PENDLETON -- A little owl is making a big comeback on the grounds of the Umatilla Chemical Depot.
Standing about as tall as a 20-ounce soda bottle, burrowing owls have increased their numbers by 15 times during the past four years.
In 2008, there were only three or four pairs of these owls. This year, there are 61 pairs.
"That's unique to the depot," said David Johnson, a member of the Global Owl Project and head of the burrowing owl work at Umatilla. "It's a population stronghold in Oregon."
The burrowing owls are native to the depot lands. Historically, they used hollows dug by badgers to make their homes. But in the 1980s, officials accidentally rid the area of badgers when they were trying to capture coyotes to reduce predators of antelope.
"No badgers, no holes. No holes, no nesting places for burrowing owls," Johnson said.
In 2008, hardly any owls were left. That's when the Burrow Masters got to work.
For the past two years Johnson and 25 to 35 volunteers have built new homes for owls. These homes are made of half of a 55-gallon barrel and a 10-foot long, 6-inch diameter drain tube.
Each mating pair uses two spots. A female picks one site for nesting and a male picks another for storing food. Each pair of burrows are about 15 feet apart.
"Youngsters run back and forth between them," Johnson said. "It becomes a safety thing as well. This way they're not forced into one hole."
Of the 61 pairs at the depot, about 35 percent are birds that were banded there -- meaning they're native -- and 65 percent came from somewhere else.
The depot hosts 115 burrows. This year the Burrow Masters plan to build 44 more -- enough for 22 more mating pairs.
"About 93 percent of our burrows were occupied by owls," Johnson said. "What they really needed was a nest site. They can find that at the depot and congregate there. They were just desperate for nest sites."
The few nests that weren't occupied were near a circle irrigation pivot and Johnson worried the use of pesticides had reduced the owls' available food -- insects. He said owls never used those sites and they are being moved.
Other study sites elsewhere in the U.S. have 10 percent to 15 percent occupancy, he said.
The depot is different because it holds 17,000 acres of relatively untouched land.
"There's not many places in the Pacific Northwest that offer burrowing owls a big block like that," Johnson said.
Now that there are so many owls at the depot, Johnson hopes they will reproduce and move on to other places, becoming what he calls a "source population." Even with the big jump at the depot, the burrowing owl population is still declining by about 1.5 percent each year in Oregon and Washington. Johnson isn't sure what the total population is, and he isn't sure anyone knows, because the only owls being counted are those being studied, like the depot owls.
"We're trying to help stabilize the population and bring it back to a stationary level," he said. "We're doing that in some measure on the depot."
To learn of those other places owls might go, Johnson has two ways of tracking them.
In the past he has used geolocators that measure ambient sunlight to give the owl's location. The device weighs only 3.2 grams -- a little less than a nickel -- and is strapped onto the 150-gram owl like a backpack. Geolocators gather information for about two years but researchers have to retrieve them to get the data.
In 2010 Johnson put 20 geolocators on owls and recaptured seven for data.
Three owls first went north to Washington, then south to Oregon and wintered there. One stayed in central and southern Oregon for the winter.
"One left in September and made a beeline for Vegas," Johnson said. "He spent the winter in central Nevada and came back."
On the last two the geolocators stopped working after 25 days.
In 2012 Johnson plans to use a more accurate device, a satellite tag that weighs 5 grams and is accurate to within a meter of the tag. It also straps onto the owl like a backpack.
One owl was tracked with a satellite transmitter from Alberta, Canada, to Montana to Arizona then straight to Baja California, Mexico, for the winter. Then in the spring she flew from Baja to Colorado in five days and settled there for the summer.
"That was really an eye-opener," Johnson said. "We expected them to migrate back and forth. They don't always do that. That's the benefit of having satellite tags."