296 TROPICAL NATURE ur 
curious interactions of animals on each other, by which their 
distribution, their habits, and even their colours, may have 
been influenced, for the most conspicuous pigeons, whether by 
colour or by their crests, are all found in countries where 
they have the fewest enemies. 
Picarice 
The extensive and heterogeneous series of bird till recently 
comprised under this term includes most of the fissirostral 
and scansorial groups of the older naturalists. They may be 
described as, for the most part, arboreal birds, of a low grade 
of organisation, with weak or abnormally developed feet, and 
usually less active than the true Passeres or perching birds of 
which our warblers, finches, and crows may be taken as the 
types. The order Picarie comprises twenty-five families, some 
of which are very extensive. All are either wholly or mainly 
tropical, only two of the families—the woodpeckers and the 
kingfishers—having a few representatives which are per- 
manent residents in the temperate regions, while our summer 
visitor, the cuckoo, is the sole example in Northern Europe 
of one of the most abundant and widespread tropical families 
of birds. Only four of the families have a general distribu- 
tion over all the warmer countries of the globe—the cuckoos, 
the kingfishers, the swifts, and the goatsuckers; while two 
others—the trogons and the woodpeckers—are only wanting 
in the Australian region, ceasing suddenly at Borneo and 
Celebes respectively. 
Cuckoos 
Whether we consider their wide range, their abundance in 
genera and species, or the peculiarities of their organisation, 
the cuckoos may be taken as the most typical examples of this 
extensive order of birds; and there is perhaps no part of the 
tropics where they do not form a prominent feature in the 
ornithology of the country. Their chief food consists of soft 
insects, such as caterpillars, grasshoppers, and the defenceless 
stick- and leaf-insects ; and in search after these they frequent 
the bushes and lower parts of the forest, and the more open 
tree-clad plains. They vary greatly in size and appearance, 
from the small and beautifully metallic golden-cuckoos of 
