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Refuge Notebook: Ascent of the cranes

Posted: October 31, 2013 - 3:17pm

After three weeks of nearly continuous rain in August on the Kenai Peninsula, the second Sunday in September was Indian summer perfection: sunny with just a hint of autumn crispness. The Skilak Lookout Trail was still soggy underfoot, but we immediately saw the “fruits” of all that moisture: Highbush Cranberry branches loaded down with plump red fruit, and the forest floor festooned with mushrooms of incredible variety. We duly noted the abundance of fresh berry-laden bear scats.

Once out of the forest and into the more open post-fire shrub regrowth, our daughter Allyson with her keen hearing (mine having suffered from too many years around airplane engines) said “Listen — a flock of cranes!” Once our trail chatter silenced, I could hear it too, and we soon beheld the source: a flock of 60 Sandhill Cranes several thousand feet up and spiraling skyward like dry leaves in a whirlwind. The birds had found a column of rising air kicked up by the mountain slopes, and were using it to gain altitude for their migration over the Kenai Mountains. They continued their noisy but graceful aerial dance, soaring ever higher with only an occasional flap of wings. Finally, as little more than tiny specks in the sky, they maneuvered into one continuous broad “V” and headed off rapidly eastward, riding a strong upper level west wind. A few stragglers pumped a bit to take their place in the lineup. Over the next hour we spotted more flocks precisely emulating the first.

This strategic use of vertical air currents to aid migration is common for cranes, storks, hawks, eagles and other soaring migrants, as well as human pilots, but the event took me back to October 1982 when I first witnessed it firsthand. I was helping with an international study of the critically endangered Whooping Crane in northern Saskatchewan.

At that time there were only about 40 Whoopers left in the wild that nested in Wood Buffalo National Park in northern Alberta and Northwest Territories, and wintered in Aransas National Wildlife Refuge on the Gulf Coast of Texas. Crane researchers were alarmed and frustrated at the number of young cranes produced each year that mysteriously disappeared during their fall migration, so they came up with an unorthodox approach to get some answers.

The plan was to capture a couple of Whooper “colts,” attach solar-powered VHF transmitters, and follow their migration. Each crane family was followed by two people in a Cessna aircraft and a ground crew in a 4WD truck. The aerial crew located its crane family each morning via radio-tracking receiver, then maintained visual contact through the day at a distance that minimized disturbance. They maintained radio contact with the ground crew, who barreled down the road in their truck to arrive as soon as possible at the cranes’ selected overnight roosting site. There they too would camp for the night, record site location, habitat notes and bird behavior, and alert the waiting aerial crew the following day when the cranes took off on the next leg of their journey.

I was the biologist-pilot who flew one of the aircraft, accompanied by Canadian Wildlife Service crane biologist, Ernie Kuyt. The trip was quite an adventure in many respects but, referring back to our current Alaska story, the typical daily migration flight sequence was really intriguing. Our crane family migrated as a unit and, once in the northern Saskatchewan prairies, they spent most of the cold overcast days with unfavorable winds feeding in grain fields.

But on sunny days they would take off around 10 a.m. and fly to the nearest large dark surface — usually a fallow farm field. Once over this sun-warmed spot, they would pick up a thermal convection air column and circle to remain in the rising air, soaring effortlessly to heights of 6,000 feet, where the thermal dissipated. Using the altitude gained, they glided, with little wing flapping, to the next fallow field along their southward journey. The process was repeated until about 3 p.m. when thermals petered out. The researchers hypothesized that crane parents were intentionally providing their weak and inexperienced offspring with a relatively low-effort migration. 

The conclusion of our Whooping Crane odyssey was disturbing, but did provide insight into the problems encountered during migration. For some reason our crane family changed their pattern in late October, flying long days at odd hours, often after dark, when there were no thermals for soaring. With no free lift from thermals, there was no efficiency to be gained by climbing, so they flew very low over the prairies. Sadly their chick died in a collision with a power line near Waco, Texas — just 200 miles short of Aransas.

On a happier note, the Wood Buffalo-Aransas Whooper population, though still not “out of the woods,” now numbers 280 birds, thanks in large part to the dedicated efforts and ingenuity of both professional biologists and conservation-minded volunteers.

On our way back to the car from Skilak Lake, we listened intently but unsuccessfully for a last note of far-off crane music, as we basked in the alpenglow and the autumn dress of the surrounding hills. In my mind I wished “our” sandhill cranes Godspeed on the perilous journey to their winter range.

 

Bill Larned retired after 36 years with the U.S. Fish and Wildlife Service as a Wildlife Biologist/Pilot and resides in Soldotna. You can find more information about the Refuge at http://kenai.fws.gov or http://www.facebook.com/kenainationalwildliferefuge.

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