Monday, February 6, 2017

What made these mysterious holes in clay bank?

Something has enlarged some of what appear to be kingfisher nesting holes
I checked out these holes in a clay bank on an island in front of Golden Arm last summer after several of our anglers reported seeing them.
I can explain the smaller holes. Kingfishers nest in clay banks and make holes just like these. So do bank swallows but they are rarer in these parts than are kingfishers.
But what about the larger ones?
My guess is that creatures have enlarged a couple of the kingfisher holes to make their own dens or nests but I'm at a loss for what those creatures were.
There are no trails from the holes down to the water so it would seem the creature and its young didn't travel that way. Neither are there trails going upwards. This would seem to rule out animals like otters, muskrats, etc.
The size of the hole is probably a clue. The holes are big enough for a woodchuck, also known as a groundhog, but it would be silly for such an animal to make a hole entrance on a vertical bank face, 15 feet above the lake. Also this island was too small to provide enough food for a woodchuck.
My best guess is that the holes might be nesting sites for merganser ducks. They are cavity nesters and mostly nest in pileated woodpecker holes in large trees; however, I have also seen them use abandoned woodchuck holes in the ground. Since these holes couldn't have been made by a woodchuck I'm surmising that maybe the ducks enlarged the kingfisher holes. I've never heard of such a thing though.
Does anybody know what actually went on here? Any ideas?
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regor draagyn said...


Dan Baughman said...

Yes we do have wood ducks. They are uncommon though. You've seen wood ducks use holes in banks like this before?

Doug Billings said...

Would winter snow depth have any influence on what might utilize an existing hole during the long cold winter months? What appears to be fifteen to twenty feet up in the summer might be closer to ground level in the snow. Just a thought...

Dan Baughman said...

This is like the case of the giant beaver. There used to be a beaver stump on Rowan Lake, a small lake between Golden Arm and Pipestone Bay, that must have been 12 feet off the ground. It seemed impossible that a beaver could have cut down this tree. However, the tree was growing about four feet from the edge of a small cliff and the beaver stump was about level with the top of the cliff. The only explanation was that snow had drifted beyond the edge of the cliff and a beaver had somehow gone out on the drift and cut down the tree. How a beaver could be above the ice at a time when there would have been a snowdrift with a crust on it is another mystery.