l82 Campbell, The Family Certhiidcc in Australia. [ ,st^Aprii 



lencoptera (north-west Australia and Northern Territory), being 

 separable from each other by the latter having a white under 

 surface while the former is streaked. 



In nidification the genus Sittella is far more interesting than 

 Climacteris. The Tree-creeper builds a nest in the hole of a 

 tree, which offers little scope for architecture, but the nest of 

 the Tree-runner, placed in a dead fork of a eucalypt,* is a 

 masterpiece of ingenuity, for it assimilates perfectly with its 

 surroundings. It is placed like a filling of rubbish in an upright 

 fork of a branch, usually about 2 inches in thickness, and is 

 built of bits of lichen, smoothly finished outside with little flakes 

 of bark, glued on with mucus, to resemble natural bark. The 

 birds themselves, in fact, offer a likeness to the bark where they 

 commonly live. They are grey in colour, and the back is in 

 some species faintly striated. A great contrast in under surfaces, 

 however, may be noted between .S. cJirysoptera and 5. pile at a, 

 two species from southern and northern Victoria respectively. 

 The former has under surface similarly striated, though lighter 

 in colour than the upper surface, while the latter, probably 

 through living in a hotter locality, has a white under surface, 

 which in the stronger light reflects the bark in such a manner 

 that the under parts appear to be striated also. The eggs, too, 

 of Sittella are quite in accord with the remarkable adaptive 

 colour protection that is evident with bird and nest. They are 

 light grey-green in colour, with bold black blotches — a good 

 representation of the grey-green and black-blotched lichen of 

 which the inner part of the nest is made. Mr. F. P. Godfrey, at 

 a recent meeting of the Bird Observers' Club, when this family 

 of birds was under discussion, mentioned that he had seen a 

 breeding Sittella cJirysoptera leave its nest when approached and 

 cling on to the limb near by. The uncovered eggs might be 

 detected from some distance if they were not protectively 

 coloured. At the same meeting Mr. G. F. Hill pointed out the 

 adaptiveness of the Sittella pileata, for those nesting in the dead 

 branches of certain eucalypts which have bark in long strings, 

 instead of in flakes, used long strings of bark instead of flakes 

 for their nests. 



The genus Sittella are pre-eminent among our common birds 

 in evidencing the governing influence of environment on protec- 

 tive colouring. The colour of the bird assimilates with that of 

 the tree branches on which it lives ; the colour of the nest 

 resembles that of the branch, and therefore that of the bird as 

 well ; and the colour of the eggs imitates the colour of the nest 

 inside. Further research may yet reveal other striking fitnesses. 

 It might also be pointed out that the plumage of the male is 



* A pair of Sittella chrysoptera (perhaps young birds) built a somewhat clumsy 

 nest in a live branch of a bull oak {Casuariiia) in October, 1897, at Springvale, 

 Victoria. — A. G. C. 



