Manchester Memoirs, Vol. lix. ( 191 5), No. t. 3 



In 1906 an instance of a blackbird fighting its reflec- 

 tion in a cellar window of a house in Knutsford, Cheshire, 

 came under my notice. In this case the bird behaved 

 rather differently from mine and Mr. Moffat's ; it did not 

 fly against the window, but slipped between the bars 

 which guarded it and, standing on the sill, battled with its 

 reflection. 



This " sphere of influence," well known to ornitholo- 

 gists, is usually only dominated by the male bird during 

 the period of sexual excitement, commonly termed, the 

 breeding season. The male bird in most species defends 

 the immediate neighbourhood of his mate's nest against 

 any possible rival for her affections. The area of the 

 sphere varies according to the sociability of the species 

 and to the pugnacity of the individual. In the case of 

 species which are gregarious during the breeding season — 

 the rook for example — the nest and its contents alone are 

 defended, but in solitary species, such as the mistle 

 thrush, the area is much greater. The mistle thrush will 

 not only attack and drive away others of its kind, but it 

 will assault any bird or mammal, including man, which 

 approaches the nest ; presumably the mistle thrush 

 imagines that any intruder on its domain may have 

 sinister designs. 



The blackbird, so far as I have observed, confines its 

 attention mainly to rival cock blackbirds, but it will mob 

 with threatening cries any cat, owl or other predatory 

 creature that may approach. The sphere of influence of 

 the particular blackbird under consideration was evidently 

 mapped out by the bird before the nest was built, and 

 even before there was evidence that a mate had been 

 selected and secured. 



That a bird filled with the martial spirit of spring 

 rivalry should imagine that its own reflection in a mirror 



