INTRODUCTION xiii 



from the material so obtained valuable, and in many cases new information was 

 gained. An interesting collection of over six hundred Grouse skins has been 

 prepared, showing the types of plumage found in both sexes at different times 

 of the year and in different districts, and also certain abnormalities. Selections 

 from this collection and from the other material collected by the Committee 

 were exhibited at a soiree of the Royal Society irTMay 1909, and at the Vienna 

 Sports Exhibition of 1910. 



The Committee began their observations in the field in the autumn of 1905 ; 

 during this season and 1906 the stock of Grouse both in Scotland and England 

 was remarkably healthy, and an excellent opportunity was thus given to study the 

 bird under normal conditions. The Field Observer visited many moors, his visits 

 extending over a period of seven months, from April to October. During this 

 time he got into close touch with the Committee's correspondents in different 

 parts of the country, checked their information, and with their assistance studied 

 the varying conditions governing particular districts. Whenever a case of 

 suspected " Grouse Disease " was reported the moor was visited by the Field 

 Observer or one of his assistants, and specimens of suspicious birds were subjected 

 to laboratory examination. 



During 1907 a considerable mortality amongst the Grouse in certain districts 

 was reported in the spring and early summer months. The Committee's experts 

 made a very careful investigation into every case reported, but, contrary to 

 expectation, it was not found that the character of the disease differed materially 

 in its essential features from those occasional isolated cases of mortality which had 

 occurred in the previous year. The Committee found no examples of the acute or 

 sudden form of disease which had been described by former observers. The out- 

 break of mortality, however, gave an excellent opportunity for collecting data 

 regarding the lingering or pining form of disease which has since been traced to 

 the ravages of the threadworm Trichostrongylus pergracilis? 



By 1908 the Committee had completed the preliminary work required to enable 

 the subject to be developed on scientific lines. Evidence and statistics had been 

 collected which indicated the special directions in which further investigations were 

 necessary or likely to be helpful. The natural history of the normal healthy Grouse 

 had been fully studied, and the general pathological characteristics of " Grouse 



1 In the following chapters this worm is usually called Trichostrongylus pergracilis, but some writers have 

 preserved Strongylus i>ircjracilis, it is also at times called the Strongyle or the Strongyle worm. A synonym 

 and a list of allied species are given by Dr Shipley on pp. 207 et seq. 



