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 Yireos 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. 



