NASHVILLE, Tennessee (REUTERS) - Millions of birds have descended on a small Kentucky city this winter, fouling the landscape, scaring pets and raising the risk for disease in a real-life version of Alfred Hitchcock's horror film, The Birds.
The blackbirds and European starlings blacken the sky of Hopkinsville, Kentucky, before roosting at dusk, turn the landscape white with bird poop, and the disease they carry can kill a dog and sicken humans.
"I have seen them come in, and there are enough that if the sun is just right, they'll cloud your vision of the sun," said Hopkinsville-Christian County historian William Turner. "I estimate there are millions of them."
Mr David Chiles, president of the Little River Audubon Society, said the fact that migratory flocks are roosting in the city rather than flying further south is tied to climate warming.
"The weather, the climate plays a big role," said Mr Chiles, the bird enthusiast who also teaches biology at Hopkinsville High School.
"They somehow establish a roost south of where the ground is frozen solid," he explained. "They are ground feeders, feeding on leftover crops and insects. If the fields are frozen solid, they can't feed."
Although the birds have not turned on humans as in the classic 1963 Hitchcock movie featuring vicious attacks on people in a small northern California town, the city has taken defensive measures.
The south-central Kentucky city of 35,000 people, about an hour north of Nashville, has hired a pest control company to get rid of the interlopers.
Mr Henry Jako, general manager of McGee Pest Control, said crews use air cannons and "bird-bangers", similar to bottle rocket fireworks aimed into the trees where the birds roost. The artillery attacks are disturbing some locals, as well as the birds.
"It scares my little dog to death," said Christian County Judge-Executive Steve Tribble. "I don't know what it does other than move the birds from one tree to the next."
Mr Jako said in the worst-affected neighbourhoods, multiple cannons and consecutive blasts are being used to keep the birds moving. When they fly away, the birds leave behind a huge volume of excrement.
"I've got an apple tree that has almost turned white," Mr Tribble said. "Any vehicle parked outside is covered up. I guess it's good for folks that have car washes."
Historian Turner said the blackbird invasion this year is the worst he has witnessed since the late 1970s, when Hopkinsville suffered a similar bird blitz.
"We aren't seeing the temperatures go as low as zero like we used to. Now, we very often don't even see temperatures in the teens around here," Mr Jako said.
"If the birds are comfortable, they are going to stay around," he added.
The birds also pose a serious health hazard because their droppings can carry a fungal disease called histoplasmosis, which can cause lung infections and symptoms similar to pneumonia, according to the Centres for Disease Control website.
"It does become a matter of public health," said Dr Wade Northington, director of the Murray State University Breathitt Veterinary Centre, an animal disease diagnostic facility whose territory covers a 322km radius from Hopkinsville, including parts of Tennessee, Illinois and Indiana.
"The blackbirds are able to harbour this organism... so it can be shed in their droppings and it becomes a problem, especially where they tend to roost in extremely high numbers," he said.
It can cause illness in humans, and is particularly dangerous for people with compromised immune systems or respiratory ailments, he said. It can be fatal for canines.
Mr Turner, who suffered histoplasmosis decades ago after excavating family property that once held a chicken coop, describes the disease as debilitating. "I didn't have any energy, and I didn't have much appetite and lost weight," he said.
The droppings contaminate the soil, making it unhealthy for years. It is a worry for dog owners, said Dr Northington.
"It can be very expensive and take months to get it arrested and get an animal cured from it," h3 said. "The disease is very prevalent in our area."