Otto: Turkey vultures are big, creepy and wonderful

Turkey vultures are the sort of birds that command attention.

For one, they're vultures – dark-feathered and hunchbacked. They look vaguely creepy even under the best of circumstances. For another, they're big – their 6-foot wingspan rivals that of the bald eagle and makes them hard to miss as they soar overhead in search of carrion, the dead stuff that makes up the bulk of their diet.

Now, imagine seeing not just a few of these large, eerie, roadkill-feasting creatures but rather several dozen, circling overhead like many flying monkeys. That's exactly what happened to me Saturday as I drove north on Route 47 through Yorkville.

I had just left the taxidermist's, having picked up an assortment of critters we'd had mounted for display. (Two of the three actually had been roadkill. So basically I was driving around items that would have been turkey vulture vittles, had we not intervened.)

Approaching the bridge over the Fox River, I noticed a few dark forms up ahead, high in the sky. Those few became several, and the several soon became many. That's when I knew I had to pull over and appreciate of one of fall's lesser-celebrated treats – turkey vulture migration.

When you think of migrating birds, certain images tend to come to mind. Tiny warblers, for example, flitting between branches as they glean insects that will fuel their journey south. Turkey vultures, by contrast, couldn't flit if their lives depended on it. Their bulky bodies, adapted for tugging open carcasses, are better suited to soaring, which they do with grace and apparent ease.

Flying V's are another common migration image – large flocks of noisy Canada geese flying in V formation. Or even larger, noisier V's of sandhill cranes. Yet neither of these sights, nor sounds, is apparent with vultures.

Although they move in groups, turkey vultures don't use the economy of energy created by flying in a V-shaped flock. Instead, individual birds form their own Vs as their wings swoop upward and remain, outstretched in a dihedral or V shape. They can hold this position for hours as they soar, flapping only when it's time to change direction or come in for a landing.

The secret to the turkey vulture's seemingly effortless flight lies in its deft use of rising warm air currents known as thermals. Unlike some birds that hit the air with or before the sun, turkey vultures typically wait to fly until the day is well under way.

As the sun's warming rays heat the air, thermals begin to rise. It's then, amid much flapping and flailing, that the turkey vultures take off. Circling and tilting slightly to use the currents to their best advantage, they go up with the rising air. Upon reaching the top of a thermal, they glide – as fast as 60 mph – on a downward slant until they reach the next thermal, and the cycle begins again. Mile after mile they travel in this fashion, coming down to land only as the sun is setting and the air begins to cool.

As I watched the vultures end their day, I wondered what the next leg of their journey would bring. How many miles would they go? Where would they end up?

As it turns out, only recently have scientists begun looking at the migration habits of turkey vultures – the New World's most abundant scavenging bird of prey. About eight years ago researchers affiliated with Hawk Mountain Sanctuary in Kempton, Pa., began tagging the birds in an attempt to learn more about their habits and patterns. To date more than 100 turkey vultures in the United States and Canada, as well as Venezuela – the country to which some northern birds migrate – have been marked with either red, blue or green wing tags.

Although it's unlikely any of you would encounter a tagged vulture in northern Illinois, it never hurts to look. And if you have travel plans that will take you west to the central migration flyway or east to Pennsylvania, keep your eyes open ... especially if you find yourself driving in a vehicle with former, or future, vulture vittles.

• Pam Otto, who really only occasionally drives around with dead stuff, is the manager of nature programs and interpretive services for the St. Charles Park District. She can be reached at 630-513-4346 or potto@stcparks.org.