158 Report S.A.A. Advan'cemext of Science. 



according to climatic conditions and the supply of food ; but it is shown 

 that the continuous practice of the eight-month system in time results 

 in the deterioration of the feather, whereas this does not follow from 

 the j'early system. The nutritive condition of the bird at the time of 

 quilling has a great intiuence upon the i]uality of the next crop of 

 feathers, and where possible the bird should be <|uilled only when in a 

 highly noui'ished state. 



The Natural Time for Quillix*;. 



To a certain (Jegree the feathers of a bird bear a relation to its 

 sexual condition. Among all birds it is found that the plumage is at 

 its highest degree of development at the commencement of the mating 

 season. The feathers of gaudily coloured bin Is are most perfect at this 

 time, and moulting in nature takes place at such a period as will enable 

 the new feathers to reach their highest perfection with the advent of 

 the mating season. The mating season for the ostrich in most districts 

 of Cape Colony commences in the months of April, May and June. If, 

 therefore, the time for quilling can be so arranged that the new crop of 

 feathers will come to ripeness during these mating months, the farmer 

 can reasonably expect that the plumes will be the best the bird can 

 produce. 



•Special Object of Investigations. 



The author's investigations were undertaken with the special 

 object of determining the cause of and remedy for the defects in 

 ostrich feathers technically known as " bars."' These are imperfections 

 in the formatio)i of the feather across any part of its length, and 

 observation shows they are due to a lack of proper separation of the 

 parts making up a feather. Bars vary greatly in number in different 

 plumes, and though sometimes scarcely noticeable, are at other times 

 so pronounced as to constitute a very serious defect in the feather. 

 Where at all conspicuous their presence results in a great depreciation 

 in the value of the plum(\ Indeed, it has been estimated that in 

 South Africa the annual losses to the farmer from the occurrence of 

 these bars may amount to as much as ^£25,000. 



Cause of the BARKiNf.. 



When the investigations were first undertaken numerous expla- 

 nations were prevalent as to the cause of the bars. Almost every 

 ostrich farmer had his pet theory, but scarcely two were found to 

 agree. A few preliminary experiments were sufficient to show the 

 fallacy of many of the current theories, and no one now believes that 

 the parasit(!s of the bird ai-e the direct cause of the defects, nor yet the 

 practice of (juilling, tiie preening of the feathers, nor even in-breeding« 

 It has l)(;en shown that similar barring defects may occin* in the feathers 

 of all birds, and this fact alone would lead one to suspect the cause to 

 be a very general one, something inherent in the actual formation of 

 all feathers, not a process peculiai" to the ostrich. 



