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 acommon one in the genus. The result is, 
that on a superficial examination the birds are identical, 
although they have important structural differences, 
