Due to the work the Crane Trust does in collaboration with other conservation partners, the following species are either flourishing or actively recovering on Crane Trust land.
» Whooping Cranes
The whooping crane (Grus americana) is not only the tallest bird in North America, it is one of the rarest.
There are approximately 300 whooping cranes in the wild, migratory flock that breeds in Wood Buffalo National Park in Canada and winters at Aransas National Wildlife Refuge in Texas. An additional 300 birds are either in captivity or part of re-introduction efforts, such as in eastern North America.
Since European settlers arrived in Nebraska in the 1840s, there have been written accounts of whooping cranes observed here during their spring and fall migrations. Never as numerous as sandhill cranes (Grus canadensis), whooping cranes reached the brink of extinction earlier in the last century. Only 15 birds remained in 1941 after more than a century of habitat loss and continuous hunting.
After 70 years of intensive conservation efforts, the population has increased but still faces many challenges. Their intrinsic rate of increase gives them the potential to double their population size in 8 years, as happened in the 1980’s. However, environmental and anthropogenic factors (including loss of habitat, altered wetland conditions, climate change and collisions with power lines) cause the population to recover at a much slower rate.
Whooping cranes spend the winter from November to March along the Gulf coast of Texas at the Aransas National Wildlife Refuge. Each spring from late March to late April, the cranes migrate to their breeding grounds in northern Canada at Wood Buffalo National Park and remain there from May through September. Hence, the wild population is often called the “Aransas-Wood Buffalo population” or “AWBP” referring to their wintering and breeding grounds.
Fall migration takes place from September through the end of November, when the last cranes arrive at their wintering grounds. Adult cranes that have a successful breeding season in Canada migrate with their chick(s). Whooping cranes normally lay two eggs, but usually only one egg/chick survives. On rare occasions the second egg survives, and adult pairs are seen migrating with their “twins”. In 2010, five pairs brought twins to Aransas, which was the second highest number of twins ever to reach the refuge. Whooping cranes are territorial at both their breeding and their wintering grounds and use the same territories year after year.
The migration route is long (about 2,500 miles) but narrow (less than 300 miles wide) and extends through Texas, Oklahoma, Kansas, Nebraska, South Dakota and North Dakota in the United States, and through Saskatchewan and Alberta in Canada.
Because the cranes’ migration route is so long, the International Recovery Plan for the Whooping Crane (2005) designated four sites along the route as “critical habitat”, meaning that this habitat “contains those physical or biological features, essential to the conservation of the species, which may require special management considerations or protection.” From south to north, they are: Salt Plains NWR, Oklahoma; Cheyenne Bottoms State Waterfowl Management Area and Quivira NWR, Kansas; and the Platte River between Lexington and Denman, Nebraska.
Along the Platte River, whooping cranes rest and feed in wet meadows, sloughs and crop fields and roost in the shallow waters of the river at night. Whooping cranes in the AWBP may make brief stops (one to a few days) on the Platte River before continuing their migration, and a few have spent more than a month on the Platte, especially individuals that migrate with flocks of sandhill cranes.
- Whooping cranes migrate as individuals, pairs, family groups and small flocks (5-12 individuals). However, during the spring migration of 2007, a record number of 34 individuals were observed together at Salt Plains National Wildlife Refuge, in Alfalfa County, Oklahoma (probably 4 groups), and during the fall migration of 2007 a record number of 30-35 individuals were sighted in one flock flying above Cherry County in northern Nebraska.
- On occasion, one or two individual whooping cranes will be observed migrating with flocks of sandhill cranes. These cranes tend to stay longer in Nebraska (22 to 33 days).
- In October 2010, eight whooping cranes were seen in western Missouri after strong winds blew them off course.
- Whooping cranes migrate primarily during daylight hours, but flights sometimes originate before sunrise and/or continue after sunset. Therefore, cranes can cover a large amount of ground in a long migration day and may never be spotted along the migration path. This explains why the number of sightings reported along the central corridor represents a low proportion of the total number of cranes migrating through the area.
