Damage
Sapsuckers attack only living trees. In forested areas they have been observed feeding on a wide variety of deciduous and coniferous species. However, in prairie and urban areas where trees are planted for ornamental and shelterbelt purposes, they seem to prefer birches, Colorado spruce, Scots pine and Siberian elm.
The adult birds cause damage by pecking horizontal rows of regularly spaced, small, oval to squarish holes through the bark to the sapwood. Unlike other woodpeckers, sapsuckers do not drill these holes in search of grubs or worms on which to feed. Instead, the birds use their short brushlike tongues to drink the sap that oozes into the holes. They also eat the outer wood layers. As one row of holes becomes dry, another row is drilled, and so on. Rows of holes may extend for some distance up the trunk and heavier branches of the tree. Injury is usually most pronounced in the spring and early summer when sap pressure is greatest.
Damage varies considerably, depending on the persistence of attack. Lightly attacked trees usually make a complete recovery. On the other hand, branches girdled with several rows of holes are often permanently damaged, and smaller trees or tops of trees may be killed by severe attack in several successive years. Harmful insects and disease organisms may enter the tree by way of these holes, resulting in secondary damage. The characteristic holes made by sapsuckers and the subsequent staining or discoloration of the wood can be recognized many years after the attack.
Control
Control is difficult because the yellow-bellied sapsucker, like most other birds, is protected under the Migratory Birds Convention Act, and may not be killed or captured, or its eggs destroyed. Serious damage can be prevented to some extent by placing noisemakers and frightening devices (flutters) in affected trees. Wrapping the damaged areas on individual trees with strips of burlap or other protective material and leaving it in place from April to late summer when the birds are most active is also effective. Spraying the holes with pruning paint (a dressing in spray form) will reduce sap flow and prevent entry of insects and diseases. The holes should first be thoroughly cleaned of hardened sap and debris with a sharp knife. Varnishes, shellacs, and paints are not recommended as sealers because they have a toxic effect on the tree.
The cause
The yellow-bellied sapsucker [Sphyrapicus varius (L.)] is a small (20-23 cm) migratory member of the woodpecker family that is present throughout the summer. Although there are variations in coloration between individual birds, sapsuckers are readily identified by a long white stripe down their closed wings that is visible when they are perched on a tree. The mature male has a red crown and throat bordered by black, and the mature female a smaller red crown and a white throat. Both have white bands above and below the eye extending onto the neck, a black patch on the breast, and a yellowish-white abdomen. Young birds in juvenile plumage appear brown and have no black breast patch, but like the adults have the long white wing markings.
Sapsuckers usually nest in holes well above the ground in the heartwood of dead or partly dead trees located within easy flying distance of their selected feeding ground. Three to seven white eggs are laid per nest. Each pair of birds establishes a territory on which other sapsuckers do not trespass, and if the territory is productive a pair may return year after year to the same location. About 50% of the sapsucker's diet is composed of sap and sapwood. The remainder is wild berries, fruits, and flying insects attracted to the sap exuding from the holes drilled in the trees.
Source: V. Hildahl, Northern Forest Research Centre, Edmonton, Alberta