BRITISH BIRDS. 95 



to the one mimicked. Now, June 17, 1874, I saw a cock Blackbird in full 

 pursuit of a Cuckoo. They passed close to my face, the Cuckoo being much 

 alarmed. The resemblance here did not avail the Cuckoo as any defence, 

 on the contrary. If a person goes out hunting he puts on a red coat ; but 

 another about to commit a burglary would hardly clothe himself in so con- 

 spicuous a garment. The Cuckoo breaks into, so to speak, the nests of other 

 birds, who, if they saw a Hawk, would invariably direct their attention to it 

 at once ; whereas concealment is necessary to the operations of the Cuckoo, 

 and the less its plumage creates observation the better. Theory on these 

 subjects is always dangerous ; nevertheless to both Hawk and Cuckoo the 

 plumage may tend to safety in a resemblance to the bark of trees. 



Mr. Proctor, quoting Voltaire, in 'The Orbs around us,' observes that 

 " theory is like a mouse which passes through nineteen holes and is stopped 

 at the twentieth." I should not wonder if, instead of the Cuckoo being a 

 mimic of a Hawk, both should be found to mimic something else. 



In the Common Heron, which perches on the top of a wood, its form 

 standing out against the light, the plumage of course matches the blue of the 

 skyscape ; and I have observed how difficult it is to discern the bird in such 

 a situation. I would not, however, say any thing against mimicry, which 

 appears to be an established fact and can be read about in Mr. Wallace's 

 ' Natural Selection,' in which moths resembling birds, dung, and mortar, and 

 Mr. Salvin's case of mimicry among Hawks, are salient examples and afford 

 room for very interesting speculation. 



Colonel Irby (' Straits of Gibraltar,' p. 36) gives the Moorish name of 

 the Sparrow-Hawk, " Bou-umeira takouk" (Cuckoo-Hawk). 



