. Useful birds and their protection. Containing brief descriptions of the more common and useful species of Massachusetts, with accounts of their food habits, and a chapter on the means of attracting and protecting birds . were pursuing themthere; but most ofthe latter remainedat or about the placeAv h e r e the aphisswarm Avas first seen, and they Avere still there at swarm decreased rapidly all day, until just before sunsetit was difiicult to find even a few specimens of the birds remained until it Avas nearly dark, for they Averestill finding a fcAV insects on the hig
. Useful birds and their protection. Containing brief descriptions of the more common and useful species of Massachusetts, with accounts of their food habits, and a chapter on the means of attracting and protecting birds . were pursuing themthere; but most ofthe latter remainedat or about the placeAv h e r e the aphisswarm Avas first seen, and they Avere still there at swarm decreased rapidly all day, until just before sunsetit was difiicult to find even a few specimens of the birds remained until it Avas nearly dark, for they Averestill finding a fcAV insects on the higher branches. The plantlice I had secured for identification Avere destroyed or lib-erated during the night, probably by a deer mouse whichfrequented the camp ; so the next morning at sunrise I wentto the trees to look for more specimens. The birds, Iioaa-ever, AA^ere there before me, and I Avas unable to find a singleaphis on the trees. The last bird to linger Avas more suc-cessful than I, for it Avas still findins^ a fcAv : but it soon graveup the eftbrt, and left for more fruitful fields. Probably afcAv insects escaped by flight; Init in examining the localityin 1905 I could not find one. The apparently complete. Figr. 29. — Warblers destroying a swarm of plant lice. 72 USEFUL BIRDS. destruction of these insects may have been due in part tothe hard winter that ensued, but the effect produced by thebirds was most obvious. Such instances of the quelling of insect outbreaks by birdsare noticeable, but the regulative influence steadily andperennially exerted b}^ them, which tends to keep hundredsof species of injurious insects below the point where theirinjury to trees and plants would become apparent, is veryseldom appreciated. THE INCREASE OF INJURIOUS INSECTS FOLLOWINGTHE DESTRUCTION OF BIRDS. Many cases have been noted where the destruction of birdshas been followed by an immediate increase in the numbersof injurious insects. Frederick the Great, king of Prussia,being part
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbirds, bookyear1913
