Helen Rodriguez doubled her patients Thursday at the intensive care unit of the Humane Society of Southeast Missouri.

Five ducks from the Capaha Park Lagoon were brought to the clinic after park workers discovered they were ill. All the animals were limp and lifeless but no one knows why. Five birds already have died.

We don't know the cause, so I'd hate to speculate," said Mark Sullivan, park supervisor with the Cape Girardeau Parks and Recreation Department.

Rumors are flying even if the ducks aren't. Some people have called the parks department and police saying that the ducks were poisoned; others think the sickness is caused by bacteria, overpopulation or bad diets.

About 20 ducks live at the park, although there is no definite count. Most of them are wild and migrate to the area to hatch eggs in the spring, which adds to the flock. Others were once pets and abandoned. The ducks feed on bread crumbs and handouts from visitors during the summer. The city feeds them during the winter.

Animal-control officers for the city found three dead birds in the water and captured another sick duck last week. It was taken to the Humane Society.

As many of the ducks that could be captured Thursday were taken to the Humane Society. Others that seemed healthy were allowed to stay. Park workers will check the birds again today to see if more have become ill.

"When we took him in, he didn't have control of his head muscle and couldn't move his feet," Rodriguez said of the sick duck, adding that the first 24 hours are critical.

Rodriguez didn't treat the bird with any antibiotics or ointments; just a bath.

A week after he arrived, the duck returned to his old self. He hisses and bites at her hand when Rodriguez cleans his cage or puts food in his dish. "Now he's ready for a home."

The duck will not be returned to his former home at Capaha Park; instead he is ready for adoption. The Humane Society already has a list of people who want to be considered as homes for the ducks.

"We have a wish list for almost anything that can be adopted at the Humane Society," Rodriguez said. The list includes every animal from ducks to goats and pot-bellied pigs.

Ducks are a rare site at the Humane Society. Even veterinary clinics rarely see the birds, although one clinic is performing an autopsy on a dead duck. Since the clinics rarely treat the animals, it is difficult to determine what is causing the illness, said an employee at Cape Small Animal Clinic.

One veterinarian thinks the sick ducks have been affected by a bacteria, said Jhan White, Humane Society administrator.

With the rising algae growth at the lagoon, a bacterial infection is a possibility, park workers say. But the algae has been treated with colorants designed to reduce growth.

"The label read that it is not harmful to fish or wildlife," Sullivan said, adding that more colorant was added to the water again Wednesday.

Algae growth at the lagoon is a constant problem for the parks department. "Some years it's worse, but part of that has to do with rainfall, heat and humidity," he said, explaining that the algae often causes the water to smell.

The lagoon, about 3.1 acres of water, holds storm-water runoff from streets and drains around Capaha Park. It does not receive any fresh water except when it rains.