KAILUA — The gunshot killings of a dozen ducks at Hamakua Marsh last weekend has enraged residents, but state officials said the culling was necessary to protect native species and occurs frequently.

Residents said they were alarmed to learn that someone with a gun was at the marsh on Sunday shooting the wild birds that are loved and cherished by everyone who goes there.

"It was like coming home and finding your animals murdered," said Shawn Garliepp, owner of the Creekside lounge adjacent to the marsh on Hamakua Drive. "Everybody feeds them. They even come up and you can pet them."

Garliepp said she arrived early Sunday morning to open the bar for pro football fans because the games on the Mainland start at 7 a.m. Hawai'i time. She said she found blood stains in the parking lot and bullet casings.

People reported seeing a man with a gun picking up dead ducks and placing them in a container, she said. The bystanders said the man identified himself as being from the state Department of Land and Natural Resources.

Police were called, and even though the responding officers reportedly didn't know anything about the shooting, the practice has been going on for years and generally the station is notified ahead of time, said Michelle Yu, HPD spokeswoman.

Jason Misaki, DLNR wildlife biologist, said controlling the population of non-native fowl protects the native birds.

"The feral ducks take away habitat from our native birds," Misaki said. "They compete for food and space. They also hybridize with native ducks."

The shooter was under contract to the DLNR and works for the U.S. Department of Agriculture Wildlife Services Branch, which among other things helps control feral animals using strict safety standards, Misaki said.

One male mallard and 11 of the larger muscovy ducks were shot, Misaki said, adding that other methods were considered but this way is the best.

Trapping is difficult because native ducks can get caught as well, and moving ducks to another location only moves the problem. And more than likely, the birds will return after they are moved, he said.

"We do get a lot of calls from people concerned about the number of ducks within their area, so that's one reason we don't want to release them into other areas," Misaki said.

Hamakua Marsh covers about 22 acres and is home to the endangered Hawaiian moorhen, Hawaiian coot and Hawaiian stilt. There are about 10 stilt pairs, 10 coot pairs and 15 to 20 moorhen pairs, Misaki said.

"It's getting crowded already," he said. "Any more ducks in there is just going to take away habitat from our water birds."

The bird population is surveyed regularly, especially in the nesting season from late December through early summer, he said. Once the area has 10 to 15 non-native birds such as the mallards, someone is sent to remove them. It sometimes happens as often as every other month, Misaki said.

Adding to the population problem are people who feed the ducks, bringing more animals to the area, he said.

But Misaki said he understands the pleasure in feeding the birds. It's fun and kids love it but the repercussion is grave.

One resident said she worries that the shooter might be killing koloa ducks, which look like female mallards. But Misaki said only the distinctive male mallards are removed to avoid that error.

Still, Jan Cook said, shooting the birds seems harsh, and she doubts the marsh has reached its capacity. Cook said she has lived on Kaelepulu Pond in Enchanted Lake for 20 years and watched the patterns of waterfowl there and on the marsh and the population is stable.

"Why do we have to make them conform to our ways? Why don't we just leave nature alone because we seem to screw it up every time we touch it," she said.