2 THE STRUCTURE AND LIFE OF BIRDS cCuapP. 
their grace and sprightliness. Not even the most 
dazzling and ethereal of Humming-birds surpasses 
the Wheatear in beauty. High spirits are another 
sign of vitality in most if not in all birds. The Thrush 
will sing by the hour together for pure jollity. With 
our English birds this is the common way of giving 
expression to hilarity. Some foreign species hold 
most elaborate dances, and in all lands the fights 
among the cock birds in spring are signs of exuber- 
ant life. To find food and meet the actual needs 
of the day seems easy enough, so that there is a 
large surplus of energy to devote to pleasure or 
rivalry. 
There is nothing in nature more wonderful than the 
instincts of birds—for the present we must use this 
much-debated word without explanation—nothing, 
perhaps, that presents more interesting problems. 
Take, for instance, the migratory instinct. The 
Swallow travels to the south of Africa to spend the 
winter and returns in spring to build her nest, often 
in the very chimney where she reared her brood the 
previous year. 
The nests are in many ways interesting, from their 
beauty, from their wonderful variety—birds belonging 
to the same family often building quite differently—and 
from the fact that young birds have to build their first 
nest without any instruction. Take again the extra- 
ordinary instinct of the Cuckoo, and the still more 
extraordinary instinct of her infant progeny. Then, 
too, there is the death-feigning and wound-feigning 
instinct. All these, however much they may be 
studied, can never lose their interest 
