Yellowstone Reports

The Search Begins

Looking for Boreal Nests
by Dan Hartman

March 3, 2015

March 1st officially began my boreal owl study. The wind was minimal, the sky clear with an almost full moon lighting the landscape. I was expecting a good night, so was somewhat disappointed when I only heard two. The temperature hovering around zero could have been the culprit. The one positive. Both calls were from new owls. Ice Box Canyon and Upper Barronette. So I've now heard five total.

The next morning, I snowshoed into where I'd heard a possible nesting song back in mid February. Cindy dropped me off along a quiet stretch of highway and I started up slope. I had told Cindy to return in an hour thinking that would give me time to search the area. Also I had to split a lot of wood at the cabin that afternoon and didn't want to wear myself out.

Almost immediately I came across ermine tracks. And a very large ermine at that! For the next hour, his tracks were always in sight as he criss crossed the whole slope. Higher up, a marten trail. This made me feel good as marten and ermine have disappeared around our cabin, but here they were thriving.

Years ago I came up with a theory based on personal experience. My friend, Jeff, and I had come upon a saw-whet owl while hiking in the Tetons. As we were checking out the little owl, a marten suddenly appeared to climb around the saw-whet before moving on. Flash forward a few years. I was following a fresh marten trail below the cabin when it led me into a thick patch of spruce. There I found white-wash and pellets from a saw-whet owl. Birds began harrassing something fifty yards away. I snowshoed over to check it out. I found the immature saw-whet owl that had been flushed off its perch by the marten I'd been following. Then it hit me. Many times I've found mice tucked away by saw-whets at their perches. Martens smell these out and steal their caches. Thus my theory: One can find owl perches by following marten tracks as they forage through the forest.

I had to abandon that idea today however as I was to be picked up on the highway shortly. I got back to my objective. Search for possible nesting cavities.

Investigating snag after snag I finally found a few clustered all in one place. They were in the general location I'd heard the owl calling and were all on the dark side of the tree, which cavity nesting owls prefer. But were the wholes large enough? I wasn't sure. On my way back down towards the highway, I found two more cavities. One was perfectly sized, but right beside the road. I also came across two more important needs for an owl nest. Lots of mouse and vole sign and open water for bathing.

I'll keep making these forays into the forest where ever I hear owls calling. Maybe by June I'll have a nest.

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