Nature Blog Network

Wednesday, May 20, 2009

Crane parents compensate for colt's injury

---For photos on the Christy Yuncker Photo Journal webpage, click here.

Each colt is an individual. If a colt is injured, adults can compensate and delay their migration - apparently waiting for the colt to become flight-competent. We saw such compensation in 2008.

By 18 days of age, Oblio-08 was running
about waving her tiny wings in tandem with Roy (pictured to the right). But in early July, she began to favor her right leg, suggesting an injury. Although she continued to grow, she was physically hampered. For some weeks Oblio rarely ran and did not dance, jump or bound.  Roy and Millie postponed the basics of colt education and physical conditioning an tarried in Alaska to give her a chance to catch up.

Throughout June and July, Millie and Roy (the parents) were attentive, protective and frequently offered food. Yet Oblio seemed solitary, foraging 20-30 meters from her parents. (For photos, see Christy Yuncker Photo Journal) In contrast to other years, Roy and Millie danced little with each other and not at all with Oblio, perhaps reflecting their emotional state?

As the leg slowly healed, Oblio began to run a little and to flap her wings again in mid-August. Roy and Millie ran with her and then gave flight demos around the pond. As shown on Christy Yuncker Photo Journal, Oblio managed to lift off on August 26 at 74 days of age - two weeks late. Over ensuing days, Oblio tried several short flights around the pond. She gained competence and confidence.

On the morning of August 31, Roy and Millie spent hours purring, as if coaxing Oblio to fly. Finally, after several abortive attempts, all three lifted off. Oblio flew with her right leg hanging down, but they cleared the trees and disappeared across the valley. Three hours later, the cranes returned; the rest of the day was spent in preening and feeding.

Dancing became a staple activity of the family. Millie, Roy, and Oblio spent the next ten days feeding (every two hours) and dancing as a group of three - the first dances we had seen for over a month. Several times each day, the family flew off for an hour and then returned. At first, Oblio rested in the grass after these flights. At night, the family roosted across the valley (2-3 km distant).

Early September weather was mild and with each day, Oblio grew stronger. By September 10th, she was able to keep up with her parents (see Christy Yuncker Photo Journal).

On the morning of September 11, bouts of feeding and preening alternated every hour. At 11:05 AM, the three flew off to the south, then turned west down the valley and disappeared, departing (we hope) on their migration south. Departure had been delayed for almost two weeks while Oblio gained strength, yet the timing was auspicious since the first serious frost occurred only four days later.

Yumin Guo has described similar parental solicitude in response to injury of a hooded crane colt.

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