1 ANIMAL LIFE IN THE TROPICAL FORESTS 299 
sound very like the puff of a locomotive, and which can some- 
times be heard a mile off. They mostly feed on fruits; and 
as their very short legs render them even less active than the 
toucans, the same explanation may be given of the large size 
of their bills, although it will not account for the curious 
horns and processes from which they derive their distinctive 
name. The largest hornbills are more than four feet long, 
and their laboured noisy flight and huge bills, as well as their 
habit of perching on the top of bare or isolated trees, render 
them very conspicuous objects. 
The Picariz comprise many other interesting families— 
as, for example, the puff-birds, the todies, and the humming- 
birds ; but as these are all confined to America we can hardly 
claim them as characteristic of the tropics generally. Others, 
though very abundant in the tropics, like the kingfishers and 
the goatsuckers, are too well known in temperate lands to 
allow of their being considered as specially characteristic of 
the equatorial zone. We will therefore pass on to consider 
what are the more general characteristics of the tropical as 
compared with the temperate bird-fauna, especially as exem- 
plified among the true perchers or Passeres, which constitute 
about three-fourths of all terrestrial birds. 
Passeres 
This great order comprises all our most familiar birds, 
such as the thrushes, warblers, tits, shrikes, fiycatchers, 
starlings, crows, wagtails, larks, and finches. ‘These families 
are all more or less abundant in the tropics; but there are 
a number of other families which are almost or quite peculiar 
to tropical lands and give a special character to their bird- 
life. All the peculiarly tropical families are, however, con- 
fined to some definite portion of the tropics, a number of 
them being American only, others Australian, while others 
again are common to all the warm countries of the Old 
World ; and it is a curious fact that there is no single family of 
this great order of birds that is common to all tropical regions 
and confined to them, or that is even especially characteristic 
of the tropical zone, like the cuckoos among the Picarie. 
The tropical families of passerine birds being very numerous, 
and their peculiarities not easily understood by any but orni- 
