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 shelflike girdles develop.
McAtee (1911) gives a long list of trees attacked by the bird. Summarizing, 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 interest are by no means confined to the external disfiguration, the weakening, or killing of trees. Indeed in the aggregate sapsuckers inflict much greater financial 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 a quarter dollars.” He continues: “Sapsuckers do not prey upon any especially destructive insects and do comparatively little to offset the damage they inflict. Hence the yellow-bellied sapsucker * * * must be included in the class of injurious species.”
The situation is quite different on the breeding ground. Here the birds resort to a group of trees, and confine their feeding activities almost exclusively to them. Frank Bolles (1891), in his study of the bird in the region about Mount Chocorua, N. H., terms these stations “orchards.” He describes one of them as consisting “of about a dozen canoe birches and red maples, most of which were dead, some decayed and fallen. The tree most recently tapped was a red maple about forty feet high and two feet through at the butt.” Of another “orchard,” half a mile away, he says: “The tree in use last year was nearly dead. Two neighboring birches showing scars of earlier years were quite dead. All stood on the crest of a kame. About three rods along the ridge to the eastward a red oak and two or three canoe birches were in use by the birds.” This report shows that sapsuckers undoubtedly cause the death of many trees as they return to their “orchards” year after year, but most of these trees are of small value, especially in the heavily forested regions where the birds commonly breed.
Bolles (1891) also notes the association of the sapsuckers with the ruby-throated hummingbirds, which were attracted to the pits by the running sap. In the main, hosts and guests got along well enough together, although attacks occurred on both sides from time to time. He says: “My notes refer again and again to the spiteful treatment of the Hummers at Orchard No. 1. On the other hand at Orchard No. 2 they say ‘Male and young one dipping. Hummer comes in and dips several times between them and they offer no objection.’”
Major Bendire (1895), half in jest, we may presume, brings an accusation of inebriety against the sapsucker in these words:
That it should be fond of the sweet sap of trees does not surprise me, as this contains considerable nourishment, and likewise attracts a good many insects, which the birds eat; but it is not so easy to account for its especial predilection for the sap of the mountain ash, which has a decidedly bitter taste, and I believe possesses intoxicating properties, unless it be taken for the latter purpose; and the fact that after drinking freely of the sap of this tree it may often be seen clinging to the trunk for hours at a time, as if stupefied, seems to confirm this view. It is well known that some of our birds indulge in such disreputable practices, and possibly this species must be included in the number, as there are sots among birds as well as among the genus Homo.