Nature Notes: Sandhill Crane
It was just after dawn as I drove north along Route 123 on a beautiful sun-streaked August morning. Passing the huge Merriconegan farmhouse, I noticed the salt marsh was nearly full at high tide. Suddenly my eyes were drawn to a sight I could hardly believe. Amidst the wildflowers and field vegetation stood a tall visitor to Harpswell that I had seen only once before in central Maine.
The visitor was a sandhill crane, a bird with an ancient history, a troubled recent past and an encouraging near future. Cranes have long been revered in many cultures including by the Japanese and indigenous people of North America. There is much to learn about these unusual birds “from away.”
Sandhill cranes were first reported in Brunswick, Maine in 1961, and were not confirmed as breeding in Maine until 2000. In the seminal book Birds of Maine, author Peter Vickery describes sandhill cranes as “uncommon migrants” and rare breeders in our state’s wetlands. Twenty years later roughly two dozen pairs of birds are reported in Maine most years. Despite warming temperatures the birds have been reported to overwinter here just once.
So what are these strange, somewhat ungainly creatures and why are they in Maine? Of 15 species of cranes worldwide only two are found in North America, the sandhill and the larger whooping crane. Brilliant white, the whooping cranes are endangered and limited to just a few Western sites. At a time when so many bird species are in decline, the sandhill crane is staging an impressive comeback from near extinction.
With most breeding carried out in far northern Canada and Siberia, the cranes scientific name is Antigone canadensis. The common name “sandhill” comes from the habitat of important stopover points of the cranes’ migration routes, particularly Nebraska’s famed Sandhills region. It is there that fossil records from 10 million years ago established the sandhill crane as having one of the longest known histories of any living bird.
Currently six species of sandhill cranes are recognized by scientists, only two of them with healthy populations. The greater sandhill crane is the predominant bird east of the Mississippi River. As a result of habitat loss and excess market hunting their numbers had fallen to fewer than 1,000 birds by 1940. Thanks to conservation efforts and the birds’ resilience, the current population is estimated at 100,000 and growing. As a result you can now see sandhill cranes in new areas like Maine and New Jersey. The lesser sandhill of Western North America numbers around 400,000-500,000 birds
Adult cranes are predominantly light gray in color. During the summer the bulk of their feeding takes place where the soils are rich in iron, and the birds transfer that iron from their bills to their feathers resulting in russet tones that are beautiful in full sunshine. In contrast to the gray plumage, adult cranes sport a large red patch behind their long sharp bill with white cheeks. The iris is a striking reddish orange.
Standing more than four feet tall, the cranes are similar in stature to our common great blue herons. Heavier female cranes may reach 15 pounds. On the move these birds cut quite a figure thanks to a wingspan that nears eight feet. Those wings are critical to the cranes’ migration since they can soar up to 15,000 feet on warm thermals and glide hundreds of miles a day with a modest energy expenditure.
Sandhill cranes are native to the original vast wetlands and grasslands of North America. The favorite habitats for breeding are open freshwater wetlands and marshes but birds may also use sedge meadows, grasslands and even agricultural fields if conditions are favorable. Breeding begins around age three and birds are paired for years in normal circumstances. Arriving in a suitable Maine wetland in April, the pair builds a nest of grassy material generally floating on the water.
While the crane has a rather awkward appearance, the rituals of mating allow them to show off their graceful side. The birds have an elaborate ritual of bowing, nodding and calling to each other. The ritual includes a dance involving both male and female with jumps and kicks that result in pair bonding, also attracting many human admirers.
The female lays one to three eggs although it is unusual for more than one chick to survive the rearing time. Both adults incubate the eggs during the month-long wait. But the female plays the primary caregiving role with the newborn chicks. The tiny birds are born covered with fluffy down, their eyes soon open and they can walk within a few hours of hatching if necessary. The young birds grow at a rapid rate, attaining near adult size in just two months and also using their new wings in flight.
If there is a defining characteristic of these unique birds it would be loyalty. Not only are the cranes loyal to their mates they are likely to stay within small family groups for a year or more. Season after season cranes follow the same migration routes of their past and make stopovers for rest and feeding at the same locations, some of which may harbor many thousands of birds.
These cranes are mostly vegetarians with a particular focus on high nutrition agricultural grains. During September through November migrations you will most likely find cranes during the day in crop fields consuming ripe corn or remnants in harvested grain fields. Yet the cranes are also known for their willingness to consume a range of animal foods such as insects, crustaceans, eggs and small mammals or reptiles. Scientists believe these dietary supplements provide vital minerals and amino acids to their diet.
As large, rather slow-moving creatures sandhill cranes attract many predators. Four-legged hunters like fox, raccoons, coyotes and bobcats will take eggs or cranes if possible. Ravens, crows and gulls will take eggs or chicks while raptors like hawks, owls and eagles will pursue larger birds. Cranes are not well equipped for aggressive defense but will either scare off predators with loud calls and threatening displays or use their sharp bill, large wings, strong legs and sharp toes to inflict injury.
Sandhill cranes are reported by scientists as living an average of seven years although Cornell’s Birds of the World notes several tagged birds that survived beyond 35 years. Even though they are large by avian standards, cranes live in an environment full of risk beyond predation. While fewer wetlands are lost these days, ongoing development encroaches on crane haunts each year. Changes in agricultural practices and favored crops have a big impact on food supplies especially during migration. Overpopulation of competing species like snow geese can impact nesting success in breeding areas. An increase of invasive plants can degrade the value of wetland habitats. High tension power lines and wind turbines sometimes cause crane deaths.
Another distinctive feature of these cranes is a wide range of vocalizations, over a dozen of them used regularly. Whether trumpeting, bugling, rattling or croaking, the cranes can manipulate their airways to create unique and dynamic sounds that carry long distances. I have heard cranes at one mile or more even in the windy conditions of the Canadian prairie. The birds use soft purrs and clucks when communicating with a partner or chick at close range but when mating or mounting a defense the calls really ratchet up in volume and intensity.
Seeing the crane in Harpswell seemed a positive omen because I was just two weeks away from a trip to Alberta and Saskatchewan from where I am writing. It has been fascinating to see thousands of these unusual birds on the wing or on grain fields in this vast agricultural area. With luck we’ll all see more cranes in Maine in coming years.
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