Nest: Yellow-bellied sapsuckers usually nest in cavities in snags or live trees with rotten heartwood. Aspen seems to be the preferred species (Howell 1952, Lawrence 1967, Kilham 1971), but nests have also been found in ponderosa pine, birch, elm, butternut, cottonwood, alder, willow, beech, maple, and fir (Bent 1939). Kilham (1971) noted that nest trees were often infected by the _Fomes_ fungus. Nest height varies from 5 to 70 feet above ground. The same nest tree is often used repeatedly, but a new cavity is excavated each year. Food: Sap is eaten throughout the year by the yellow-bellied sapsucker, but the amount taken and tree species used vary seasonally (Tate 1973, Lawrence 1967). The birds regularly tap one or two “favorite trees” in their area; Oliver (1970) found that these tend to be trees which have been wounded (by logging, porcupines, etc.). About 80 percent of the insect food taken consists of ants (McAtee 1911). Other insects in their diet include beetles and wasps, but none of the woodboring larvae. The fruits of dogwood, black alder, Virginia creeper, and blackberries are included in the small portion of vegetable matter eaten (Bent 1939). Williamson’s sapsucker _Sphyrapicus thyroideus_ L 8¼″ [Illustration] Habitat: This sapsucker prefers mixed conifer-hardwood forests of the Rocky Mountain region but also inhabits the subalpine spruce-fir-lodgepole zone, and ponderosa pine, Douglas-fir, and aspen forests. Nest: The choice of tree species for nesting seems to differ between regions. Bent (1939), Packard (1945), Bailey and Niedrach (1965), Burleigh (1972), and Jackman (1975) reported Williamson’s sapsuckers nesting primarily in conifers. Other authors (Rasmussen 1941, Hubbard 1965, Tatschl 1967, Ligon 1961, Crockett and Hadow 1975) found a preference for aspens. Of 57 nests in Colorado examined by Crockett and Hadow (1975), 49 were in aspens, especially aspens infected by the _Fomes_ fungus; where pines were used, there were no suitable aspen sites nearby. In Arizona, we found 17 nests in aspen snags, 3 in aspens with dead tops, and 1 nest in a live aspen. Food: The diet of Williamson’s sapsuckers is made up of 87 percent animal and 13 percent vegetable material (Bent 1939). Most of the animal food taken is ants, and most of the vegetable material is cambium. Like the yellow-bellied sapsucker, the Williamson’s sapsucker feeds on sap, especially in spring, and picks out “favorite trees” which it taps regularly (Oliver 1970). Hairy woodpecker _Picoides villosus_ L 7½″ [Illustration] Habitat: Hairy woodpeckers are residents of nearly all types of forest from central Canada south.