ST. LOUIS (AP) - If you play it, they will come. Eventually.
The purple martin, North America's largest swallow, has a cozy relationship with humans.
But they were generally missing from the St. Louis Zoo until May, when three mating pairs made their home in a tall house on a tiny island in a small cove at the park.
And "the song" may have done the trick.
Officially titled "The Dawn Song," it was recorded in 1989 in Oregon by the Cornell Lab of Ornithology. The tune basically is a looped recording of a male purple martin singing a song that gets quicker as dawn approaches.
"We played it every morning, from 3:30 to 6:30," said bird keeper Matt Schamberger, a Belleville native who now lives in St. Louis and has been with the zoo for four years.
"Actually, we got the A.V. guy to set it on a timer to go off automatically," he said. "We like purple martins, sure, but not enough to be here at 3:30 every morning."
The "we" includes Jim Deters, a Warrenton resident and a 27-year veteran of bird-keeping at the zoo, the St. Louis Post-Dispatch (http://bit.ly/28xJUAQ ) reports.
"Last year was our first, and we didn't get (the house) up until May," Deters said. "We did get what they call 'scouts,' which are older adult birds who come by and look for good nesting locations. But that was it.
"But this year, we moved the house to a better spot and played the song and so far we've been able to identify three mating pairs," Deters said with quiet pride.
One of the species' most endearing habits is that they come back to the same nest for years, and often make that return on the same date. (The swallows of Capistrano, right?)
But both keepers wonder about next year's return, given that the pairs here now did not show up until early May.
"Migratory patterns (the birds start in South America) say they're supposed to get here in late April, so we played the song for a solid month, mid-March to mid-April," Schamberger said.
"But ours didn't. We kind of thought we weren't going to get any, and then they show up in May," Schamberger said.
The pair of keepers said they would love to get up to 12 pairs in the 24-condo birdhouse.
Schamberger said the pairs now seem to be occupying two condos each. "It's like they have a home and a vacation home in the same birdhouse."
Michael Macek, the zoo's curator of birds, said he wanted to create an environment for a species that is easily one of the most popular with bird lovers.
"Purple martins have this unique connection to humans. People just seem to like them and value them," Macek said, noting that Native Americans began building homes for the birds several hundred years ago.
The tribes created houses from hollowed-out gourds, painted them white and hung them on tall poles. Research indicates that the tribes may have appreciated, among other traits, their voracious appetite for flying insects.
Macek said the conspicuous nature of a purple martin house has helped popularize the species: They are built on tall poles, between 12 and 20 feet off the ground. They have multiple compartments, called "condos" or "apartments."
Deters said the height stems from the species' healthy fear of predators.
"They like it to stand alone, away from buildings and trees that could hide predators," Deters said. "And they even like the ground around the pole to be clear of any foliage, in case they're hiding in there."
Schamberger said the species is rare in its communal living.
"Most birds, including other swallows, build one small nest in a secluded place and don't want company. But martins seemed to like living in a crowd," he said.
Finally, people love the species' acrobatic flights and seemingly endless amount of energy.
"They're busy birds," Schamberger said. "They're always doing something."
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Information from: St. Louis Post-Dispatch, http://www.stltoday.com