THE BIRDS OF SlNrxAPORE ISLAND 
We have no space here to deal with the structure of a 
feather, but it may be mentioned that the sijght stickiness or 
reluctance with which the web of a feather is split or parted 
with the fingers is due to an iiiterlockitiK arrangemennt of 
many thousands of tiny liook-Hke structures, examination of 
which is open to all by placing a piece of feather under a 
raiscroscope. 
To conclude our notice of feathers we must mention the 
important and usually unsuspected fact that, norgially, feathers 
only grow on well defined arid comparatively narrow "feather 
tracts" the intervening spaces often being quite bare. The 
feathers are of course long enough to cover these bare spaces. 
H all the feathers on a dead bird are clipped off close to 
the skin with a pair of scissors this arrangement of feather- 
tracts will be admirably demonstrated and it will then be seen 
that the feathers only grow on narrow tracts {pterylte) that 
may be likened to the paths that encompass and cross a garden, 
the lawns representing the un feathered space {aptcrmj. The 
feathers wear out and to a certain extent fade and are renewed 
at least once a year the process being known as "moulting": 
the moult is a much more complicated affair than it appears 
to be and we know little of the way in which it is carried out 
in Malayan birds* 
The feathers together constitute the plumage and it is with 
the characters, chieriy the colouring, of this plumage combined 
with the external form of the bird and certain external measure- 
ments that systematic oniithoiogy is at the moment most 
largely concerned. 
In some birds the young and old of both sexes wear a 
similar plumage throughout the year: in others the male and 
female each have a distinctive dress, tlie young birds of both 
sexes resembling the female until their first moult when the 
males assume the adult livery of their sex. In yet other birds 
a distinct and often resplendent breeding plumage is acquired 
and worn only a few months when it is cast off and replaced 
by the duller, "winter" (non-breeding) plumage and to these 
three conditions we could add yet others. 
[>8] 
