18 WOODPECKERS IN RELATION TO TREES. 



is no doubt that cambium, bast, and sap are depended upon by sap- 

 suckers as staple diet. 



The results of sapsucker attacks on trees are so uniform and char- 

 acteristic as to be distinguished easily from the work of other wood- 

 peckers. Sapsucker holes are drilled clear through the bark and 

 cambium and often into the wood. They vary in outline from cir- 

 cular to squarish elliptical, in the latter case usually having the 

 longer diameter across the limb or trunk. Generally they are ar- 

 ranged in rings or partial rings around the trunk, but they often fall 

 into vertical series. Deeply-cut holes arranged with such regularity 

 are made only by sapsuckers. 



After the original pattern of holes is completed, the sapsuckers 

 often continue their work, taking out the bark between holes until 

 sometimes large areas are cleanly removed. This often occurs on 

 small limbs or trunks, where long strips of bark up and down the 

 tree are removed, leaving narrow strings between. This effect is also 

 produced by continually enlarging single punctures by excavating at 

 the upper end (PL V, fig. 4), which is done to secure fresh inner bark 

 and a constant supply of sap. Occasionally, after a tree has been 

 checkered or grooved after the above-described systematic methods, 

 it may be barked indiscriminately, leaving only ragged patches of 

 bark. (PL V, fig. 5.) Even in such cases, however, traces of the 

 regularly arranged punctures are likely to remain, 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 m 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 Antality lowered for a 

 few years. If the attacks cease, it may completely recover. 



EFFECTS OF SAPSUCKER WORK ON THE EXTERNAL APPEAR- 

 ANCE OF TREES. 



Recovery, however, does not mean that the tree has escaped per- 

 manent injury. Patches of cambium of varying size may be killed. 

 Growth ceases at these points and the dead and discolored areas are 



