The effects of 

 exposure are mainly felt at low levels, subject to continued, cold coastal 

 rains : at high elevations rains are infrequent, and are mostly short, 

 sharp, thunder showers with rapid return of sunshine. A more complete 

 covering would therefore be no remedy against the former conditions, 

 but rather the reverse. The oiling of the feathers from a preen gland 

 would alone suffice, and also prevent the high depreciation in the feather 

 crop consequent upon its becoming wet and muddy, as well as that of 

 the graceful millinery plume when exposed to humid weather. 



At first no close connection would appear to exist between two such 

 widely distinct phenomena as the geographical distribution of the ostrich 

 and the absence of a simple structure like an oil gland. Yet from the 

 above considerations it is manifest that the inability to oil its loose 

 feathers limits the bird to an arid climate, and also restricts successful 

 ostrich farming to the same conditions, as many a farmer^ has found to 

 his sorrow in attempting to introduce the bird to humid areas. Under 

 the circumstances, it will readily be admitted that the extensive plumage 

 losses which have already occurred have little or no adaptive significance, 

 and therefore little or no selection value; climatic conditions vastly 

 outweigh in importance any loss of plumage hitherto, and particularly 

 the slight variations between one individual and another. 



As regards the small size of the wings, no longer of use for flight, the 

 welfare of the bird would suffer to a certain degree by their continued 

 reduction, though probably no disadvantage has occurred hitherto. They 

 are of much assistance in steering the bird in its erratic movements, par- 

 ticularly when twisting and turning, and also in its courageous but none 

 too graceful waltzing display. When raised and lowered, either together 

 or alternately, the wings enable the bird to perform rapid turning move- 

 ments with remarkable agility, actions which may be deemed to be of 

 some significance in escaping from the measured spring of the larger 

 carnivora. The wings are also necessary in the frequent practice of 

 taking a " sand bath," when they throw the dry sand and dust over the 

 body of the bird, a doubtful remedy against skin and feather parasites. 

 During natural incubation they are essential for covering the large nest 

 of eggs. On the whole, however, we may hold that the wing reduction 

 hitherto has had no harmful result, but should it continue a stage will 

 be reached when it will have a negative selection value. 



