Cranes!

Sandhill cranes in Vermont

by Bruce MacPherson

April 29, 2008.  Bristol  Pond.  6:45 P.M.  42  degrees  F. Overcast.  No wind.  A single Sandhill Crane just flew into the marsh south of the boat access parking lot.

Those are my field notes from that April evening.  But Sandhill Cranes in Vermont?  You bet!  For the past 3-4 years Sandhill Cranes have been sighted regularly in Vermont and in 2007 a pair of Sandhill  Cranes successfully fledged a single chick.  This information was dutifully recorded in the most recent Vermont Bird Breeding Atlas Survey.  This year this pair of cranes returned to Vermont and produced two “colts”, as young cranes are called. Here is some background information about one of Vermont’s newest resident bird species.

All told there are 15 species of cranes worldwide, but only two species of cranes inhabit North America-Whooping Cranes, which are endangered, and Sandhill Cranes, which are thriving.  In fact, there are over 600,000 Sandhill Cranes in North America.  The breeding range of Sandhill Cranes extends from Siberia, through Alaska and western Canada to the Pacific Northwest and the northern Midwestern states. Vermont is at the far eastern edge of the Sandhill Crane’s range, but, who knows?  Perhaps their range is expanding as their population grows.

The winter range of Sandhill Cranes includes  south Texas, south-central New Mexico, Arizona, and northern Mexico.  Cranes also gather in staging areas during their Spring and Fall migration. More on this later.

Cranes are ancient birds. In fact, a 10 million year old crane fossil was excavated from the tar pits found at the Ashfall Fossil beds in Nebraska and a Sandhill Crane fossil identical in every detail to modern Sandhill Cranes was carbon-dated at 2,000,000 years old.  Apparently, Sandhill Cranes can adapt successfully to a changing environment.

Five Sandhill Crane subspecies have been described in the ornithological literature, two of which are migratory and three of which are not. Migratory Sandhill Cranes include the Greater and Lesser subspecies. Some authorities also include an intermediate-sized subspecies on this list-the Canadian subspecies. However, where cranes mingle on their wintering grounds, these  intermediate-sized birds overlap at both ends of the growth spectrum with Greater and Lesser Sandhll Cranes and cannot be reliably distinguished from them by either morphological criteria or DNA analysis.

The non-migratory subspecies are found in Cuba, Florida, and Mississippi. The Sandhill Crane population  in Florida appears to be stable, but both the Mississippi and Cuban subspecies are endangered.

Sandhill Cranes are majestic birds, somewhat resembling herons and egrets. Herons, egrets, and cranes are not closely related, though. Great Blue Herons and Great Egrets are assigned to the family Ardeidae,  whereas cranes occupy the family Gruidae. The scientific name for Sandhill Cranes is Grus canadensis.  Sandhill Cranes are 3-4 feet in length with a wing span approaching six feet. They have three long toes  on their feet  attached to long, featherless legs.  Cranes also have a vestigial posterior toe. However, unlike herons and egrets, cranes are unable to grasp branches. Accordingly, cranes roost on the ground, rather than in trees or perches like herons and egrets. Also, cranes fly with their neck extended in contrast to herons and egrets which fly with their neck coiled.

Sandhill Crane plumage is gray overall, but often their feathers take on a rust color due to “painting”  with iron-rich soil during preening. In addition to their long, dagger-shaped bill, adult Sandhill Cranes have a distinctive red crown, which becomes more prominent when they are excited, and a white face patch. In general, Sandhill Cranes are so distinctive that differentiating them from herons and egrets is not difficult.
And Sandhill Cranes dance! With enthusiasm! Why cranes dance is not fully understood, but this behavior probably serves as a courtship ritual during breeding season and a means of communication between cranes otherwise. Body posturing generally is a feature of crane behavior which may signify a warning to other cranes in the area that are vying for territory, a predator alert , or simply a sign from a leader saying “Let’s go.” Similarly, Sandhill Cranes utter a vast number of vocalizations to each other, including distinct contact, flight intention, location, and alarm calls.

Sandhill Cranes are omnivores, their diet consisting of grains, mice, snakes, frogs, eggs, and insects. However, on their staging grounds 80% of their diet consists of waste grain, especially corn. Managing the crane population on their wintering grounds and staging areas, where thousands of Sandhill Cranes gather, represents a formidable challenge, since a single Sandhill Crane consumes up to a half pound of grain per day. At the Rowe Audubon Sanctuary in Gibbon, Nebraska, where 500,000 Sandhill Cranes congregate for a month in March and April  before leaving for their breeding grounds, cranes eat about 1600 tons of waste corn during their stay.

Sandhill Cranes become sexually mature at 2-6 years of age and typically hatch 1-2 eggs in breeding season. Nests typically are constructed in a marsh surrounded by water where cranes roost at night. This habitat provides protection from nosy (and noisy) predators, who might attack the nest. Since on average Sandhill Cranes live about 25 years, they may produce a large number of offspring during their lifespan. Cranes are monogamous more or less and the family unit stays together during migration. Accordingly, scanning large flocks of Sandhill Cranes when they are on their wintering grounds reveals small clusters of cranes mingling and flying together. These birds represent family units.

