30 RUDOLF SÖDERBERG, STUDIES OF THE BIRDS IN NORTH WEST AUSTRALIA. 
which, as may be seen, are a bewildering imitation of the leaves of the tree that 
harbours the nest, are not withered Banksia leaves but chips of bark from another 
species of tree. But they are of the same shape and size as the former. The nest 
resembles in a bewildering manner a withered and fallen twig with leaves on it, situated 
in a fork. For the sake of comparison I may here show a picture of a nest of 
Melithreptus gularis (see fig. 16), where a disguise of a less intentional kind had been 
produced by the perfect choice of site for it. It may be thought that the origin of 
the former protective dress was due to an arrangement, reminding of this one. 
Another group of nests, also situated on thicker trunks or branches and well 
concealed, not so much by »ornamentation», but in consequence of their plate-like 
and diminutive size, comprise the nests of the type that characterizes Micrceca assi- 
miles and also Lalage tricolor. "The nest of the former is a very low wreath, fixed 
on the branch of the tree by fibres, materials of bark and similar things. Because 
of its low walls the nest coalesces with the base and is very difficult to discover in 
spite of its open situation. A nest of the latter type that I found in Mowla Downs 
also resembled a plate in form, and was lying exposed on a thick branch up in the tree. 
The walls consisted of a very scanty thin material made of fine twigs, fixed to a 
branch by mass of spiders web. The eggs were three, and in this case one might 
. perhaps speak of the appropriate colour of the eggs, 
belonging to small birds that build their nests in the 
trees. They had, as a matter of fact, large green 
and brown spots, very suitable for concealment and 
protection in this exposed position. The height of 
the nest was only sufficient great for the eggs to be 
on a level with its edge. (See fig. 17 and 18.) 
Finally I got to know another type of nest, 
whose origin has been the subject of investigation 
and explanation, viz. the swallows which build in 
cliffs. Petrochelidon nigricans neglecta commonly bred 
in the cave-like hollows that existed in the ruined 
mountain-cliffs in Mowla Downs. 
Here their nests were situated in colonies, 
gathered thickly together like those of gigantic hy- 
menopteras (see fig. 19). 
What I wish especially to keep in view is the 
different development of the nests in the same colony 
with regard to the form of the entrance and appearance. 
Not all the nests possessed the tubeformed projection 
that characterizes a further development of the com- 
mon nest-type with entrance-hole in the form of a 
slit. Some nests, which were inhabited, had the latter 
Fig. 16. Nest of Melithreptus gularis (drawing and simpler form, but these were perhaps to be 
Mr på Rad, 0 Museum completed with a tube. One could accordingly see 
