Almost all purple martins in the East now nest in birdhouses put up especially for them. Martin housing has a long history. Some Native American tribes reportedly hung up hollow gourds around their villages to attract these birds. Purple martins migrate to South America for the winter, but before leaving, they may gather to roost in groups of thousands in late summer.
Their conservation status is showing a deep decline on the East Coast of the United States. There is no known reason for this decline, but competition with starlings for nesting sites may be involved.
I see more and more of these and similar types of "high rises" in our area.