58 WOODPECKERS IN RELATION TO TREES. 



The condition in wood of various kinds resulting from the everywhere common 

 work of the class of woodpeckers known as sapsuckers in the bark of forest and 

 cultivated trees has been the subject of special interest to me for mauy years, and 

 my work on forest insects has naturally offered a good opportunity for observations 

 and the collecting of specimens. The material collected represents some 40 species 

 of forest trees of many genera and families and from widely differing sections of the 

 country. 



It appears that the object of the sapsucker working in the bark of living trees is to 

 secure both liquid and solid food from the sap, cambium, and bast, and not for the 

 purpose of collecting insects, or at least not primarily for that purpose. The punc- 

 tures in the bark vary in size, form, and arrangement according to the species of tree 

 and the character of the food furnished. In the pine, spruce, hemlock, juniper, and 

 probably in all conifers, the desirable substance is furnished by the living bast tissue 

 and cambium, while the wood yields resin instead of sap; therefore the birds have no 

 occasion to puncture the outer wood ring and very rarely do so, whereas in maple, 

 walnut, hickory, and such trees as furnish at certain times of the year a profuse flow 

 of saccharine sap from the sapwood the outer ring of wood is generally punctured. 

 In the former the wounds are usually broad, often connected, and arranged in longi- 

 tudinal rows, 1 while in the latter they are narrow, funnel-shaped, rarely joining, and 

 arranged in transverse rows. The method of healing of these wounds is quite variable, 

 being influenced not only by the character of the wound but by the species or class 

 of trees in which they occur. The resulting defective or ornamental conditions and 

 subsequent annual layers of wood also vary in character and economic importance 

 with different kinds of trees and commercial products. 



The way in which sapsucker pecks are healed and the character- 

 istic blemishes and ornamental effects produced may best be under- 

 stood by the detailed consideration of these effects in a tree in which 

 they are well marked. For this purpose the sugar or hard maple 2 

 (Acer saccharum) is selected, a favorite tree of the sapsuckers and 

 one often seriously injured by them. The punctures sometimes 

 penetrate only to the sapwood, but generally they pierce one or 

 more animal rings. Whatever the character of the original wound, 

 more or less staining, varying from light yellow to dark brown in 

 color, takes place in its vicinity and sometimes extends several inches 

 up and down the grain. The greater the injury to the sapwood the 

 more extensive is the stain. When the sapsucker's drill extends 

 only to the sapwood, distortion of the wood healing the wound is 

 usually at a minimum. It can make excess growth only by bulging 

 out into the hole in the bark. Upon the extent of this swelling 

 depends the amount of abnormality in succeeding annual rings. 



Figure 9A of the excellent series furnished by Dr. Hopkins illus- 

 trates tliis type of healing. Here the excess growth was small and 

 would probably have been smoothly covered by the next annual 

 layer, though a second stain would have been produced owing to 



1 Probably the contour of the bark has much to do with the arrangement of punctures. Conifers often 

 bave very thick bark but with longitudinal cracks where the wood can be more quickly reached. Ver 

 tical series of pecks occur on deciduous trees also, especially upon those having long ridges or strips of thick 

 bark with furrows between 



-The specimens of hard maple here discussed were collected al Morgunlown, W. Ya. ( Hopkins), and in 

 Illinois ( F 26498) 



