The swirling hordes of sandhill cranes that roost in the Platte shallows in March showcase one of the great wildlife migrations on our planet. The birds jostle one another like New Year’s eve revelers in Times Square. Individuals are lost in the mass of bouncing bodies. An alien from space, looking down on such a throng, probably wouldn’t guess that our fundamental social unit is a family. For cranes as for people, understanding the species takes more than gawking at a mob.
We have been privileged to study the social interactions within one particular sandhill crane family. Every April for over a decade we have watched “our” pair of cranes drop from the sky onto our backyard, a snowy bog near Fairbanks, Alaska. These birds, whom we know as “Millie” and “Roy,” left the Platte River valley two to three weeks earlier, as reported for a similar group of Fairbanks cranes followed by satellite tracking (Jason Caikoski and John Wright, Alaska Department Fish and Game). Upon arrival here, the pair vigorously defends their territory from intruding cranes. By comparing photographs of their detailed facial feather patterns and recordings of their unison calls from year to year, we are convinced that Millie and Roy are the same individuals whom we see every summer on our pond.
While Millie and Roy lingered on the Platte, stoking up for the 2,500-mile flight north, their family group probably included last year’s colt. When that colt left Alaska in September, it had brown eyes, cinnamon brown feathers on its back and wings, and short, whitish feathers covering its face and forehead.
During its first winter in the “lower 48,” a colt’s eyes take on a golden hue; body feathers molt to gray, and the forehead becomes nearly “clean-shaven,” revealing underlying reddish skin studded with wispy black bristles that is characteristic of adult sandhills. In March along the Platte we see some youngsters who are in the final stages of their cosmetic makeover. Most look like adults by the time they reach Alaska in late April.
Cranes mate for life. The adult pair bond and fidelity to their nest site endure year after year. The family is the foundation of the crane social system. Some birds, such as crows, have multigenerational families, with older kids from previous broods helping to raise new crops of hatchlings, but not so for cranes. Last year’s colt isn’t allowed to come back to the nest site that was its schoolyard all last summer. In early May we may see a single young bird land in Millie and Roy’s territory and, in one case, dance briefly on their marsh, but within a few minutes the interloper is gently challenged and ushered away.
Snow leaves us in mid-May and freezing temperatures return in early September. Ice on the pond thaws during incubation, and marsh vegetation is just starting to green up as the eggs hatch. Although a chick emerges from eggs as mobile and peck competent, it could not survive without months of protection and nurturing from its parents. In just three months each youngster must grow from a 4-inch, curious, toddling fluff ball to a 3-foot tall, feathered and semiskilled apprentice migrant.
Over the years we’ve watched and photographed—all day, every day—a total of six young crane colts mature over the almost continuous light of our subarctic summer. Last March in Prairie Fire, we described their activities in the first half of the nesting season.
The five academic subjects in Crane Summer Home Schooling are exploring, foraging, defense, dancing and flying. The school calendar is roughly consistent from year to year, but each colt and each summer brings different challenges. The colts are guided by attentive, doting and demanding parents who communicate with calls, purrs and body language. The birds are not automatons.
As crane colts dance with mom and dad, their performance improves with time and feedback. Dance is a social activity that is a dominant subject in the colt’s first summer of home schooling. With dance, cranes telegraph mood and intent. As dancing builds up flight muscles and improves coordination, it also refines social skills that will be important later, for courtship and social bonding with a mate.
Cranes have dancing in their genes. Young cranes become skilled dancers rather like young male songbirds acquire their territorial songs. For birdsong, the genetic template is refined by learning. Young male zebra finches babble like babies at 30 days of age. In succeeding weeks, they try to copy their memories of Dad’s song. Finally they refine their own songs by listening to themselves while experimenting with pitch and syllable structure.
In early summer a typical day for a crane colt includes foraging, resting and walking behind the parents. Occasionally the family disappears without warning, marching off into the black spruce forest. Sometimes they are absent for hours or even for overnight. Most of the time we don’t know where they go, and like a worried aunt and uncle, we anxiously await the return of the entire family intact.
Young chicks peer around and peck at almost any object. Their parents feed them berries, insects (Millie is the champion at catching dragonflies in flight), tubers and voles that Roy snatches from tunnels in the tundra. By early July the parents guide the colts’ attention toward ripening berries. In August the colts catch their own fritillary butterflies and search out other insects and spiders.
Except for eagles and lynx, few wild predators threaten adult cranes in our valley. But young crane colts could be easy prey for owls, ravens, gulls, as well as weasels and foxes. Using their wings, Millie and Roy shield tiny colts from marauding ravens and gulls, and they readily chase away red foxes with impressive droop-wing displays. In their first few years of nesting we suspect that our pair’s eggs or young might have been lost to foxes, but in recent years Roy confidently drives foxes from the territory by standing tall, spreading wings wide, leading with his long sharp bill and stalking forward.
