Wildlife Spy: A gathering of cranes

Tip: In the fall, you can tell the difference between cranes hatched this year from adults by sight and sound.

In a last, sunny blast of summer, this wildlife spy enjoyed the spectacle of sandhill cranes at the Tanana Valley Crane Festival at Creamer’s Field State Migratory Waterfowl Refuge in Fairbanks.

 

In late August, crane families from the region, often up to several thousand birds, gather to feed in the fields for several weeks before heading south. It’s a great opportunity to observe the behavior of one of the most ancient bird species alive. Sandhill crane fossils have been found that date back at least 2.5 million years, so they’re doing something right.

The gathering at Creamer’s is the debutante ball for the young cranes hatched this year. (For some odd reason, young cranes are called “colts”.) The youngsters learned to fly mere weeks ago and most are still smaller than their parents.

A juvenile sandhill crane is easy to spot by a crane profiler: overall they are more rusty-colored than adults, especially on the head. They lack the scarlet, bare skin on the forehead of an adult. A juvenile doesn’t lose the feathers covering its entire head into the flashy adult baldness until partway through its first winter. The colts also sound different than adults. They have a high, peeping call, not nearly as loud as the adult trumpeting, because their vocal chords haven’t fully developed yet. At this time of year, you can hear the piping of the chicks in concert with the deeper adult calls.

Spending an afternoon at one of the crane-watching stations coordinated by Arctic Audubon volunteers, I watched the cranes fan out through the fields, families of three and four calling as they fed. The plants were tall enough to hide the cranes when they bent down, heads and necks occasionally popping into view.

Suddenly, a ruckus spouted from the far field. Cranes bugled with increasing volume, flocks of Canada geese adding to the din as they flew up. Quickly scanning the skies, I spotted the culprit: A bald eagle crossed the meadow with powerful wing-strokes.

A storm of hundreds of cranes and geese erupted into the air. The eagle rocketed through it, in hot pursuit of a Canada goose flying faster than I’ve ever seen a goose move. They passed behind a clump of trees, and those of us watching held our breath. The goose pelted from behind the trees, widening the gap and we all breathed a sigh of relief as it escaped. Although an eagle wouldn’t take an adult sandhill, and probably not a full-grown colt, no one took any chances. When the eagle flew off, cranes gathered close together around a pond, only slowly wandering back to feeding.

One morning as I lurked with my camera, a crane called out and jumped from the ground, stretching its neck and legs and flapping its wings once, then twice. It touched down, and another bird in the group hopped a little. The first bird leaped again, seeming to float. The other crane crouched, head low to the ground, then sprang up. The dance went on only for a minute or two, but it was thrilling to think of the eons behind the gestures.

From past intel, I knew cranes danced as part of courtship. They mate for life and renew their bond through dancing. But dancing seems to serve other purposes as well. Local crane experts Christy Yuncker-Happ and George Happ have watched a nesting pair of cranes on their property for more than a decade and created a “Sandhill Crane Display Dictionary” pocket guide (available on Amazon). They say the parents teach their colts to dance, strengthening the family bond. The bond is important, because the family remains together through the youngsters’ first migration so it can learn the route from its parents, and winter. Dancing can also express aggression or territory defense, depending on the context. It’s an ancient language, but versatile.

In Southeast Alaska, be careful of confusing sandhill cranes with another suspect, the great blue heron. Both are large birds with a long neck, long legs, and long sharp bill. The relationship, however, is only on the surface, and with a few clues, you’ll be able to spot the difference in a split second. A sandhill crane flies with neck outstretched, while a great blue heron holds its neck in a distinctive s-curve. While cranes are omnivores, feeding on grains, plants, insects, small mammals and amphibians, herons are predators. One of the vertebra in the heron’s neck is specially formed to provide that lethal s-shaped coil that allows the heron to strike prey (fish, amphibians, birds, or small mammals) with lightening speed.

Another difference is smaller. Cranes can’t perch: the back toe on each foot is small and useless, barely reaching the ground. Herons, on the other, well, foot, often roost in trees and nest in colonies in trees.

You have to listen for the last major difference. Great blue herons give a loud, raspy croak. Sandhill cranes give a trilling bugle, which you can hear from surprisingly far away. Part of the reason for the volume is because a crane’s trachea (windpipe) is coiled up within its chest, almost doubling the length.

Cranes tend to use the same migration staging and stopover places. At the festival, I was thrilled to spot a crane with a yellow leg band clearly enough to decipher the numbers and letters. Several studies of crane migration have banded cranes over the years. The crane viewing station had a reference book of the numbers. The crane I spotted had been banded at Creamer’s in 2007.

Don’t look for cranes banded at Creamer’s Field in Southeast though. Alaska cranes use two different flyways, or migration routes, and ne’er the twain shall meet. The Arctic and Interior-nesting birds, including the ones at the festival, use the Central Flyway, winging their way down through Saskatchewan to winter in Texas. Cranes from Bristol Bay and Southcentral Alaska head down the Pacific Flyway, following the coast down through Southeast until they reach the Stikine River Delta.

Cranes need to stop and refuel along their migration routes. A 2005 study by Michael Pertula and Thomas Rothe, of the Alaska Department of Fish and Game, used sattelite tags to follow crane migration from Bristol Bay and Cook Inlet. They found four major stopovers where cranes stayed for more than a day: Yakutat Forelands, Copper River Delta, Gustavus Forelands (which includes Dude Creek State Critical Habitat Area), and Stikine River Delta. Gustavus is one of the longest stops, with birds staying up to a week. Pertula and Rothe mention a study that counted more than 12,000 cranes stopping in Gustavus, nearly half at Dude Creek!

There remains a bit of a mystery about the cranes that nest in Southeast: what route do they use? In the 2005 study, the Southcentral birds all moved to an inland route after the Stikine River. Other studies mention some cranes stay along the coast after the Stikine stop. Why would there be such a fork in the road?

One possibility is there may be a different subspecies of crane in Southeast. There are several subspecies of sandhill cranes. Smaller birds need less fuel to fly farther. The birds that winter in Texas and fly to Alaska’s Interior and Arctic, some even continuing to eastern Siberia, to nest are lesser sandhill cranes, the smallest subspecies. The Canadian subspecies is a bit larger. It’s possible birds in Southeast belong to this group and have developed a different migration strategy.

The weekend after the crane festival, I was out in the hills around Fairbanks one afternoon and heard cranes calling. Looking up, I spotted a “V” of six cranes. They circled, catching a thermal and soaring increasingly higher, faint voices still audible. Finally, they broke free, barely visible against the clouds, and began their long journey on a route passed down through countless generations.

• Beth Peluso is a freelance writer, illustrator, and avid birder. She enjoys spying on wildlife around Alaska.

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