By far the most common swallow we saw all along our journey.
Male
Using a natural nest hole though almost every "Bluebird Nest box" we saw on our trip had Tree Swallows in them.
Preening those all-important feathers
Migrating and wintering Tree Swallows can form enormous flocks numbering in the hundreds of thousands. They gather about an hour before sunset and form a dense cloud above a roost site (such as a cattail marsh like we saw at Horicon Marsh NWR in Wisconsin), swirling around like a living tornado. With each pass, more birds drop down until they are all settled on the roost. Several in the above moon shot were a little late.
Female