COLEHARBOR (AP) - Experimental bird diverters installed on sections of power lines appear to be reducing the number of birds killed by crashing into the wires.

Three different types of experimental diverters were installed in April along the 3-mile stretch of power lines along the Snake Creek Embankment between Lake Audubon and Lake Sakakawea.

"In 2006, we picked up a total of 429 birds," said Craig Hultberg of the Audubon National Wildlife Refuge near Coleharbor. "That represented 67 different species. In 2007, we were down to 344 birds and 57 species."

The first half of the study was finished in October, said Misti Schriner, the study leader for the Western Area Power Administration headquartered in Lakewood, Colo.

"The Snake Creek Embankment study is the only study being done in these conditions in the Central Flyway," she said.

Similar studies will get under way next summer in Kansas and Nebraska. Schriner said North Dakota's study is particularly important because of the dramatic seasonal changes and the study area between two large bodies of water.

Not all the sections of power lines crossing the embankment were fitted with diverters. Still, the number of dead birds collected this past summer from the under the power lines was fewer than in 2006 when no diverters were in place.

While the numbers are encouraging, Schriner and Hultberg say there are many variables - such as water levels, the migration and weather - that may affect the totals.

"It does kind of narrow things down, though," Hultberg said. "If none of the diverters really work, that's information, too. This year, our observers did find that more birds were going over the wire this year than in 2006."

None of the three types of diverters - known as Swan, Birdmark and Firefly - proved 100 percent effective. Dead birds were recovered under all sections of the Snake Creek Embankment power lines. Part of the study included the testing of the durability of the various diverters, another variable that will be factored into the final analysis.

"Our Firefly devices had a 30 to 40 percent failure rate. They weren't staying attached," Schriner said. "They kept flying off the line. That makes it hard to determine their effectiveness."

The "Fireflys" are small, rectangular diverters mounted on a swivel that rotate in the slightest wind. The rotation is thought to help bring birds' attention to the green and yellow reflective surface of the diverters so that they will avoid them and not strike the power line.

"I think we have learned a lot," said Hultberg. "It's just amazing, in three miles of line, how many birds are hit that we know of and it's hard to say how many more we are missing. The big learning curve is finding the right diverter. We'll get some statistical significance over time to find out which diverters will work."

The final year of the three-year study at Snake Creek will resume in April with new bird diverters.