Kentucky City Fights Migratory Bird Invasion With Air Cannons, Lasers

Audie Cornish talks with Geoff LaBaron, an ornithologist with National Audubon Society, about a strange blackbird invasion in the town of Hopkinsville, Ky.

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AUDIE CORNISH, HOST:

As cardinals flock to Rome, blackbirds and starlings are flocking to Hopkinsville, Kentucky. Yes, we couldn't help ourselves with that transition. And the hills are alive with the sounds of air cannons. The cannons were brought in to disperse hundreds of thousands of birds roosting in trees, filling the skies, blocking the sun.

(SOUNDBITE OF CANNONS)

CORNISH: The cannons were brought in to disperse hundreds of thousands of birds roosting in trees, filling the skies, blocking the sun.

BOBBY HAILE: Well, they usually come in about 4:30 or 5:00, and they just come in in droves. They don't just come at one time. They circle around and look for a landing place. And then here comes another maybe 1,000 birds, and the sky almost gets black. The sky is just full of them.

CORNISH: That's Hopkinsville resident Bobby Haile, a retired dentist. And while it's not uncommon for migratory flocks to make a pit stop in Haile's area, the sheer scope of this visit is causing some problems. With us to explain a bit more about this troublesome bird summit in Hopkinsville, Kentucky is Geoff LeBaron, an ornithologist with National Audubon Society. Welcome, Geoff.

GEOFF LEBARON: Glad to be here.

CORNISH: So forgive me, but this sounds a little like the scene from the Alfred Hitchcock movie "The Birds." What's really going on here?

LEBARON: Well, what's really going on is that these large flocks of blackbirds and generically we call a mixed species flock, usually blackbirds, linnets, redwing blackbirds, common grackles, brown-headed cowbirds and also European starlings, and they tend to congregate in what we call winter roosts during the offseason. And what's happening right now is these birds are actually moving northward up to their breeding grounds. I'm actually up here in New England, and our first redwing blackbirds just arrived here in the last week.

So they're sort of - the redwings are really the true harbingers of spring up here. But what's happening in areas like Hopkinsville is these roosts happen to be right there right now.

CORNISH: You've seen roosts of this size before. What do they look like?

LEBARON: Well, as the local person said, it's really impressive when the birds are coming in in the evening. It can be like a river or several rivers of birds that are just sort of pouring into a wood lot. And it's a phenomenal and exciting and sort of, in many ways, wonderful sight.

CORNISH: So what do we know about the factors that actually draw birds together in these numbers?

LEBARON: Well, blackbirds, by their biology, congregate in huge flocks in the winter. It helps the individual bird from possibility of predation because if a predator comes in, that predator would have to decide which particular bird to go after. Also, when food resources are often patchy or less available in the winter, it's advantageous to forage more as a group. And that's what the blackbirds really do.

They, you know, they forge around during the daytime in flocks of hundreds or maybe a few thousand, and then those individual flocks start to sort of coalesce into a given area that's relatively protected and they form these tremendous roosts at night.

CORNISH: So what makes this particular roost unusual? I mean, is it the size?

LEBARON: It's not unusual from the biological standpoint. This is what blackbirds and starlings do during the winter and during migration. What is slightly unusual is just the fact that it happens to be in town where people are getting to experience it in all its wonder and experience that people are getting right now.

CORNISH: Now, finally, the town of Hopkinsville is trying to scare these birds off with cannons, and I hear some kind of like laser light. Any sense for how well those techniques work?

LEBARON: Well, the birds want to - they don't want to be disturbed at night. Part of their reasoning for selecting an area is because they want, A, protection but also some semblance of quiet. It's likely or possible anyway that that sort of repeated disturbance, at least on some nights, will cause them to move. But the reality is they're going to move anyway.

I mean, these birds are just in that number in the area for a short period of time. You know, they're going to disperse really out all over North America to breed. So the disturbance can encourage them to move, but they're probably going to move on their own anyway.

CORNISH: Geoff LeBaron, he is from the National Audubon Society. Geoff, thank you so much for talking with us.

LEBARON: You're entirely welcome.

CORNISH: This is NPR News.

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