Habitat: Ponderosa pine affords the favorite habitat for violet-green swallows (Bailey and Niedrach 1965), but they are also found in aspen-willow and spruce-aspen forests. They prefer open or broken woods or the edges of dense forests. Nest: Violet-green swallows nest in holes, cavities, and crevices in a variety of situations. Where birds are abundant, the demand for nest sites is sometimes greater than the supply, and practically any available cavity may be used. These swallows have been reported to use old nests of cliff swallows and even burrows of bank swallow (Bent 1942). Winternitz (1973) reported violet-greens using old woodpecker holes in live aspen as nesting sites, but in Arizona, we found them nesting primarily in old woodpecker holes in ponderosa pine snags. We found one in the dead top of an aspen, 5 in dead tops of ponderosa pine, and 26 in ponderosa pine snags. Nest heights ranged from 16 to 80 feet and averaged 43 feet. Food: Apparently, the diet of this species is exclusively insects taken on the wing. It includes leafhoppers, leaf bugs, flies, flying ants, and some wasps, bees, and beetles (Bent 1942). In Colorado, Baldwin (pers. comm.[7]) found that insects made up 99 percent of the stomach contents of six violet-green swallows. Flies were the most abundant insect found. Scolytid beetles, seed and leaf bugs, miscellaneous insects, and a few spiders were also found. Tree swallow _Iridoprocne bicolor_ L 5″ [Illustration] Habitat: Tree swallows breed throughout North America from the northern half of the United States north to the limit of tree growth. They are migrants throughout the Central and Southern states and winter primarily in Central America. Nest: Tree swallows prefer to nest in natural cavities and old woodpecker holes—usually near water. The lack of natural cavities, competition for existing cavities, and the availability of nest boxes, have resulted in a shift in nesting preferences to nest boxes in the eastern United States (Bent 1942, Low 1933, Whittle 1926). Bluebird boxes and purple martin houses are frequently used. Tree swallows are not colonial, but will nest within 7 feet of each other, if there are adequate meadows, marsh, or water area available for feeding (Whittle 1926). Woodpecker holes in aspen, spruce, and pine are the most common nest sites in the West (Bailey and Niedrach 1965). Food: This species is the first of the swallows to arrive in the north in the spring, and the last to depart in the fall. Because tree swallows can subsist on seeds and berries, they are not as dependent upon insects as are other swallows. They are partial to waxmyrtle and bayberry where these are available. Plant food proportions in the diet are 1 percent in spring, 21 percent in summer, 29 percent in fall, and 30 percent in winter (Martin et al. 1951, Forbush and May 1939). Purple martin _Progne subis_ L 7″ [Illustration]