7 © Birds Every Child Should Know 
soft grayish or olive green on their backs, wings, 
and tail, whitish or yellow below. Some people 
call them greenlets. They are all a little smaller 
than sparrows. More inconspicuous birds it 
would be hard to find or more abundant, al- 
though so commonly overlooked except by 
people on the look-out for them. Where the 
new growth of foliage at the ends of the branches 
is young and tender, many insects prefer to lay 
their eggs that their babies may have the most 
dainty fare as soon as they are hatched. They 
do not reckon upon the vireos’ visits. 
Toward the end of April or the first of May, 
these tireless gleaners return to us from Central 
and South America where they have spent the 
winter, which of course you know, is no winter 
on the other side of the equator, but a con- 
tinuation of summer for them. Competition 
for food being more fierce in the tropics than 
it is here, millions of birds besides the warblers 
and vireos travel from beyond the Isthmus of 
Panama to the United States and back again 
every year in order that they may live in per- 
petual summer with an abundance of food. 
If any child thinks that birds are mere creatures 
of pleasure, who sing to pass the time away, he 
doesn’t begin to understand how hard they 
must work for a living. They cannot limit their 
labours to an eight-hour day. However, they 
keep cheerful through at least sixteen busy hours. 
