ISOLATION OF THE MALE 63 



in the life of the Black Grouse, a bird which has 

 always excited the curiosity of naturalists on 

 account of the special meeting places to which 

 both sexes resort in the spring. Mr Edmund 

 Selous watched these birds in Scandinavia, 

 where he kept a daily record at one of the 

 meeting places. In various passages he refers 

 to the appropriation of particular positions by 

 particular males, and concludes thus : " It would 

 seem from this that, like the RufFs, each male 

 Blackcock has its particular domain on the 

 assembly ground, though the size of this is in 

 proportion to the much greater space of the 

 whole. On the other mornings, too, the same 

 birds, as I now make no doubt they are, 

 have flown down into approximately the same 

 areas." 



The cliff-breeding species — Guillemots, Razor- 

 bills, and Puffins^ — are difficult to investigate 

 because individuals vary so little, and the sexes 

 resemble one another so closely ; yet, despite 

 these difficulties, we can gain some idea of the 

 general purport of their activities. But when 

 the ledges are crowded and the air is filled with 

 countless multitudes, how is it possible to keep 

 a single bird in view for a sufficient length of 

 time to understand its routine ? The difficulty 

 is not an insuperable one. The flights, under- 

 taken seemingly for no particular purpose, are 

 often of short duration and are completed before 

 the strain of observation becomes too great ; 

 moreover an individual sometimes possesses a 

 special mark or characteristic which serves to 



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