YELLOW-BELLIED SAPSUCKER 135 



and there is no difficulty in recognizing the work as that of sapsuckers, for 

 no other woodpecker makes anything like it on sound, living trees. 



All holes, grooves, or irregular openings made by sapsuckers penetrate at 

 least to the outermost layer of sapwood or nongrowing part of the tree. This 

 results in the removal of the exterior rough bark, the delicate inner bark 

 or bast, and the cambium. Since the elaborated sap (upon which the growth 

 of trees depends) is conveyed and stored in these layers, it is evident that 

 sapsuckers attack the trees in a vital part. Each ring of punctures severs 

 at its particular level part of the sap-carrying vessels, another ring made 

 above destroys others, and so the process continues until in extreme cases 

 circulation of elaborated sap stops and the tree dies. When the injury to the 

 vital tissues is not carried so far, only a limb here and there may die, or the 

 tree may only have its vitality lowered for a few years. If the attacks cease, 

 it may completely recover. * * * 



Recovery, however, does not mean that the tree has escaped permanent 

 injury. Patches of cambium of varying size may be killed. Growth ceases at 

 these points and the dead and discolored areas are finally covered by wood and 

 bark. Until this process is completed, the tree is disfigured by pits with dead 

 bark and wood at the bottom, and even when completely healed, the spot 

 remains a source of weakness. In fact, all sapsucker pecking is followed by 

 more or less rotting and consequent weakening of the wood, and renders trees 

 more liable to be broken by the wind or other causes. 



Sapsucker injuries usually stimulate growth of the wood layers at the points 

 attacked, so that they become much thicker than usual. This results in a 

 slight swelling of the bark, and when the birds reopen the old wounds year 

 after year, as they habitually do, succeeding wood layers make excess growth 

 and in time shelflUce girdles develop. 



McAtee (1911) gives a long list of trees attacked by the bird. Sum- 

 marizing, he says: "Condensing the information contained in the 

 foregoing lists, we find that the yellow-bellied sapsucker attacks no 

 fewer than 246 species of native trees and 6 vines, besides 31 kinds of 

 introduced trees. Twenty-nine of these trees and 1 vine are known to 

 be sometimes killed and 28 others are much disfigured or seriously 

 reduced in vitality." 



Of "the effects of sapsucker work on lumber and finished wood 

 products" he says: 



Those relations of sapsuckers to trees which are detrimental to man's in- 

 terest are by no means confined to the external disfiguration, the weakening, or 

 killing of trees. Indeed in the aggregate sapsuckers iufiict much greater finan- 

 cial loss by rendering defective the wood of the far larger number of trees 

 which they work upon moderately but do not kill. Blemishes, reducing the 

 value, appear in the lumber from such trees and in the various articles into 

 which it is manufactured. 



These defects consist of distortion of the grain, formation of knotty growths 

 and cavities in the wood, extensive staining, fat streaks, resin deposits, and 

 other blemishes. All of them result from injuries to the cambium, their variety 

 being due to the differences in the healing. Besides blemishes, ornamental 

 effects are sometimes produced during the healing of sapsucker wounds, such 

 as small sound stains, curly grain, and a form of bird's-eye. 



McAtee (1911) estimates that "the annual loss for the whole United 

 States [from the impairment of lumber] is more than a million and 



