The range map of tree swallows from the Cornell Lab of Ornithology’s All About Birds site shows the breeding range in orange, the migration range in yellow, and the winter (non-breeding) range in blue. They are cavity nesters, and if you live in their nesting zone, you may be able to attract them to your back yard. Here on Dewees Island, we participated in an experiment to see if we could attract them to a string of bird boxes on our berm, but we were unsuccessful in attracting them this much further south of their normal nesting range.
We were lucky to get to watch some breeding pairs and their young this summer in Montana. There is a series of nest boxes ringing a pond, and we delighted in watching them feed their young and bathe in the pond.