RACHEL MARTIN, HOST:
Tonight in Rochester, Minn., residents will look to the sky and see some very unwelcome guests - thousands of crows threatening to shower waste on the city's downtown. As Minnesota Public Radio's Catharine Richert reports, chasing them away falls to a dedicated band of city workers.
CATHARINE RICHERT, BYLINE: If you're in downtown Rochester around dusk tonight and nearly every night this winter, you'll see this - thousands of black crows animating the night sky, flying in from all directions and calling to each other as they look for places to perch.
(SOUNDBITE OF CROWS CAWING)
RICHERT: The crows come here every winter and, with them, their poop. Left unchecked, all that crow waste could create a mess for city residents, as well as staff and patients at the sprawling Mayo Clinic campus.
BARRY WUTSCHKE: It's a constant battle to keep the sidewalks clean, to keep the cars clean.
RICHERT: That's Barry Wutschke. He's among a handful of city employees standing in the way of the poopy chaos every night, all winter.
WUTSCHKE: Just because it is such a problem.
RICHERT: It's gross.
WUTSCHKE: It is gross. And they have tried banging pots and pans together. They were netting the trees. And just nothing seemed to be working until we finally went to using starter pistols and green laser beams.
RICHERT: The crow patrol's cache of tools also includes a distress call machine that sounds like this.
(SOUNDBITE OF BIRDS CAWING)
RICHERT: Crows are big birds. They average about 17 inches long with a wingspan that can stretch to 3 feet. They're widely considered to be among the world's most intelligent birds. They prefer grassy open areas where they can forge for grains, nuts and even small animals. This night, the crows are just starting to arrive for the season.
So Barry Wutschke and his team will spend a lot of time figuring out where the crows congregate before swarming downtown. Naturally, it's the local cemetery. And it's noisy here, as thousands of crows perch in trees, cutting sharp silhouettes against the gray, late fall sky. We stop there to test the crows' reaction to the starter pistol.
(SOUNDBITE OF GUNSHOT)
RICHERT: They take off instantly. Kaeli Swift studies crows at the University of Washington and is amused to hear that they congregate in Rochester Cemetery.
KAELI SWIFT: It's a very convenient coincidence, (laughter) but it has a lot less to do with crows intuiting the function of cemeteries as it does - cemeteries just make really nice staging areas.
RICHERT: Swift says big, loud crow gatherings happen right before the birds head to their roosts to sleep. The gatherings likely serve a social purpose.
SWIFT: Maybe it is a way for crows to meet potential mates, for example, or reconnect with individuals that they haven't seen for a long time.
RICHERT: But it's something of a mystery as to why crows flock to urban centers in the winter. Swift says one possibility is that the environment provides warmth on cold Minnesota nights. But she says crows will eventually learn that starter guns and lasers signal danger. Back in Rochester, parks employee Don Yust is patrolling a street of popular restaurants and bars.
DON YUST: This was the hot spot last night.
RICHERT: He spots a tree filled with crows and blares a cacophony of crow calls from the back of his truck. It doesn't work, so he shines a laser at them, but only a few fly off. Finally, Yust whips out his last resort - his starter gun.
(SOUNDBITE OF GUNFIRE)
RICHERT: That scares all but one bird.
YUST: You'll get that stubborn one that will not leave no matter what you do. It's like, I've found my home for the night. Leave me alone.
RICHERT: It may take a few weeks or longer, but Yust says the crows will eventually learn to stay on the outskirts of downtown, at least for this winter. For NPR News, I'm Catharine Richert in Rochester, Minn.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.