ROBERT SIEGEL, HOST:
Every summer migrating birds fly across the country - across the world without much fanfare. You might spot a flock of geese overhead but for the most part birds stay out of sight. For one species the exact opposite is true, their summer ritual happens in a very public place. From Austin, Texas, Luke Quinton reports from a place that isn't typical for bird watching. It is the parking lot of an abandoned shopping mall.
LUKE QUINTON, BYLINE: It's a hot summer night just before sunset and the lot should be empty but there are dozens of people here. Some have cameras, others carry umbrellas.
QUINTON: Hey Laurie. So, where are we going?
LAURIE FOSS: Over here, to the back row folks.
QUINTON: This is Laurie from the Travis County Audubon Society, it's a group of dedicated, maybe obsessive, birders. They're the reason people are here. Laurie's making the rounds.
FOSS: Hey, you here to see the martins?
STADLER: I got dragged out here.
FOSS: That's the spirit, all right. Do you know about purple martins?
ALICE STADLER: Not at all.
FOSS: Do you know that's who's fly around here already. They're starting to come in.
STADLER: They look purple to me, they look black.
QUINTON: That's teenager Alicia Stadler. She's not impressed yet.
FOSS: A lot of people think they're grackles, some people think they're bats. They have no idea what there here to see.
QUINTON: Purple martins are the largest swallows in North America. They spend most of they're time eating bugs in mid-flight. They're aerial acrobats. Foss points to the sky.
FOSS: But if you look, look up a beyond the birds that you can just see low down.
QUINTON: Hundreds of tiny triangular birds dot the sky, gliding leisurely on current. Then we focus our eyes farther up.
FOSS: There as high as you can see and higher still. They haven't all come down yet.
QUINTON: Now there are thousands flying in layers. This is our first glimpse of the alien invasion to come. The birds were eating all day, now they're waiting till the sun goes down. Even experienced birder Karen McBride, doesn't know what she's in for.
KAREN MCBRIDE: I'm expecting a few thousand but I'm not expecting tens of thousands. That would blow my mind.
QUINTON: Grade-schooler Anna Fulton is here for the second year.
ANNA FULTON: They get here kind of slowly but eventually it's like black. Like, the sky is filled with birds, it's pretty cool.
QUINTON: All of the sudden the sun goes down. It starts with a light chirping.
(SOUNDBITE OF BIRDS CHIRPING)
QUINTON: Then they come in swooping in huge currents above the trees, some just barely over our heads. I duck underneath the awning of a Jack-in-the-Box restaurant. Before coming out of the drive throw, just like, what is going on out here? Brian Frankie is here too. He's also dodging the bat guano.
BRIAN FRANKIE: That's wild. I can't believe they all just came down in these, like four trees. You can see the trees are like way down, they're all kind of flat from all the weight.
QUINTON: It turns out that there are about half a million purple martins here. That's according to the Audubon Society. Laurie Foss says this is one of the largest roosts in the country. The birds land here in groups of around 200.
FOSS: They can be related or they can be related by geography. Housing groups will gather with other housing groups that are near each other and they form a loose alliance.
QUINTON: Back by the trees Debbie Levine is standing with her family looking at the sky.
DEBBIE LEVINE: You know what it feels like? It feels like you're in a snow globe. Only instead of white it's black. Doesn't it?
QUINTON: This party happens every night until August. Then the martins trickle off on the way to the Amazon basin until next year. For NPR News I'm Luke Quinton in Austin.
AUDIE CORNISH, HOST:
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