- Radio-tracking of juveniles and subadults in the 1980’s revealed that some cranes could travel more than 500 miles in a single flight and approximately 1,140 miles in 2 days.
- Fall migration tends to be longer than spring migration. Fall migration is completed in an average of 29 days. Spring migration is completed in an average of 18.5 days.
» Sandhill Cranes
Each spring, more than 500,000 sandhill cranes gather in the Platte River valley during their northward migration. Sandhill cranes have been making this migration annually for thousands of years, and fossil beds in several parts of Nebraska contain the remains of prehistoric cranes from 10 million years ago.
The Platte is a “staging” area where the cranes stop to rest and replenish energy reserves before continuing on to their nesting grounds in Canada, Alaska and Siberia. It is the only major staging area on the sandhill cranes’ northward migration—approximately 80 percent of all the sandhill cranes come to the Platte every spring—and concentrations of cranes here are the greatest of anywhere in the world. The majority are lesser sandhill cranes (Grus canadensis), although some greater sandhill cranes (G. c. tabida) and Canadian sandhill cranes (G. c. rowani) also migrate through the central flyway. Though the subspecies differ in height and weight, they intermingle while along the Platte and are difficult to distinguish in the field.
Sandhill cranes migrate in individual family groups, but here at the Platte, the birds are social and gregarious, and numerous families gather into large groups while feeding and resting. A single meadow may contain as many as 100,000 birds. The cranes begin arriving at the Platte by mid-February and spend four to six weeks here each spring. The number of cranes peaks during the last half of March, though some birds remain on the Platte until mid April.
While on the Platte, cranes spend their days in the fields and meadows near the river, feeding on waste corn in crop fields and a variety invertebrates and plant tubers in wet meadows and grasslands. The cranes build up their body fat reserves, increasing their weight by 15 to 20 percent during their time here. They obtain the vast majority of their energy from corn (96 percent), but corn is not a complete diet. The sandhill cranes also need specific mineral nutrients and proteins for successful egg laying and reproduction, and animal prey—primarily snails, earthworms and insects—provides those essential nutrients. Animal prey is a minor portion of the cranes’ total caloric intake (4 percent), but it is critical that the birds get these nutrients for successful reproduction, so they spend almost half of their time searching for this part of their diet in the grasslands, wetlands and alfalfa fields along the Platte.
Late in the afternoon, sandhill cranes gather next to the Platte. As dusk approaches, they fly to the river and roost where shallow water covers the sandbars in the middle of channels. The wide, open, braided channels of the Platte provide ideal roost sites for the large concentrations of sandhill cranes—at the height of the migration, 50,000 to 100,000 cranes will pack into the most heavily used reaches in concentrations as high as 10,000 birds per half mile of river. The noise from so many birds calling is deafening, and some people liken it to being in a crowded football stadium. The cranes quiet somewhat when they go to sleep. At dawn, they awaken and disperse again to nearby feeding areas.
The Platte River region provides the combination of habitat components in close proximity to each other that the sandhill cranes need: crop fields with an abundant supply of food, wetlands and grasslands that provide critical nutrients, and secure roosting sites. The cranes are censused annually while they are here, and the mid-continent population has been stable or increasing during the past ten years. Recruitment into the population is approximately balanced by mortality due to hunting and other causes. During the fall, sandhill cranes are hunted in all states and provinces along their migration route except Nebraska.
The American bison, also referred to as buffalo, were once the dominant grazers of the Great Plains. These shaggy beasts can weigh more than a ton and are an iconic symbol of the prairie. Bison populations plummeted by the mid-19th century and by the late 1800’s less than 1000 remained. Today, the Crane Trust seeks to restore both the vision and the relationship these animals once had with the central Platte River.
Before their decline due to overharvest bison existed in vast migratory herds numbering in the millions. Because of their great numbers bison had widespread effects on the ecosystem. Expansive bison herds created nutrient-transfers of enormous magnitude by grazing and processing waste wherever they roamed. Bison disturbed the ground with their hooves creating wallows and trails void of vegetation, and existed in harmony with both the prairies and the Platte River. Grazing by bison kept the prairies in a constant state of repair and change, and is one of the processes land managers seek to mimic for grassland maintenance. Today there are more than 15,000 free-ranging bison in North America, and another 500,000 in fenced herds. However, the Crane Trust is one of just a few places in Nebraska where visitors can come to get a glimpse of these animals in their natural surroundings, and the only such place where cranes, bison, and the Platte River combine to give a glimpse of what once was.
