vi A THEORY OF BIRDS' NESTS 133 



Real or apparent Exceptions to the Law stated at page 124 



The only marked exceptions I have been able to discover 

 are the following 



1. King crows (Dicrourus). These birds are of a glossy 

 black colour, with long forked tails. The sexes present no 

 difference, and they build open nests. This apparent excep- 

 tion may probably be accounted for by the fact that these 

 birds do not need the protection of a less conspicuous colour. 

 They are very pugnacious, and often attack and drive away 

 crows, hawks, and kites ; and as they are semi-gregarious in 

 their habits, the females are not likely to be attacked while 

 incubating. 



2. Orioles (Oriolidse). The true orioles are very gay birds ; 

 the sexes are, in many Eastern species, either nearly or quite 

 alike, and the nests are open. This is one of the most serious 

 exceptions, but it is one that to some extent proves the rule ; 

 for in this case it has been noticed that the parent birds 

 display excessive care and solicitude in concealing the nest 

 among thick foliage, and in protecting their offspring by in- 

 cessant and anxious watching. This indicates that the want 

 of protection consequent on the bright colour of the female 

 makes itself felt, and is obviated by an increased development 

 of the mental faculties. 



3. Ground thrushes (Pittidse). These elegant and brilliantly- 

 coloured birds are generally alike in both sexes, and build an 

 open nest. It is curious, however, that this is only an ap- 

 parent exception, for almost all the bright colours are on the 

 under surface, the back being usually olive-green or brown, 

 and the head black, with brown or whitish stripes, all which 

 colours would harmonise with the foliage, sticks, and roots 

 which surround the nest, built on or near the ground, and 

 thus serve as a protection to the female bird. 



4. Grallina Australis. This Australian bird is of strongly 

 contrasted black and white colours. The sexes are exactly 

 alike, and it builds an open clay nest in an exposed situation 

 on a tree. This appears to be a most striking exception, but 

 I am by no means sure that it is so. We require to know 

 what tree it usually builds on, the colour of the bark or of 

 the lichens that grow upon it, the tints of the ground, or of 



