Oregon Public Broadcasting

As winter continues in the Northwest, so does an ornithological mystery.  People seldom see barn owls on the wing.   
But these ghostly white raptors die in large numbers on the region's highways every winter. 

No one knows why.  But scientists are trying to find out.  Correspondent Guy Hand joins Idaho researchers as they scan the roads for dead barn owls -- and answers.

Than Boves: "Alright.  So immediately when you look at this bird you can see it's got a broken wing, possibly a broken neck.  So it probably got clipped by a semi, got knocked to the side of the road and then died.

Than Boves with dead barn owl

Than Boves, graduate student at Boise State University, has gotten really good at spotting dead barn owls.  After all, he spent two years prowling a hundred mile stretch of Interstate 84 through the southern Idaho desert—often driving 20 miles below the speed limit -- scanning the shoulder for road kill.

Than Boves: "As you can see it's been pretty much smashed to nothing . . . So I'm just going to take this one and throw it out into the field."

He tosses the flat disk of feathers, frisbee-like, into the dry grass.  It's too far gone for study.

Than Boves: "We've seen 4 barn owls now."

That's four in close to a half hour.  I ask him how many he's found  in a day.

Than Boves: "Yes, my record is a hundred and four barn owls in one day. . . The last 30 miles were done in the dark . . . and by the end my eyes were sore, my head was hurting."

The owls deaths are especially striking if you look at the researcher's entire study period.

Than Boves: "We came up with a range of between 1400 and about 3000 birds over two years."

Boves has found all kinds of dead animals -- even a peacock -- on this 100 mile stretch of treeless highway.  But wild or domestic, barn owls out number them all.

Than Boves: "We've found three or four times more dead barn owls than squirrels than skunks than raccoons than cats than dogs.  They are the most commonly killed animal along the highway . . . So I think  that's just unbelievable. . . . And the fact that I've only seen two or three live ones ever in my life and now I'm finding thousands and thousands of dead ones."

Barn owls range over nearly the entire U.S., including Oregon and Washington.  But Jim Belthoff, Boves's biology professor and fellow researcher, knows of only one other state that has looked at barn owl highway mortality: California.   He says neither study has answered the question of why these elusive, nocturnal hunters are killed on  
roadways in such large numbers.

Jim Belthoff: "There's something about barn owls that make them unique in this regard or much more likely to be hit by the traffic.  And it doesn't matter whether it's an interstate highway or a two lane road where the speed limit might be 55 miles an hour."

It's likely that barn owls are being attracted to an abundance of rodents on or near the highway.

Jim Belthoff: "But there are lots raptors being attracted to these areas   . . .  and we're not finding them dead in anywhere near the numbers we're finding barn owls."

Dead barn owl on Interstate 84 near Boise

Of all the dead Idaho raptors—hawks, falcons, and owls—90% were barn owls.  But why?  There are plenty of possibilities: that changes in headlight technology or the sounds of traffic confuse the owls, that vortices whipped up by 18-wheelers suck them under, or that  pesticides slow their responses.  Solid answers will have to wait for another study.

Than Boves: "This is a nice spot right here.  So you want to set up the box so the hole is kind of facing  
the northeast."

To help with further research, Than Boves and his crew are setting up a series of large nest boxes.  Those boxes will give barn owls roosting sites away from highways and give future researchers convenient locations to study the birds more closely.

Than Boves: "I've spent so much time with dead ones that I'm actually really looking forward to once we get these barn owl boxes up to coming back and getting to work with some of the live ones."

The next research step will be to look at the owls that nest in those boxes, to study their behavior, to hopefully find out why these ghostly-white creatures are such common roadkill.

Online:

Barn Owl Natural History

Article on Idaho Barn Owl Deaths

British Barn Owl Deaths