RAVENS IN CROSS-HAIRS? BIRDS MAY BE TARGETED IN MOVE TO PROTECT DESERT TORTOISES.

Byline: Jim Skeen Staff Writer

CALIFORNIA CITY - With ravens flocking to the desert in search of the food, water, nesting sites and other attractions provided by man, wildlife officials are considering poisoning or shooting the big black birds to help keep them from eating rare tortoises.

Ten times as prevalent as 25 years ago in the California desert - where they are immigrants, just like the growing human population - ravens are believed to be one reason for the rapid decline of desert tortoises, whose soft-shelled young they eat.

``The desert tortoise population is declining because of a number of threats. One of those is raven predation,'' said U.S. Fish and Wildlife Service biologist Ray Bransfield. ``We have found 100 to 200 shells underneath raven nests.''

Killing ravens to protect tortoises has been proposed before, and ran into controversy. In the late 1980s, the U.S. Bureau of Land Management proposed shooting 1,500 ravens in tortoise preserves near California City and near Twentynine Palms.

The idea triggered a lawsuit by the U.S. Humane Society, worried that ravens that hadn't preyed on tortoises would be killed.

In an out-of-court settlement, the BLM agreed to limit its plan to killing fewer than 60 of the birds. In the early 1990s, ravens were shot that were ``found in close association'' with three or more shells of dead juvenile tortoises.

Now, in an effort being led by the U.S. Fish and Wildlife Service, government agencies are starting an environmental assessment looking again at how to stop ravens from preying on young tortoises. The effort is focused on wildlife management areas and critical habitats such as the tortoise preserves.

Efforts will likely include a broad range of actions not limited to poisoning and shooting, officials say. Those means could include changing practices at landfills to reduce food that ravens scavenge there, trying to pick up road-kill carcasses that ravens also eat, and modifying potential man-made nesting sites, such as utility poles.

``We are cautiously optimistic about the plan they are working on,'' said Bette Stallman, wildlife scientist with the U.S. Humane Society. ``They are trying to reduce the artificial food sources - that's what we want them to do.''

The Humane Society has concerns, however, about the lethal means being considered. The poison being considered for use kills the birds in one to three days by causing kidney and heart failure.

``Taking one to three days to die doesn't sound humane to us,'' Stallman said.

Government officials said their killing plan aims at ravens shown to be tortoise-eaters.

``We will go after the birds we know are eating tortoises,'' Bransfield said. ``We will take out birds with three or more shells under the nests. We aren't just going to shoot any black bird.''

Controlling man-made raven attractions, such as road kill and water sources, is going to be much tougher. Public education should be a component, Bransfield said.

``In Ventura, we have signs that say all drains lead to the ocean,'' Bransfield said. ``Maybe we should have signs that say everything goes into a raven's mouth.''

The desert tortoises - of the species Gopherus agassizii - were labeled endangered by the federal government under an emergency designation in 1989. The permanent designation was changed the next year to threatened, which means a species is not in imminent danger of extinction but is likely to become so in the foreseeable future.

Tortoises can live well over 50 years and do not begin having young until ages 14 to 20. That complicates recovery efforts, on which the federal government has spent more than $100 million since 1990, because it takes decades to produce a new generation.

Scientists don't know how many desert tortoises remain in the wild. But they say counts in many areas show tortoise populations are barely 10 percent of what they were even two decades ago.

Scientists also don't know how many ravens live in the desert. Surveys in breeding areas count ten times as many as in the 1970s.

By itself, reducing raven predation will not keep desert tortoise numbers from dwindling, officials say. There are many other factors, including habitat loss, affecting their numbers.

``There are a whole host of threats that are working the tortoise,'' Bransfield said. ``We won't recover this species until we deal with all the threats.''

Daniel Patterson, a desert ecologist with the Center for Biological Diversity, said the desert tortoise's decline requires a holistic approach, and not just a focus on ravens.

``We have a concern that ravens will be scapegoats of the desert tortoise,'' said Patterson, whose organization has sued government agencies over its management of wildlife. ``Habitat loss, off-road vehicles, livestock grazing are much bigger issues.''

Those larger issues were addressed in the desert tortoise recovery plan issued in 1994, a joint effort of the U.S. Fish and Wildlife Service and a host of tortoise biologists.

``We have a good plan, but it's not being implemented,'' Patterson said.

The latest environmental assessment is being conducted in cooperation with the Desert Managers Group, which includes the National Park Service, the Bureau of Land Management, Edwards Air Force Base, the Marine Corps bases at Barstow and Twentynine Palms, the Naval Air Weapons Station, China Lake and the National Training Center at Fort Irwin.

A draft of the environmental assessment, with a preferred alternative, should be released this fall. Officials are hoping to have a plan in place in spring, said Amy Fesnock, a Fish and Wildlife biologist.

Jim Skeen, [phone]

james.skeen(at)dailynews.com

CAPTION(S):

3 photos

Photo:

(1 -- color -- ran in AV edition only) A flock of ravens hangs out on an irrigation pipe in Lancaster. Some birds were killed in the early 1990s to protect tortoises.

Jeff Goldwater/Staff Photographer

(2 -- color -- ran in AV edition only) The rare desert tortoise is at particular risk from big hungry birds when it is young and its shell is still soft.

(3 -- ran in Valley edition only) Discovery of tortoise shells under a nest can indicate a particular raven has been killing and eating desert tortoises.