— I’d been wondering the same thing for years, and now I was reading about it on the internet: a person’s take on why black-capped chickadees are occasionally seen shredding cattail fuzz during late winter and spring.

The writer said that he had come to the conclusion that what appeared to be an obvious motive was incorrect. He, and many others, had previously assumed the birds were gathering soft cattail fuzz to line their nests. Over several decades, and on many occasions, I had seen chickadees tear into cattails, fuzz flying in the wind. Usually I was in cattail marshes to photograph ducks or other wetland birds. But I never did see a chickadee carry away any of the fuzz, so I had concluded that there must another reason for the fuss over the fuzz. The question had remained for years.

The writer on the internet thought the chickadees were actually eating the tiny seeds buried in the cattail fuzz. But that didn’t make sense to me. The seeds are so small I wondered if they would provide even a tiny bit of nutrition to a chickadee, a bird that lives a hyperactive life requiring a lot of food quickly to keep the internal furnace lit.

On a sunny late afternoon a few weeks ago, I sat quietly in a duck blind on the edge of a marsh concealed in a tent-like hideout, hoping to photograph waterfowl. The ducks weren’t cooperating, so I bided the time observing a pair of chickadees through my telephoto lens. I watched the chickadees for maybe 10 minutes going about their task, probing the fuzzy head of a cattail before flying to the next one.

I watched the birds closely. It surely wasn’t evident to me whether they were eating seeds amid the cattails. Forever curious about nature, I decided to leave my blind and wade into the marsh, with camera, lens, and tripod thrown over my right shoulder. (I was wearing chest waders so the belly-deep water was not a problem.)

Carefully I crept within camera range. The chickadees were well aware of my presence — the tiny birds are notably tolerant of humans. When I was finally close enough for photos I set up the tripod and placed it in the weedy marsh, forcing the legs into the muddy bottom to provide a steady support for my camera and lens.

The chickadee pair paid scant attention to me. For a few minutes I shot photos of the birds as they went about their business, tearing into the fluff. Not once did it appear to me the chickadees were eating the seeds or anything else.

Only later upon closer inspection at my home computer did I discover what the chickadees were doing. In two of the photos, a chickadee had a small insect larva of some type in its beak.

I googled “larva in cattails” and after researching numerous sites, I surmised the larva was that of an insect called the shy cosmet moth. Now the chickadees’ habit of shredding the cattails made sense. However, I’m not a bug guy, so I e-mailed one of the images to Robert Dana, Minnesota Department of Natural Resources insect entomologist with Minnesota Biological Survey Office. He called me with his findings.

“I’m almost certain that’s the larva of the shy cosmet moth,” said Dana. “The feeding larva causes some cattail fuzz to protrude, or fluff up.” Other bug experts whom I had contacted agreed with Dana’s conclusion. Ultimately, the surviving larvae will hatch into the adult stage, a small discrete moth — the shy cosmet moth — usually in June.

So, there we have it. Mystery solved.

I must admit I feel a bit humbled, dimwitted maybe, to finally find the answer to something I had pondered for so long.

Isn’t nature grand?

Bill Marchel is an outdoors writer and photographer. He lives near Brainerd. Reach him at bill@billmarchel.com.