  
Barn Swallows breed from Alaska
across Canada, throughout the United States, and south through
central Mexico. With the proliferation of human-provided nesting
sites, the North American Barn Swallow population has increased
in most places during the 20th century. Numbers are especially up
in the central and eastern United States. Barn Swallows show
strong fidelity to their natal site, most nesting within 20 miles
of their birthplace and some much closer. Members of a pair
typically stay together to raise a second brood and return in
successive years to the same nest site. If you have the right
habitat, barn swallows are easy to attract. A simple nesting
perch may be placed under the eaves, inside a garage or barn, or
on the side of a building.
Tree Swallows are found all across the continental United States
and Canada, and in parts of Alaska, as far north as cavities are
available, avoiding only the southeastern corner of the U.S. Tree
Swallows prefer open habitats, such as the edges of woods, and
areas near water, including marshes, shorelines and swamps. Tree
Swallows are quite tolerant of humans. Nesting is quite
synchronous in Tree Swallows; that is, females tend to begin
nesting within a week or 10 days, usually in April, of their
neighbors. Tree Swallows nest in natural tree cavities,
woodpecker holes and nest boxes. Tree Swallow houses should be
placed 5 to 15 feet high on a post or tree in open areas. They
should be spaced 30 to 100 feet apart with the entrance hole
facing east.
Violet-green Swallows are found from the Rocky Mountains west to
the Pacific coast. Their range spans from central Alaska and
central Canada south to the Mexico's highlands. Violet-green
Swallows prefer open, deciduous, or mixed coniferous-deciduous
forests containing ponderosa pine, aspen, willow and spruce
trees. In the northern part of its range, this species breeds at
lower elevations on the coast and in wooded canyons. In the
southern part of their range, they breed at higher elevations
(2,000 to 3,000 meters). Violet-green Swallows nest in cliff
crevices, natural tree cavities, woodpecker holes, in old nests
of Banks and Cliff Swallow, under the eaves of buildings, and in
nest boxes. They can nest in close association with Cliff
Swallows, Tree Swallows, White-throated Swifts, and Western
Bluebirds. One report documented a pair of Violet-greens
assisting a pair of Western Bluebirds in raising young. The
swallows guarded the nest and tended the bluebird nestlings, and
after the bluebirds fledged, the swallows used the nest site. In
the northern portion of their range, pair formation begins in
mid-April and breeding begins in late May. In the southern
portion, breeding begins in early May. Violet-green Swallow
houses should be placed 9 to 15 feet high in open or broken
deciduous or mixed deciduous-coniferous forests, wooded canyons,
or edges of dense forests.
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