It was quiet and slightly chilly in the pre-dawn winter shadow of Diamond Head as Chris Cooper, a retired ship’s captain, reached up to pour birdseed into the feeders he’d built atop his garden fence. A screech broke the silence as a bright-green parrot wheeled against the sky.

“That’s the sentry,” said Cooper, 68, a buff, darkly tanned surfer whose shoulder-length white hair glimmered in the dim light. “He goes and tells the other parrots it’s all clear. Then they swoop on in.”

In a moment, dozens of the hook-beaked, long-tailed birds were flapping and kvetching at the feeders or surveying the scene from telephone wires.

“I counted 35 of ’em yesterday,” Cooper said.

They are gregarious and beautiful, big, streamlined birds that are a parrot subspecies known as rose-ringed parakeets. Across Oahu from Mililani to Waimanalo and the heart of downtown Honolulu, they streak and shriek overhead and chatter in the treetops, lending a touch of the exotic to urban and suburban neighborhoods.

They can be seen and heard at dusk, returning to their overnight roosts in tall trees, and at daybreak, when they fly abroad in search of food. They nest in the hollows of tree trunks, and while they primarily nest in the spring, they can be seen now exploring for suitable hollows.

And, as with many exotic species, the feral birds, which are native to India and escaped after being brought to Hawaii as caged pets, have the potential to become an intransigent agricultural pest and threat to endangered Hawaiian species.

In response to concerns expressed by a working group including farmers, the state Division of Forestry and Wildlife’s Kauai branch and the Kauai Invasive Species Committee, a bill seeking funds to study and explore ways to control rose-ringed parakeets was introduced by Rep. Derek Kawakami in the state Legislature last year. HB 772 was carried over and will be reintroduced in the current legislative session, Kawakami’s office said.

On Kauai, farmers and residents are complaining about parakeet predation of field corn and fruit trees. “Their large bills are designed to crack large seeds and nuts. They’re taking rambutan, longan, mango, lychee, papaya,” said Thomas Kaiakapu, Kauai wildlife manager for the Division of Forestry and Wildlife, part of the Department of Land and Natural Resources. “They fly in and land on a tree by the hundreds, and if nobody chases them away, they can demolish a tree of fruits in a matter of days.”

The birds wait until fruit or seed corn is ripe, “then they peel it open and eat it,” Kaiakapu said.

“One lychee farmer lost 70 to 80 percent of his crop last year,” said Jerry Ornellas, former president of the Kauai Farm Bureau, which has been receiving complaints about parrot predation going back to 2007. At first the incidents were limited to the large seed corn plantations on Kauai’s west side, Ornellas said, but in recent years they’ve been raiding trees on the island’s eastern shore.

Linda Kaialoa grows lychee and rambutan in her Kapaa backyard, which has been under siege by the parakeets for the past couple of years. She had a shock one day, she said, when a tree full of ripe, red rambutan suddenly turned white. “Then I saw that the parrots had peeled the tops off the fruits and eaten the flesh, leaving the hollowed-out shells still hanging on the stems.”

Bernard Machado, who tends fruit trees on his Wailua Homesteads lot, said he lost money last year “because the parrots came and ate so much rambutan.” This year, he said, he hopes to harvest the ripe fruit before the birds get to it, but “one tree, the whole top is gone already.”

The birds are smart and wary, Machado said; they avoid him and won’t eat food he puts out on the ground. “They can’t be trapped.”

The seed companies hire people to chase birds, Ornellas said, “but the backyard growers can’t afford that. It’s a huge problem.”

THE BIRDS, to put it mildly, have outlasted their welcome in most quarters. The state Department of Agriculture has banned importation of the rose-ringed parakeet as pets “because it is significantly harmful to agriculture,” said Keevin K. Minami, land vertebrates specialist for the Plant Quarantine Branch, in an email.

While farmers can attest to economic harm, no specific threat to Hawaii’s natural resources has been ascertained as yet, said Kaiakapu and his colleague Jason Misaki, Oahu district wildlife biologist for DLNR.

Kaiakapu and Misaki partly attributed the lack of evidence to the lack of funds for studying the parakeets’ diet, habitat, behavior and numbers. HB 722 would provide for such studies on Kauai.

At DLNR the parakeets “are considered injurious wildlife, which basically means that they have been identified as a harmful species,” Misaki said. DLNR protects endangered species, and there is concern the parakeets will compete with endangered native birds for habitat and food.

Thus far, “we only see them in urban areas and lowland forests, not yet in the upper forests where there are the most native species of birds and plants,” Misaki said. However, the elepaio, an endangered native bird, lives in the lowland forests, as does the amakihi, an endemic honeycreeper that is not classified as endangered, he noted.

The parakeets could also disperse seeds of invasive plants such as miconia and the albizia trees in which they commonly nest, said Bill Lucey, project manager for the Kauai Invasive Species Committee. “Albizia branches break off easily, and this creates hollows,” he explained.

“We’re concerned that they’re going to be moving invasive seeds into more natural areas that are dominated by native vegetation, so they could potentially be accelerating invasion of upper elevations with native plants,” Lucey said. Wildlife officials have seen the parakeets eating the seeds of native pritchardia (loulu palm) and koa trees, he added.

Another concern, noted in HB 722, is that the birds might spread diseases such as avian malaria and salmonella.

The DLNR says not to feed any wild birds, including rose-ringed parakeets, because it can lead to proliferation of alien species and expose native species to harm by making them trusting of and dependent on humans.

NUMBERS of wild rose-ringed parakeets appear to have been steadily increasing since they were first noticed flying about Honolulu in the 1930s, according to a study published by Bishop Museum in 2009. Although no official Oahu population count exists, “they are widespread around the island and number in the hundreds at least,” Misaki said.

At last count, in 2011, there were 2,000 rose-necked parakeets on Kauai, according to a study funded by agricultural companies and conducted by the Hilo branch of the U.S. Department of Agriculture’s National Wildlife Laboratory. The Kauai population is believed to have grown from a few birds released by a Lawai bed-and-breakfast during the 1960s.

“We could be moving into a J-curve growth,” Lucey said of the Kauai parakeet populations. “They’re established in England, where their reproduction rate is about 30 percent annually, and they’re a big problem there.”

In Honolulu, Cooper has observed his breakfast guests increase from “just a couple” to 35 parakeets since he started putting out bird food six years ago. “I figure they tell their buddies and so the news gets around,” he said.

On Oahu a central roosting place is in the trees along Punahou Street fronting the Shriners Hospital for Children and the Banyan Tree Plaza condominium. The parakeets that downtown Honolulu office workers see and hear flying mauka at pau hana time are heading for the Punahou Street roost, said Nicholas Kalodimos, who received his Master of Science degree in botany at the University of Hawaii and has been studying the birds for years. “When I first started watching them, in 2003-2005, there were about 100-150 parakeets. Now about 1,200 birds come there to roost,” Kalodimos said. The flocks seen in Kapiolani Park, Kalihi, Nuuanu and at Roosevelt High School all congregate at Punahou Street for the night, he has observed.

The birds are observing people, as well.

“They’re extremely intelligent animals,” Lucey said. “They recognize trucks, they recognize people. They’ll send two birds in and scout out a field looking for danger, and if there’s no danger, they’ll call the flock in to feed.”

Cooper can corroborate that. “When I go jogging in Kapiolani Park, they follow me,” he said with a laugh. While able to distinguish friend from foe, the rose-ringed parakeets’ most potent weapon may be their charm.