» Interior Least Tern
With a weight of approximately 1 ounce and a length of approximately 9 inches, the interior least tern is the smallest of the gull and tern family. Males and females appear identical with a black crown, white forehead, gray back, gray wings above with white below, orange legs, and a black-tipped yellow bill. Immature birds have darker feathers, a dark bill, and dark eye stripes on their white heads.
The interior least tern arrives on its breeding grounds in Nebraska and other Midwestern states in early May to nest in small groups. They form their nests by scraping indentations in sandbars and gravel beaches. These nests may be lined sparingly with small shells or other debris. Eggs are commonly laid in clutches of 2 to 3 from late May through early August, and are incubated for about 20 days. The young fledge in 19 to 20 days. Nesting success depends on the presence of bare or nearly barren sandbars, favorable water levels during nesting, and abundant food. Interior least terns feed mostly on small fish caught by skimming the surface of the water or by making dives from the air. Least terns are very defensive and adults scream, dive, and sometimes defecate on intruders. By late August or early September, they migrate south to wintering grounds along the Gulf of Mexico. Interior least terns may live up to 21 years.
The interior least tern is an integral part of the fauna of Nebraska and, historically, flourished along the Missouri River and its tributaries including the Platte River. However, the interior least tern was listed as an endangered species in 1985. Loss of nesting and over-wintering habitat is the major reason these birds have declined in number over the years. Interior least terns require a sandy, beach-like surface mostly free of vegetation for viable nesting, which have been significantly reduced over the last half century due to dams, diversions, and other water management measures. Today, the total population of interior least terns is estimate at 17,000 to 23,000 individuals. As part of its overall habitat management plan, the Crane Trust actively contributes to the recovery of interior least terns by clearing vegetation from sandbars and sand pits for nesting on Shoemaker Island. Additionally, the Crane Trust collaborates with the U.S. Geological Survey and the Platte River Recovery Implementation Program, with support from the Central Platte Natural Resources District to band and monitor interior least terns nesting at the Crane Trust.
» Piping Plover
The piping plover is a small shorebird (about the size of a sparrow) that winters in the Gulf of Mexico and the Atlantic Coast and migrates to the Great Plains region to nest and raise their young. Piping plovers are characterized by a sandy colored back and white underparts with a single black neck band, a short stout orange bill, and orange legs.
They arrive on their Nebraska breeding grounds in early May, where they scrape nests in sandbars and gravel beaches and line them with small pebbles or rocks. The female lays three to four eggs, which are incubated by both parents. The eggs hatch after about 28 days, and the young leave the nest within hours and start foraging for themselves immediately. During this time, the parents’ role is to protect them from the elements by brooding them. When potential predators are nearby, adult piping plovers will often perform a broken wing display to draw attention to themselves and away from their chicks. It takes about 18 to 28 days for the young to begin flying, depending on food availability. Piping plovers start migrating south in August, and by mid-September most piping plovers have headed south for the winter.
The piping plover was listed as a threatened species in 1986. A major factor in population declines for this bird is the loss of suitable nesting habitat. Piping plovers require sandy, beach-like surfaces mostly free of vegetation for viable nesting. At one time, Platte River floods created piping plover habitat by keeping these areas clear of permanent vegetation. But dams, diversions, and other water management measures have significantly reduced this natural process, causing piping plovers to have to rely increasingly on managed habitat and sand pits for nesting. As part of its overall habitat management plan, the Crane Trust actively contributes to the recovery of interior least terns by clearing vegetation from sandbars and sand pits for nesting on Shoemaker Island. Additionally, the Crane Trust collaborates with the U.S. Geological Survey and the Platte River Recovery Implementation Program, with support from the Central Platte Natural Resources District to band and monitor piping plovers nesting at the Crane Trust.