By Laura Zuckerman

SALMON, Idaho (Reuters) - Idaho is planning to kill thousands of ravens to protect another bird whose eggs and chicks are among its prey, despite criticism that human development is a greater threat to the imperiled sage-grouse than the black-winged bird.

Ravens, carrion birds often popularly depicted as omens of death or misfortune, will be killed by baiting them with poisoned chicken eggs, shooting them and destroying a number of their eggs and nests, Idaho wildlife managers said.

Ravens are protected by federal law, and the U.S. Fish and Wildlife Service recently granted Idaho a permit to kill 4,000 ravens in four areas of the state over two years. That will begin this month and end in June, with a second round planned for next year, federal documents show.

The pilot project, developed by the state legislature, aims to protect the greater sage-grouse, a ground-dwelling bird dependent on sagebrush ecosystems in 11 Western states.

The sage-grouse's fate is at the center of a battle pitting environmentalists against industries like ranching and oil whose operations are tied to millions of acres of mostly federal lands. The Fish and Wildlife Service is to decide next year if the bird must be protected under the Endangered Species Act.

Core sage-grouse states like Idaho and Nevada have scrambled to craft plans to increase populations of the bird so it won't be added to the threatened and endangered species list. Nevada has already killed thousands of ravens in recent years.

Listing could hamper activities like the development of new oil and gas fields, wind farms, utility lines and roads. It also might result in restrictions on ranchers with permits to graze livestock on public lands where sage-grouse dwell.

Yet Idaho wildlife officials say habitat destruction and fragmentation linked to human activities are the greatest threats to the sage-grouse, with predation ranking 12 among 19 factors that contribute to the bird's decline.

Between 1.6 million and 16 million sage-grouse populated the sagebrush plains of 13 U.S. states and three Canadian provinces in the 19th century, but their populations today are estimated between 100,000 and 500,000.

Every spring, male sage-grouse, which stand two feet high, return to historic strutting grounds known as leks to perform elaborate courtship dances during which they inflate yellow air sacs on their chests to impress female onlookers.

(Editing by Stephen Powell)