104 MIMICRY, AND OTHER PROTECTIVE 



and very pugnacious, frequently driving away crows, 

 and even hawks, which perch on a tree where a few of 

 them are assembled. They are all of rather dull and 

 obscure colours. Now in the same countries there is 

 a group of orioles, forming the genus Mimeta, much 

 weaker birds, which have lost the gay colouring of 

 their allies the golden orioles, being usually olive-green 

 or brown ; and in several cases these most curiously 

 resemble the Tropidorhynchus of the same island. For 

 example, in the island of Bouru is found the Tropido- 

 rhynchus bouruensis, of a dull earthy colour, and the 

 Mimeta bouruensis, which resembles it in the follow- 

 ing particulars : The upper and under surfaces of the 

 two birds are exactly of the same tints of dark and 

 light brown ; the Tropidorhynchus has a large bare 

 black patch round the eyes; this is copied in the 

 Mimeta by a patch of black feathers. The top of the 

 head of the Tropidorhynchus has a scaly appearance 

 from the narrow scale-formed feathers, which are imi- 

 tated by the broader feathers of the Mimeta having a 

 dusky line down each. The Tropidorhynchus has a 

 pale ruff formed of curious recurved feathers on the 

 nape (which has given the whole genus the name of 

 Friar birds) ; this is represented in the Mimeta by a 

 pale band in the same position. Lastly, the bill of the 

 Tropidorhynchus is raised into a protuberant keel at the 

 base, and the Mimeta has the same character, although 

 it is not a common one in the genus. The result is, 

 that on a superficial examination the birds are identical, 

 although they have important structural differences, 



