Burrowing owls flew almost 2,000 miles, study finds
By Brett French
Just like retirees traveling south to escape the snowy winter, two female burrowing owls have been documented traveling almost 2,000 miles to central Mexico from Eastern Montana for the first time.
“Now we’re learning more about how incredible these birds are,” said David Johnson, of the Global Owl Project.
Last year, GLOW fitted 30 burrowing owls in the Northwest and Canada — including three from the Charles M. Russell National Wildlife Refuge in Montana — with tiny backpacks containing satellite transmitters. The devices track their migration routes and destinations in an attempt to give researchers insight into the birds’ population decline.
No one has completed a survey to arrive at a population number for the birds in Montana, according to Steve Huffman, executive director of Montana Audubon. “If you polled a bunch of owl experts, though, you’d probably find the range of the species is declining and Montana is no exception to that,” he said.
In Canada the bird is listed as an endangered species because of “habitat loss and fragmentation, road kills, pesticides, food shortage, fewer burrow providers and mortality on migration and wintering areas,” according to Parks Canada.
Montana Fish, Wildlife and Parks lists the bird as “potentially at risk because of limited and/or declining numbers, range and/or habitat, even though it may be abundant in some areas.” The Forest Service and BLM consider the owl a sensitive species.
With its burrowing owl migration study, Johnson said GLOW is hoping to keep the birds off the endangered species list in the United States by developing conservation strategies.
Burrowing owls date back in the fossil record millions of years, Johnson said. They may be one of the very few birds to nest underground, an adaptation to their prairie home where few trees exist.
Instead, the birds use abandoned badger, swift fox and prairie dog dens to nest in, often as far as 10 feet underground to escape the reach of predators like coyotes.
The owls are small, averaging about 9.5 inches long with 21-inch wingspans and tipping the scales at only 5 ounces. In addition to bugs, the owls will eat small mammals like mice and voles, birds, reptiles and snakes.
Most of the owls live about five to six years. The females migrate south around October to stay healthy for the spring breeding season when they return north. The exception is California’s burrowing owls, which reside there year-round.
“One of the things I’ve learned is how incredibly tough these birds are,” Johnson said.
When initially fitted with transmitters, the antenna was made of 70-pound test fishing line. The birds chewed through that, so Teflon tubing was substituted for the line. The satellite transmitters are expensive, costing $3,500 apiece, but they provide a clearer picture of the birds’ migration.
Every 48 hours the solar-charged devices turn on for 10 hours and send a signal every minute before going silent for another 48 hours. From these transmissions, Johnson has learned that the birds travel about 100 to 200 miles in a night, averaging 30 mph.
“When they migrate it seems to be pretty darn direct,” he said. “They don’t waste time.”
CMR biologist Randy Matchett watched the migration data pop up on his computer screen, impressing him with the birds’ speed and ability to fly high. Although the transmitters don’t contain an altimeter, it was evident by their route that the owls were flying over 10,000-foot peaks, he said.
“Everyone knows birds migrate long distances, but it is kind of neat to watch it alive in real time,” Matchett said.
Johnson said one of the surprises GLOW discovered when tagging some burrowing owls in Oregon was that a male flew north, rather than south, for the winter.
“The male’s goal was to go someplace to tough it out and get the best burrow” for the following spring’s mating season, Johnson said. “As the males get older, they get tougher.”
The satellite transmitters are a big step up from the old technology. As far back as 1912, ornithologists captured and placed numbered bands on birds to try to track them. Trouble is, the bands could only be recovered if the bird was recaptured or found dead, and they were no help in identifying migration routes.
Bands were more recently replaced by tiny light-sensitive monitors that could track the duration of sunlight hitting them, giving researchers an indication of where the birds had gone based on the length of days at different latitudes. The transmitters are relatively inexpensive — about $200 — compared to satellite trackers, but again they gave only a vague indication of migration routes and the birds had to be recaptured to recover the data.
The more expensive satellite transmitters – which weigh in at 6 grams compared to 3.2 grams for the ambient light geolocators – track the birds’ location within 150 meters, the battery’s voltage and the temperature. The units also have small solar cells to recharge the battery.
“It’s amazing it works at all, actually,” Johnson said.
The Montana owls migrated south by traveling east of the Rocky Mountains to north of Mexico City. One has settled northeast of Guadalajara and the other is in the state of Durango. The third Montana owl was found dead before it left, possibly dinner for a predator.
Off the 22 GLOW-tagged owls that started their migration in October, 17 are now in Mexico. By March or April, the urge to fly north should send them migrating again.
“Now we’ll wait to see how they come back,” Johnson said.
Showing just how amazing the birds are, in 2013 a burrowing owl captured near Baker, Ore., came back to the exact same burrow after wintering south of San Francisco.
As a follow-up to the satellite transmissions, Johnson said GLOW will be examining the habitat conditions where the owls are wintering.
The study of owls has been a personal mission for the 58-year-old Johnson since a screech owl landed on his tent when he was an 11-year-old boy in Minnesota.
“It called for 20 minutes. Ever since then I’ve seen owls as close friends,” he said. “So I say I didn’t pick owls, they picked me.”
Since 1976 he’s been working on owl projects full time.
“I’m going to work on conservation of owls till my last breath,” he said. “Because the more I’ve studied and observed them, the more impassioned I’ve become.”