BIRDS AND NATURE 
11 
multiform, this multiformity accounting for the variety in the 
manner of flight. This latter in some cases means merely a 
change of abode, e. g. in those of partridges and quails; 
in others it is an essential preliminary to the acquisition of 
food, e. g. in that of the swallow, which seizes its flying 
prey, the insects, while in full flight. There are a whole 
series of modifications between these two extremes of wing- 
structure; we find birds which move only in a limited area, 
their sphere of influence being equally limited; and we find 
others, which migrate, according to the season, from one 
zone to the other, thus exercising an influence successively 
and in regular order on districts far apart from one another, 
with far different climates, and bringing about the trans- 
mission of bird- labour adapted to the succession of natural 
phenomena. 
The variety of flight due to the various wing-structures 
creates a system of movement which enables birds to keep 
in touch, as it were, with those phenomena of nature which 
are indispensable to their subsistence and this system implies 
the work and the effect of the same. 
The structure and effect of the wing, in its relation to birds, 
finds a parallel in that of the beak, this organ of birds so 
wonderful in its variety. If we look at the long lists of birds, 
we are met with a variety of beaks that seem to resemble a 
collection of tools; even if we merely consider the phenomena 
of our own climate, or the palaearctic zone. 
Let us take as extremes the tiny beak of the little long- 
tailed titmouse, which is smaller than a grain of rice, and 
that of the spoonbill, which is large and spoonshaped : 
between these two extremes we have the greatest variety of 
iorms and modifications, which may be characterised as 
follows: the bill of the chiff-chaff is almost as fine as a 
needle and is suitable for seizing the smallest and most 
