242 A THEORY OF BIRDS’ NESTS. 
neck, and are very conspicuous. The sexes are exactly 
alike, and the nest is in a hole of a tree. 
8. Toucans (Rhamphastide). These fine birds are 
coloured in the most conspicuous parts of their body, 
especially on the large bill, and on the upper and lower 
tail coverts, which are crimson, white, or yellow. The 
sexes are exactly alike, and they always build in a hol- 
low tree. 
9. Plaintain-eaters (Musophagide). Here again the 
head and bill are most brilliantly coloured in both sexes, 
and the nest is in a hole of a tree. 
10. Ground cuckoos (Centropus). These birds are 
often of conspicuous colours, and are alike in both sexes. 
They build a domed nest. 
11. Woodpeckers (Picidz). In this family the fe- 
males often differ from the males, in having a yellow 
or white, instead of a crimson crest, but are almost as 
conspicuous. They all nest in holes in trees. 
12. Parrots (Psittaci). In this great tribe, adorned 
with the most brilliant and varied colours, the rule is, 
that the sexes are precisely alike, and this is the case 
in the most gorgeous families, the lories, the cockatoos, 
and the macaws; but in some there is a sexual dif- 
ference of colour to a slight extent. All build in holes, 
mostly in trees, but sometimes in the ground, or in 
white ants’ nests. In the single case in which the nest 
is exposed, that of the Australian ground parrot, Pezo- 
porus formosus, the bird has lost the gay colouring of 
its allies, and is clothed in sombre and completely pro- 
tective tints of dusky green and black. 
