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Wednesday, 31 March 2010 15:01

The Naturalist's Corner

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Pug catcher

Early last week, we were inundated with small gray moths. You couldn’t open a door without two or three coming inside. Moths inside are cool for Izzy, Maddy and the cat — all like to play with them.

One evening, at dusk, Maddy took her bug cage and went out on the deck. In about 10 minutes she was back with a cage full of moths. My curiosity piqued, I went downstairs to Google “little gray moth” to see if I could put a name with the fuzzy little face.

Next I heard a grownup “Wow” coming from upstairs. My wife appeared at the bottom of the stairs. “I just saw a little gray bird fly or jump from the dogwood tree to one of the big trees and back,” she said.

I went upstairs to look and there, perched on the dogwood, was an eastern screech owl. Sitting on a bare dogwood limb framed by the dim twilight, the owl looked elfin. It soon launched itself to the side of a large locust, then back to the dogwood; then to a grapevine and back to the dogwood. After a couple more of these sorties, I realized the owl was feeding on the moths.

We called the kids in and for 15 or 20 minutes Izzy, Maddy, Mom and I watched as the little owl tracked moths, then launched itself to tree, or branch, or grapevine in pursuit of the tiny morsel and then returned fly-catcher-like to its perch on the dogwood. While the owl appeared gray in the dusk, a look through binoculars revealed that it was a red-phase bird.

Now there were two mysteries. What was this little moth engulfing our home and enticing screech owls and how common was this fly-catching behavior? I quickly realized I was in over my antennae trying to Google this moth. Do you have any idea how many different little gray moths there are in the world? So I decided to rely on the “old-fashioned” way of seeking information — I asked someone smarter than me.

Paul Super, science coordinator at the Great Smoky Mountains National Park’s Appalachian Highlands Learning Center at Purchase Knob, identified the moth as Eupithecia sp. — common name pug. He noted that it is very difficult to separate the different species of pugs. Super said there were at least a dozen species of pugs in the Great Smoky Mountains National Park and the most prevalent by far was the common pug, E. miserulata.

This tiny gray moth has a wingspan of less than an inch. The grayish wings have small disc-like black dots. The common pug ranges from Florida to Nova Scotia and west to Texas. There is also a western population in California and Washington. It overwinters as a pupa, probably accounting for its early spring flight.

As for screech owls catching bugs, it seems insects are a large part of this little character’s diet. During a 1927 study in Nebraska, eight screech owls were dissected. Those stomachs contained 210 locusts, 2,757 other insects, 2 mice and 1 bird.

Renowned ornithologist George M. Sutton wrote about his encounter with a fly-catching screech owl. “At first we were somewhat mystified by her actions. Soon we made out, however, that she was capturing insects, which were flying about the peripheral twigs of the tree. Some of these she evidently snatched from the twigs or leaves with her feet; others she caught in mid-air, with her beak. Since I had never known Screech Owls to capture prey thus I changed my position so as to be able to see the bird more clearly. From my new station under the elm tree I saw the bird catch thus, Flycatcher-wise, at least twenty insects, most, if not all of them, the large beetles locally called June bugs or May beetles.”

All anyone has to do to learn something new in nature is pay attention.

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