IX WARNING COLORATION AND MIMICRY 263 



poisonous snake which belongs also to the ElapidiB. This 

 is, no doubt, a warning to its foes, not an attempt to 

 terrify its prey ; and the hood has been acquired, as in the 

 case of the rattlesnake, because, protective coloration being 

 on the whole useful, some mark Avas required to distinguish 

 it from other protectively coloiu-ed, but harmless, snakes. 

 Both these species feed on active creatures capable of escaping 

 if their enemy were visible at a moderate distance. 



Mimicry among Birds. 



The varied forms and haljits of birds do not favour the 

 l^roduction among them of the phenomena of warning coloiu-s 

 or of mimicry ; and the extreme development of their instincts 

 and reasoning powers, as Avell as their activity and their 

 power of flight, usually afford them other means of evading 

 their enemies. Yet there are a few imperfect, and one or 

 two very perfect cases of true mimicry to be found among 

 them. The less perfect examples are those presented by 

 several species of cuckoos, an exceedingly weak and de- 

 fenceless group of birds. Ovu- own cuckoo is, in colom- and 

 markings, very like a sparrow-hawk. In the East, several 

 of the small black cuckoos closely resemble the aggressive 

 drongo- shrikes of the same country, and the small metallic 

 cuckoos are like ' glossy starlings ; while a large ground- 

 cuckoo of Borneo (Carpococcyx radiatus) resembles one of 

 the fine pheasants (Euplocamus) of the same country, both in 

 form and in its rich metallic colours. 



More perfect cases of mimicry occur between some of the 

 dull-coloured orioles in the Malay Archipelago and a genus of 

 large honey-suckers — the Tropidorhynchi or " Friar -birds." 

 These latter are powerful and noisy birds which go in small 

 flocks. They have long, curved, and sharp beaks, and power- 

 ful grasping claws ; and they are quite able to defend them- 

 selves, often driving away crows and hawks Avhich venture to 

 approach them too nearly. The orioles, on the other hand, 

 are weak and timid birds, and trust chiefly to concealment 

 and to their retiring habits to escape persecution. In each 

 of the great islands of the Austro-Malayan region there is a 

 distinct species of Tropidorhynchus, and there is always along 

 ■with it an oriole that exactly mimics it. All the Tropidorhynchi 



