County birds: the Sandhill Crane family is doing fine

These photos are of the Sandhill Cranes that nested this spring near our home in Orono, hatching two colts (chicks). My guess, based on their plumage and growth, is that the young birds hatched in mid-May. The photo of the colt stretching its stubby wings was taken June 4. The other photos were taken June 29. They are growing fast. The birds weighed about one-quarter pound at hatching, following 30 days of incubation. The young birds were standing within hours of hatch, and could walk away from the nest within 24 hours.

(There is more on the cranes in my column in today's — Wednesday — StarTribune, Variety section, Home and Garden pages.)

The colts began feeding as soon as they left the nest, taking bits of food from their parents. After about two weeks the young birds would be expected to have tripled their birth weight. Thirty-five days after hatching the young birds would have increased their body weight about 14 times. My estimate is that the in the most recent photos the colts are over 35 days old. By the end of July the bill and wings of these birds will be near adult size. Growth will be complete at 10 months.

Sandhill Cranes lay from one to three eggs for their annual nesting. Two eggs is average. One colt often dies because, it is believed, of sibling rivalry. Eggs hatch one each day, so one colt has a slight head start. Aggressive dominant behavior begins almost immediately. If food is plentiful, however, both colts can survive without problem. The colts in these photos apparently are being raised in a territory with abundant food resources; both are doing fine. The biggest threat to their survival now are the coyotes that live here.

The birds nested in a large cattail marsh adjoining a small meadow. This is where the family spends its days and nights. The colts are learning to find food. I've watched the parents pull worms from the ground to feed the colts, the young birds closely watching the parent probe the ground. A friend watched one of the adults kill a young Green Heron, which was eaten.

The young birds will make their first flights approximately eight weeks after hatching. That puts these birds on schedule to fly in about three weeks. They're practicing now, running across the meadow grass with wings flapping. One of the adults begins the exercise, running, then flying low across the ground, the colt following, but not airborne yet.
The cranes will migrate when winter weather drives them out. In Crex Meadows near Grantsburg, Wisconsin, resident cranes, and the thousands of migrant cranes that stage there in fall, generally leave in November. I haven't watched these local cranes closely enough to know when they depart. The four will leave as a family. The young birds will be independent of their parents early next spring. They will breed sometime between their second and seventh years.

An adult pair of cranes has been using this nesting location for several years; it is presumed the same birds are returning.

Fossil records for this Sandhill subspecies (there are three) date to 2.5 million years ago. Cranes are among the oldest living bird species.

All of this information comes from the Sandhill Crane monograph in the Birds of North America series (number 31 in the series) published several years ago by The American Ornithologists Union and The Academy of Natural Science in Philadelphia, Penn. Authors are T. C. Tacha, S. A. Nesbitt, and P. A. Vohs.

Above, a colt on June 4. Below, the colt on June 29, learning to dig for worms.

Below, a flying lesson, the colt, top, running beside one of its parents.