In August great-horned owls often come to roost and to hunt squirrels or ducks in Millie and Roy’s territory. Owls are a potential problem for all pond residents. They are encouraged to leave by dive-bombing gulls, kestrels and gray jays. In one instance the crane family encountered an owl who stood in the grass, gripping a dead mallard in its talons. Millie and Roy cautiously approached with their feathers ruffled, while the gangly August colt jumped uneasily behind them. We’re not sure if the crane phalanx was guarding their territory or was hungry for a meal of fresh duck. Eventually the owl dragged its heavy prey into the underbrush, and the confrontation was over.
Millie and Roy dance all through the summer. In July the youngsters face off with a parent, squatting with wings cupped and looking vaguely like a Plains Indian chief’s war bonnet. As the month passes, dance training incorporates more and more runs across the bog with parents keeping pace alongside.
In late July, with flight training imminent, adult behavior changes. Instead of walking, Roy and Millie begin flying from place to place and around the pond while the colt watch intently. We suspect that these “demonstration flights” motivate the colt.
In August the colt sprints across the bog—jumping, flapping and even briefly catching air for a few feet. The liftoffs get longer and longer from day to day, until the colt is bounding across the marsh, running and jumping for distances of 30 feet or more. Bounding transitions into brief, awkward flapping-powered flight. The colt’s first flight is done solo, sometimes splash landing in the pond. But once liftoffs are mastered, the feathered student pilot takes short circling flights, escorted across the pond and over the territory. The colt goes first, with Roy overtaking to lead in flight and in landing. Soon thereafter the family rises over the trees and into the valley. The first valley excursions are day trips that leave the colt visibly tired on return. By late August excursions become overnight “campouts” that are probably practice for roosting during migration.
In 2010 the colt we dubbed “Lucky” didn’t keep pace on the first family excursion into the valley. He flew across the pond following Roy and Millie, but as they rose up over the treetops, he aborted and returned to his starting place on the bog. Roy and Millie looked back as they cleared the treetops, seeming surprised, and immediately returned to land beside the hesitant colt. On the next day Lucky was braver and followed them into the open valley.
One August evening in 2011 an intruder crane family of two parents and a colt landed on the other side of the pond. Millie, Roy and their colt (Hastings) flew together to eject the interlopers. Much jumping and flapping, involving all six cranes, followed. After 30 seconds, two adults and two colts went south over the trees. Roy and Millie stood in the tall grass at the battle site, looking left and right as they alarm called repeatedly. Hastings was nowhere to be found. After 20 seconds while still calling, they flew around the territory and soared south. As the noisy pair neared the center of Goldstream Valley, a youngster popped up from among the trees. It was Hastings. In the confusion of the melee, he had fled, following the wrong parents! Better that it happened here than at a migratory staging area, where we sometimes see single colts, peeping plaintively and apparently lost, flying above crane crowds, searching for their parents.
Concealment can be an effective defensive tactic. When danger threatens, a colt may disappear in the opposite direction while Millie and Roy deal with the intrusion. We term this behavior “flee and hide.” On Aug. 25, 2010, Christy heard an alarm call and looked out to see Millie and Roy agitated and jumping toward the west side of the bog. “Lucky,” their colt who had fledged on Aug. 7, was in the middle of the pond, swimming rapidly to the south. Suddenly a big animal, as large as an Alaskan husky dog, flashed onto the central bog. It was a lynx, who raced off into the woods as Christy snapped one picture. Rather than fly from danger, the colt swam away quietly while the parents stood ready and confronted a threat that fortunately was only transitory.
With one exception, our crane family has departed for migration on Sept. 1, 2 or 3. The exception was in 2006, when the colt “Oblio” somehow returned lame from a walking excursion in mid-July. A lame colt can’t dance or begin preflight training. For weeks Millie and Roy were attentive while they let Oblio initiate ragged little runs across the bog as he slowly recovered. As soon as he was able, they encouraged him by running in parallel and by family dancing. Most colts fledge in the first week of August, but Oblio did not take to the air until the 26th of August, over two weeks late. His entire school schedule had been delayed. Oblio, training at his own pace, became fully flightworthy by Sept. 8, just as the cottonwoods were turning bright yellow. One of his legs drooped slightly in flight, but the family migrated the next day, a week behind their usual schedule.
The departure for migration often begins with a long, high excursion to the south. One year we saw our crane family fly across the valley and rise into the clouds as they caught a thermal. We counted as they circled 29 times before peeling off over the ridge to begin their 3,000-mile, six-week journey to west Texas. Migration is fraught with known and unknown dangers, day after day. For the human stewards of Millie and Roy’s Alaska territory, it is a long, dark winter of worry.