The idea that purple martin “scouts” are on a reconnaissance mission to find suitable nesting territory, then report back to the flock is, like too much of what we hear about the natural world, a romanticized anthropogenic notion. The scouts are actually older birds returning to their nesting site. Martins have strong nest-site fidelity, and older birds return first. It may take four to six weeks before sub adults return to the site – perhaps giving the impression that these birds were led to the site by “scouts.”
Nest sites east of the Rockies are almost exclusively man-made. There appears to be a long, strong human-martin bond. Native Americans in the East hung gourds for purple martins before white settlers arrived. Birds west of the Rockies nest almost exclusively in abandoned woodpecker cavities. It seems standing snags in beaver ponds were/are preferred sites in the West.
Purple martins are large swallows reaching nearly 9 inches in length. The male is a dark, deep, rich blue above and below. He appears black at a distance. Females and juveniles are dark above with a whitish belly and grayish brown on the breast and throat.
Martins generally have one brood per year. When nesting is over – which could be as early as late May in the Deep South or as late as September in Canada – these gregarious creatures congregate in large roosts before starting their southern migration. One roost in Lake Murray, S.C. was reported to have more than 700,000 birds. It’s hard to tell what draws martins to a roost. Many are located over water, which would seem to protect against predators, but there are large roosts in urban areas like the Schumpert medical complex in downtown Shreveport, La. and Sharpstown Mall in Houston, Texas, to name a couple.
The Old North State is home to a large pre-migratory purple martin roost beneath the William B. Umstead Memorial Bridge (Old Manns Harbor) over Croatan Sound in Dare County. The roost is near the western end of the bridge and is home to around 100,000 purple martins. The roost generally peaks from around the end of July through the end of August when tens of thousands of martins funnel and swirl through the twilight vying for perches beneath the bridge.
No doubt, 99.9 percent of the Manns Harbor martins nested in man-made nests somewhere in the coastal plain of North Carolina. But these birds were fortunate to have another human benefactor. Alisa Esposito Lucash and her husband Chris were crossing the bridge one evening around dusk in 2001 when their car was enveloped by a mass of swirling martins.
The Lucashes slowed their car but Alisa recalled in an article, “…we watched horrified, while the van ahead of us drove full steam forward into a swirling wall of martins, seemingly unaware of the dead and maimed creatures it left in its wake.”
Esposito Lucash worked tirelessly and with friends created the Coastal Carolina Purple Martin Society. Their initial thought was an exclusion fence like one that protects roosting martins along the causeway across Lake Pontchartrain in New Orleans. But the Umstead Bridge wouldn’t support such a structure. The group didn’t quit and in 2007 with the help of N.C. DOT, Dare County Commissioners, then State Sen. Marc Basnight and others signs and flashing traffic lights were installed. While this solution is not as effective as a fence, Esposito Lucash noted, “When every car slows down, there’s not a bird killed,” she said. “It’s really completely related to motorists’ behavior and their willingness to slow down.”
Sightseeing and educational programs are offered every year to see the Manns Harbor martins.