THE BIRD-LIFE OF A YEAR. 19 
conditions, and under the encouragement of a high 
temperature we may be visited by bird ‘‘ waves”’ 
which flood the woods with migrants. Birds are 
then, doubtless, more abundant than at any other 
period of the year. As many as ten species may be 
noted as arriving on the same day, while the num- 
ber of individuals observed may almost exceed cal- 
culation. At this season it is not unusual to observe 
from sixty to eighty species of birds during a few 
hours’ outing, and Mr. W. L. Dawson records that, 
with Prof. Lynds Jones of Oberlin College, he re- 
corded twelve species of water birds and ninety 
species of land birds in one day of field work in 
Lorain County, Ohio. 
After the fifteenth of the month, birds begin to 
decrease in number, the Transient Visitants passing 
further north, and by June 5 our bird-life is com- 
posed of Permanent Residents and Summer Resi- 
dents. 
It will be noticed that with few exceptions the 
birds arriving in May are insectivorous ; particularly 
those insect-eating birds which obtain their food 
from the vegetation. Thus, no sooner are the un- 
folding leaves and opening blossoms exposed to the 
attack of insects than the Warblers and Vireos ap- 
pear to protect them, and the abundance of these 
small birds is the distinctive feature of the bird-life 
of the month. 
Their diminutive size, activity, and the persistence 
with which they remain in the tree-tops render their 
identification in life by no means an easy matter, 
and more than any of the other land birds they test 
the patience of the field student. 