In November, 2007, my wife Pam and I attended the 20th annual “Festival of the Cranes” at Bosque del Apache NWR in San Antonio, New Mexico. This festival celebrates the return of over 5000 Sandhill Cranes to their wintering grounds. We attended a variety of workshops and field trips, many devoted to Sandhill Cranes as well as the large variety of waterfowl and raptors that inhabit the refuge. One of our instructors was Keanna Leonard, the education coordinator at Rowe Audubon Sanctuary in Nebraska, the staging area for over 500,000 Sandhill Cranes in March-April. Keanna graciously agreed to answer a few questions about Sandhill Cranes for this article. Thanks to Bill and Mae Mayville who generously provided photographs of the Bristol Pond Cranes.

Cranes! A Conversation with Keanna Leonard

1. Keanna, during March and April, the Rowe Audubon Sanctuary, where you work, probably hosts more Sandhill Cranes than any other place in the world. What makes Rowe so special? How was your season last year?

The big bend region of the Platte River in central Nebraska does host the largest concentration of any Cranes in Vermont
species of cranes in the world. From around Valentine’s Day to Tax Day (April 15th) we see over 500,000 cranes. Rowe Sanctuary is located just yards from the some the most pristine river habit that cranes use for roosting.

We had around 12,000 visitors from all 50 states and 44 countries last year to witness what has been dubbed one of the top ten wildlife spectacles in the world.

2. The Sandhill Crane population seems to be thriving. Have Sandhill Cranes always been numerous or is this a recent phenomenon? Do you perceive any major threats to the population down the road?

In the 70’s it was reported that there were around 300,000 sandhill cranes. Over the past 30 years the population has grown to over a half million. The staging area along the Platte River is considered the critical point in the central migration route. Cranes stay in the area for approximately three weeks eating enough food to add around 20% to their body weight. The extra weight allows them to finish their migration north in good condition and ready to begin the nesting season. For those cranes who are looking for a mate, the Platte River is also considered the night club of love. The major threat is the loss of habitat. The river is diverted, dammed, supplies water for residential, industrial, agriculture, and recreational use. What is left over is for wildlife. The river is also threatened with invasive species such as phragmites, purple loosestrife and now salt cedar. We work with many other conservation organizations negotiating water usage and keeping the river channels clear and usable for the cranes and other animals that prefer wide, open, sandy channels – such as whooping cranes, piping plovers and least terns.

3. As you know, Sandhill Cranes are beginning to appear in the Northeast, including Vermont. Is there good evidence that Sandhill Cranes are expanding their range?

We have heard that cranes are moving into new and previously abandoned territories. That is good to hear!

4. The Sandhill Crane population is currently large and stable, whereas Whooping Cranes are endangered with less than 500 individuals alive in the United States. How do you account for the striking difference in the success of these two related birds?

Actually in this flyway we had over 250 whoopers migrate north this spring! With the introduced eastern population there are now around 400 whooping cranes. To put it simply, many have surmised that whooping cranes are just pickier when it comes to both habitat and food than Sandhill Cranes.

5. Where can birders go to find out more about Sandhill Cranes? Do you have a favorite book or reference?

I recommend that anyone who would like to read more about Sandhill Cranes find these two books: On Ancient Wings by Michael Forsberg and Crane Music by Dr. Paul Johnsgard. Good websites include the International Crane Foundation (www.savingcranes.org), Platte River Whooping Crane Maintenance Trust (www.whoopingcrane.org) and of course our website at www.rowesanctuary.org. Don’t forget to check out the Crane Cam that runs live throughout March and April. A great DVD is Crane Song by the NET Foundation for Television.

6. If Vermonters would like to plan a trip to the Rowe Audubon Sanctuary in Nebraska to see the Sandhill Cranes, what is the best time of year to visit? Do you conduct an organized program of lectures and field trips during the crane season?

The best time to see Sandhill Cranes is the first of March through the first week of April. We conduct field trips to our viewing blinds twice a day – 6:30 A.M. and P.M. - to watch cranes leave or come back to the river. During the day throughout the season we offer public educational programs. If people would like to get more involved, we also conduct one of the oldest wildlife conferences in the United States, the Rivers and Wildlife Celebration. We also offer families the chance to learn about cranes together at our Family Crane Carnival. If you are not able to come to Rowe, do check out the Crane Cam on our website.
To make reservations or to learn more about next year’s events, just give us a call at 308-468-5282.

7. I am confused about the subspecies of Sandhill Cranes. What is the basis for splitting out the Canadian subspecies from the lessers and greaters? Or is this separation not warranted?

Most biologists have dropped the Canadian subspecies. In the field it can be difficult to distinguish lessers from greaters, but basically the lesser sandhills are 20% smaller. Through this flyway we have the majority of the lesser Sandhill Cranes in the world, but we also see greaters.

8. I was surprised to discover that hunting Sandhill Cranes is permitted, although cranes are covered under the Migratory Bird Treaty. What is the impact of hunting on the Sandhill Crane population?

Most of the states in the western part of the United States do hunt Sandhill Cranes. Nebraska is the only state in the central migratory route that does not hunt them, in fact. Right now we are seeing no obvious impact of hunting on the growth of the crane population, though.