VALUE OF BIRDS TO MAN. 



71 





trees near the shore of the Musketaquid a small flock of 

 Myrtle and Black-poll Warblers, busily feeding on a swarm 

 of plant lice. There Avere not more than fifteen birds. The 

 insects were mainly imagoes, and some of them were flying. 

 The birds were pursuing these through the air, but were also 

 seeking those that remained on the trunks and branches. I 

 watched these birds 

 for some time, noted 

 their activity, and 

 then passed on, but 

 returned and ob- 

 served their move- 

 ments quite closely 

 at intervals all day. 

 Toward night some 

 of the insects had 

 scattered to neigh- 

 boring trees, and a 

 few of the birds 

 were pursuing them 

 there ; but most of 

 the latter remained 

 at or about the place 

 Av h e r e the aphis 

 swarm Avas first seen, and they Avere still there at sundown. 

 The swarm decreased rapidly all day, until just before sunset 

 it was difiicult to find even a few specimens of the insect. 

 The birds remained until it Avas nearly dark, for they Avere 

 still finding a fcAV insects on the higher branches. The plant 

 lice I had secured for identification Avere destroyed or lib- 

 erated during the night, probably by a deer mouse which 

 frequented the camp ; so the next morning at sunrise I went 

 to the trees to look for more specimens. The birds, Iioaa'- 

 ever, AA^ere there before me, and I Avas unable to find a single 

 aphis on the trees. The last bird to linger Avas more suc- 

 cessful than I, for it Avas still findins^ a fcAv : but it soon grave 

 up the eftbrt, and left for more fruitful fields. Probably a 

 fcAv insects escaped by flight ; Init in examining the locality 

 in 1905 I could not find one. The apparently complete 



Figr. 29. — Warblers destroying a swarm of plant lice. 



