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Counting owls in the dark

March 25, 2010

At last we had two calm nights in a row, so I’ve done my two owl surveys for the year.  I organize the British Columbia-Yukon Owl Survey, so it would have been bad form if I didn’t get my routes done and all the other volunteers did.  Together, we cover almost 100 routes every spring, each of us driving forest roads in the night, stopping at preset points, listening for 2 minutes, and moving on.  My routes go through the White Lake basin southwest of Penticton and along the KVR trail north of Naramata, BC.

Northern Saw-whet Owl female looking out of nest hole in cottonwood, Naramata 2007

Why count owls?  Well, their populations are a good indicator of the health of forest ecosystems, but they aren’t found regularly on other broadscale surveys such as the Breeding Bird Survey and Christmas Bird Count.  The BC-Yukon owl survey has been going for 11 years now, and we’ve built up quite a database on the distribution and abundance of owls, though it’s a bit early to detect any population trends.  We’ve certainly noticed that it’s been hard to find Western Screech-Owls on the coast lately, but that’s a topic for another blog.

Two nights ago I drove the White Lake route under a bright half-moon.  The first part of the survey was quiet, but I finally heard a Northern Saw-whet Owl tooting away at Mahoney Lake, and then another squawking along the shores of Skaha Lake south of Kaleden.  I’ve had Great Horned, Long-eared and Western Screech owls along this route in the past, so it wasn’t a very diverse result; perhaps it would have been better had I done it earlier in March.  Last night, my son Russell and I drove the KVR trail north of Naramata under similar conditions with more heartening results.  In only 10 stops we heard 3 Great Horned and 3 Northern Saw-whet Owls, I think the best result ever for that route.

An unexpected bonus was a brief sighting of a weasel dashing across the track, still in its white winter coat.  The nicest surprise came after the survey, though.  We stopped along North Naramata Road where Naramata Conservation had put up some nest-boxes 2 years ago.  We scratched on the first tree with a box and a male flicker poked his head out–we’d obviously disturbed his sleep.  As we approached the second box, Russ saw an owl fly away from it.  We couldn’t see where the owl had gone so Russ climbed to the box and carefully opened the side and found 7 eggs inside.  Almost surely a Northern Saw-whet Owl, then, since screech-owls wouldn’t have that large a clutch.  We’ll have to go back and check during daylight to make sure!

(PS:  Russ did go back to check the box–it was a saw-whet–you can read about it and see a photo on his blog).

Small owls readily take to nest boxes, especially in areas that lack natural snags with big woodpecker holes.  Here are front and side illustrations of the boxes I use (make sure you throw a couple of handfuls of sawdust or wood chips in the box when you put them up–owls never add any nest material of their own!).  Click on the plans to see a larger image.

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