WOODPECKERS IN RELATION TO TREES AND WOOD 

 PRODUCTS. 



INTRODUCTION. 



Woodpeckers are peculiarly dependent upon trees, which furnish 

 them food, shelter, and cradles for their young. No birds are more 

 highly specialized nor more perfectly adapted to a particular mode 

 of life than are most woodpeckers to arboreal existence. Moreover, 

 as trees are important to woodpeckers, so are these birds important 

 to trees. Woodpeckers benefit trees by consuming many of the most 

 destructive forest pests, insects largely inaccessible to other birds. 

 In securing these insects, however, which constitute the bulk of their 

 food, and in making nests and shelter cavities, woodpeckers have 

 another significant economic relation to trees, for they remove bark 

 and wood from both dead and living trees. In the case of dead trees 

 little or no harm is done. When, however, they make excavations in 

 living trees, the birds destroy more or less of the cambium layer, 

 from which proceeds the growth of both wood and bark. Slight 

 injuries to the cambium result in distorted growth, but the destruction 

 of large areas may cause death. Since trees are exceedingly valuable 

 to man, the habits of birds whose relations to trees are so vital are 

 of much economic importance. 



It is the purpose of this bulletin to examine the evidence for and 

 against woodpeckers and to determine their status according to the 

 effect of their habits upon trees and wood products. Injuries by 

 woodpeckers are treated under two heads: (1) Damage by wood- 

 peckers in general; (2) injuries due almost exclusively to the three 

 species properly known as sapsuckers. 



DAMAGE BY WOODPECKERS IN GENERAL. 



This topic may be divided into two sections: Damage to trees, 

 and damage to wooden posts and structures. 



DAMAGE TO TREES. 



Primarily the work of woodpeckers on the hving parts of trees is 

 injurious. The important cambium layer is injured every time a 

 nest is excavated or an insect dug out. To what extent the various 



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