by Genesee Keevil
It is hard to fool a flycatcher.
Tara Stehelin tried.
Last summer, hoping to lure unsuspecting males into mist nets, the Yukon behavioural ecologist created a decoy. She wanted to catch the birds to band them and outfit them with tiny backpacks.
Flycatchers are in decline. Over the past four decades, 70 per cent of olive-sided flycatchers have disappeared. Stehelin wants to figure out why, and the tiny backpacks may help her do it.
Each backpack contains a geo-locator with an electronic light-sensor that can pinpoint a bird’s location to within 100 metres, using only sunrise and sunset data.
The idea is to figure out where in South America the birds overwinter, and their migration routes, dovetailing that information with environmental hazards and regional changes.
Stehelin suspects the flycatcher crash has to do with disruptions in South America and along migration routes, including deforestation, mining processes involving mercury, and pesticide use. Climate change could be another culprit, though it’s too early to tell, she says.
To catch flycatchers, Stehelin needed a decoy. But she didn’t have a dead flycatcher to stuff, so she stuffed another bird skin instead that had similar colouring and was roughly the same size.
She set the stuffed bird behind one of her nets, hoping male flycatchers would attempt to chase off the intruder. Flycatchers are very territorial, and get aggressive.
But the flycatchers weren’t fooled by the fake.
The stuffed bird didn’t stand up to weather well either, and something eventually ripped it partially apart.
This summer, Stehelin has given up amateur taxidermy and is going high-tech.
Her new decoys are picture perfect, should withstand full-blown flycatcher fury - and are made out of paper.
She got the blueprints from bird biologists in Alaska, who sent a computer file that can be fed to a 3-D printer. Stehelin walked across the parking lot at Yukon College and into the Yukon Research Centre, with the flycatcher file to see if she could print a bird.
The Yukon Research Centre could print Stehelin a 3-D bird, but it would have been pure white. To get a full-colour flycatcher, the research centre connected Stehelin with Tom Bamford, the owner of Mid Arctic Technology Services - the man with the right machine.
Bamford has the only colour 3-D printer in the Yukon. The big orange contraption is the size of a large fridge and somewhat reminiscent of those midway machines where mechanical arms are used try to grab unsuspecting teddy bears. Only in this case, the arms whizz around with glue-coated wheels and razor sharp titanium blades.
Stehelin gave Bamford the 3-D flycatcher file. But Alaska’s digital flycatcher wasn’t in colour. So Bamford had to play around for hours with Internet images of flycatchers he drummed up, carefully laying colour over every three-dimensional angle on the computer model. Once he got the colour close, from all possible angles, Bamford sent the image to the printer.
First the machine prints all the colour bits on hundreds of sheets of paper. Each piece is then sent one-by-one up to the glass box with the whizzing arms. Glue is rolled across the image with a tiny robotic wheel, then the paper is pushed up onto a hot steel plate with a one-ton press, fusing it to all the sheets below. The final step is shredding. The blades slice, fast and furious, around the image before the next piece of paper slides onto the stack and the whole process starts over.
Eight hours later, Stehelin had her bird - a perfectly coloured, three-dimensional paper decoy that looks and feels like painted wood.
From a distance, it appears to be a brownish green bird about the size of a robin. Up close, the thin layers of paper are visible, like tiny veins running across the decoy’s body.
“These ones you can’t rip apart,” says Stehelin, who has witnessed birds shred decoys. Just to be sure, she is giving her hard-packed, varnished flycatchers one more coating of glue. She also has to jury-rig legs onto the decoys, so she can attach them to low branches, or secure them to the ground. The idea is to get them close to vegetation to help trick the flycatchers, she says.
Although the sexes look similar, Stehelin printed male decoys, in hopes of catching mostly males for the banding and backpacks.
Her plan is to work the tiny backpack straps under the feathers, so the birds won’t preen them off on their long journey south in the fall. She’s targeting males because she doesn’t want to disrupt females when they are incubating or hatching their young.
The decoys will go out mid-May, if the weather stays nice. “Then we’ll see if the new shape flies,” says Stehelin.
She hopes to outfit 10 flycatchers with geo-locators. That should be the easy part, especially with the new 3-D decoys.
The hard part will be the next summer, trying to catch the same birds - flycatchers than might now be wise to the decoys - and get the backpacks off to track the data.
“I just hope I can fool them again,” says Stehelin, with a laugh.
This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at http://www.yukoncollege.yk.ca/research/publications/ newsletters_articles