A Moth Makes a Bird Walk

By David Spector Gazette Contributing Writer

What makes for a good bird walk? As someone who has both participated in and led many bird trips, I have often had occasion to consider this question. Below is one answer, in the context of a woodland bird walk that I led for the Hitchcock Center for the Environment a few years ago.

When we met I didn’t know any of the participants; they didn’t know me. We shared a common goal, a walk with views of birds, but I didn’t know how cooperative and friendly a group they would be and they didn’t know whether I was an effective leader and teacher. This walk was a success, and the key was a moth.

As we made our introductions and prepared to head into the woods, I happened to glance down and saw a moth resting on the leg of my pants. The moth was a small, non-spectacular one, one of many local species of bark-patterned moths that are difficult for the non-specialist (including me) to identify. Although I couldn’t name the moth, and although it was not a bird, I pointed it out to the group and it became the starting point of our walk.

That moth had a triangular tear in its wings, a tear the size and shape of the bill of a small insectivorous bird such as a warbler or vireo. The moth told its story as clearly as if it could talk. It had been attacked by a bird and had pulled away, leaving a bit of its wing as a low-nutrient consolation prize for the bird. Here was clear evidence that a predator lived nearby and that its attempts to take prey were not always successful.

Here, too, was direct evidence that a moth’s wings have some surface area to spare; this moth had lost a chunk of wing but still lived and flew. This individual furthermore provided indirect evidence of a deeper history and of the logic of natural selection. It is quite likely that among previous generations of the moth’s ancestors were individuals who had had similar encounters with birds; those with enough wing to spare survived to reproduce, and those that could not fly after losing a bit of wing did not. Some excess capacity, a common feature of living organisms, was favored.

My noticing the moth and showing it to the group also revealed something about my past. One of my graduate school mentors was Ted Sargent, now retired from the University of Massachusetts Amherst, who spent much of his career studying moths, their interactions with birds and the effects of those interactions on the evolution of the moths. As part of his research he tallied many injured moth wings, and used the pattern of tearing as evidence for the type of attack the moth had survived.

As a graduate student I learned much from professors like Ted. Some of that knowledge was of sophisticated mathematical methods, minute analyses of fine distinctions of natural processes and other techniques essential to an education in science. Just as important, though, was my learning to appreciate a wide variety of organisms and their interactions, to see things I would have missed, to pay attention not just to wings but to gaps in wings, and to share knowledge.

When we moved into the woods on that spring morning I was impressed with the cheerfulness of the participants, and we were treated to stunning views of many of the colorful (and some not colorful but nonetheless interesting) birds that reside in New England forests. Good company and ample birds are important ingredients for a bird walk, but it was the moth, its evidence of a bird’s bill and my sharing of knowledge learned from a friend that set the morning’s mood.

David Spector is a former board president of the Hitchcock Center for the Environment and teaches biology at Central Connecticut State University.

Earth Matters, written by staff and associates of the Hitchcock Center for the Environment at 525 South Pleasant St., Amherst, appears every other week. For more information, call 413-256-6006, or write to us.

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