http://www.adn.com/news/alaska/anchorage/story/9381515p-9294895c.html As Bob Tierney patrols the Anchorage landfill, he's scanning the mountains of dirt and refuse for intruders. Forget the trespass notice. When he sees an interloper, Tierney opens fire. He takes his job seriously, and to get it done he uses a $10,000, custom-built, .20-caliber rifle that he says is dead-on for at least 600 yards. Those beady-eyed ravens and gulls don't stick around long. "This is kind of my own private rifle range," says Tierney, who mostly shoots to scare, not kill. Tierney, 77, works for the U.S. Department of Agriculture's Wildlife Services program, which is contracted out by the landfill to rid the area of pests, like birds. Uncontrolled, the birds -- especially the ravens, which peck and pick at whatever they can get into -- might puncture the landfill's thick, high-density polyethylene liner, allowing disease and contamination to filter into groundwater, disposal foreman Rick Nissen said. Big flocks of birds also pose a threat to aircraft operating from a field at nearby Fort Richardson. When the landfill was built in the 1980s, city officials agreed to keep their numbers down. They get used to the 'bird bangers,' but they can't get used to the sonic crack of my rifle," Tierney says. The 15-mm bird bangers are similar to an M-80 firecracker but are propelled through the air by a small handgun, like a flare. But the bangers can reach only several dozen yards, and using them requires Tierney to rove the dump's roughly 85 actively used acres extensively. There are up to eight other people combatting the birds, depending on the season, and most of them use a shotgun for their longer-range work. Tierney wouldn't lower himself to such a brute weapon. He prefers to deliberately, methodically scope out the birds and surgically force them out. "I can raise those birds out of there by shooting a favored rock out there," he says. "It takes nice tools to hit a rock 400 yards out there."