Some birds cough up pellets of indigestible food

To fully appreciate this column you'll have to find a freshly fed chicken and, with a firm grip, hold its stomach to your ear.

What you will hear, I've just read, is the sound of the chicken's gizzard grinding away. It's a grating noise, I assume, never having done this myself.

The gizzard — which is the stomach in all birds — has a rough, sandpaper-like inner surface that reduces food items to digestible mush. Bits of grit and gravel are ingested to boost the grinding, and the pebbles are manipulated by contraction of stomach muscles. It seems to be a noisy process.

Bird digestion is more interesting than you might think. I learned this while searching the Web for information about pellets, which are little bundles of animal parts that can't be digested by a bird. The stomach — and it appears that birds have stomachs much superior to ours — takes bones and fur or fish scales, and forms a mass that the bird then hacks up.

Owl pellets are the best known. The pellets can be disassembled for close study. There are bones in there, and teeth, all wrapped in fur that has seen better days. Fur forms the casing of the pellet. It covers sharp bone ends, easing passage of the pellet as it's coughed up and out the throat.

If you know your mammal bones, it's sometimes possible to identify the meal by species.

I presently have a cigar box full of pellets, a wealth of these hard-to-find items. My grandson and I found them this summer beneath the roost of a pair of great horned owls. It was a wow moment. Pellets are ejected about six hours after eating. (Find a roost, maybe find a pellet.)

There must be 30 pellets in the box. And one moth ball to discourage whatever. Pellets can be a big hit in elementary-school classrooms. (Pellet excitement generally exists in inverse relation to age. I'm an exception.)

Bird digestion is tough business, often involving strong digestive acids that kill much of the peripheral stomach life-forms. Vultures are a good example. Their job is to eat dead, often really foul stuff. Their stomach fluids include hydrochloric acid, quite enough to kill botulism toxin and anthrax bacteria or whatever flavors rotting meat.

Owl pellets for disassembly are best sterilized by spending 30 minutes in an oven set at 250 degrees. The pellets first should be wrapped in aluminum foil. Inform your spouse.

Owls are not the only bird species to produce pellets. Last summer I found a gull pellet on a rock shelf along the Lake Superior shore. Its wrap held bits of mussel shell, fish bones and fins, and what looked like fur. If I saved it, I've misplaced it. Too bad. It would be interesting to open. Gulls have a broadly based palate.

Other species known to wrap indigestables and spit them up include grouse, nighthawks, swifts, kingfishers, shrikes and even some thrushes (beetle shells perhaps?).

Truly, though, holding a chicken to your ear sounds like something done by beer-stained men in one of those dumb-stunt movies. Should you try this I'm certainly not assuring that you will emerge with either profile or reputation intact. However, if I ever get that close to a chicken …

Lifelong birder Jim Williams can be reached at woodduck38@gmail.com. Join his conversation about birds at www.startribune.com/wingnut.