Wednesday, April 14, 2010

The owls of April

Northern Saw-whet Owl, Lappe, April 7, 2010. Photo courtesy Aarre Ertolahti (see story below).

Last Friday we filled our Thermoses with hot chocolate and headed out to Nocturnal Owl Survey Route # 67, along a logging access road west of Marathon. The route consists of 20 stops evenly spaced along 35 km of rough road. At each stop, we would spend five minutes listening for owls before and after we broadcast calls of Boreal and Great Gray Owls. We would then record the number, approximate distance, direction and duration of all owl species heard. This is a standardized protocol that enables researchers to monitor trends in owl populations across the country. This particular route has been monitored for about 10 years.

Martha, Nolan, Wayne and I met up in a clearing just north of the first stop. Conditions seemed ideal - only a slight breeze, a clear sky the temperature just above freezing. Wayne reported that he'd heard a Great Horned Owl minutes before and soon we heard the distinctive calls of both Boreal and Northern Saw-whet Owls. It was 9:10 pm; time to start the survey.

During our first eight stops we heard only a few nocturnal creatures. A male American Woodcock was displaying and calling overhead at Stop 3 and at several other stops we heard choruses of Spring Peepers and Wood Frogs, but no owls. It wasn't until 10:20 pm, at Stop 9, that we heard our first official owl of the night, a Northern Saw-whet, calling continually from the Jack Pine stand a few hundred metres to the NE. We would hear more owls - Great Horned, Northern Saw-whet and Boreal - at seven of the next ten stops. The tally for the night, including four owls heard outside of the listening intervals, was:
Northern Saw-whet Owl: 5
Boreal Owl: 3
Great Horned Owl: 4
Unidentified (perhaps Long-eared): 1
Of the nine owls we tallied during the actual monitoring & playback intervals, eight were detected during the first two "listening" minutes, before we broadcasted any recorded calls. In terms of relative abundance, our results closely match the totals from the 2009 monitoring season as reported in the annual newsletter (PDF):

2009 Survey totals for Northern Ontario

Northern Saw-whet7233
Boreal71 28
Great Horned2718
Great Gray2111
Northern Hawk11

We had an excellent time and we all look forward to another late night of hot chocolate and owls in April of 2011.

Here are some results from the past week for other survey routes in NW Ontario:
  • April 4: Gorham-Ware Twp (w. of Thunder Bay) - Northern Saw-whet: 5; Great Horned: 1; Barred: 2; Unidentified: 2.
  • April 11: Hwy 627-Heron Bay - Barred: 1; Northern Saw-whet: 1.
  • April 12: Hwy 11 near MacDiarmid - Northern Saw-whet: 1; Boreal: 6; Great Horned: 1.
* * * * * * * * * * *

Lappe resident Aarre Ertolahti generously shared the above photo of a Northern Saw-whet Owl. Aarre wrote:
When I was doing surveys for the Atlas of the Breeding Birds of Ontario a few years ago, I decided to check all the tree cavities around my place by tapping on the tree trunks and then checking for any activity. I found several species of nesting birds as well as a Flying Squirrel. The best find was a Saw-whet Owl occupying an old Flicker nest cavity. I saw a juvenile NSWO at the opening a couple of weeks later. Ever since then, every spring I have tapped on a few trees with large cavities made by Flickers or Pileated Woodpeckers, to see if I could find another nesting Saw-whet. Last week I found one, very close to our house, occupying a cavity that was used by Pileated Woodpeckers last summer.

Ontario Nocturnal Owl Survey (Bird Studies Canada).

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