Whooping Crane

The **whooping crane** (*Grus americana*), the tallest North American bird, is an endangered crane species named for its whooping sound. Along with the sandhill crane, it is one of only two crane species found in North America. The whooping crane's lifespan is estimated to be 22 to 24 years in the wild. After being pushed to the brink of extinction by unregulated hunting and loss of habitat to just 21 wild and two captive whooping cranes by 1941, conservation efforts have led to a limited recovery. In 2003, there were about 153 pairs of whooping cranes. As of February 2015, the total population was 603 including 161 captive birds.

## Description

An adult whooping crane is white with a red crown and a long, dark, pointed bill. Immature whooping cranes are cinnamon brown. While in flight, their long necks are kept straight and their long dark legs trail behind. Adult whooping cranes' black wing tips are visible during flight.

The species can stand up to 1.5 meters (4.9 feet) and have a wingspan of 2.3 meters (7.5 feet). Males weigh on average 7.3 kg (16 lb), while females weigh 6.2 kg (14 lb) on average (Erickson, 1976). The body length averages about 132 cm (52 in). The standard linear measurements of the whooping cranes are a wing chord length of 53–63 cm (21–25 in), an exposed culmen length of 11.7–16 cm (4.6–6.3 in) and a tarsus of 26–31 cm (10–12 in). The only other very large, long-legged white birds in North America are: the great egret, which is over a foot (30 cm) shorter and one-seventh the weight of this crane; the great white heron, which is a morph of the great blue heron in Florida; and the wood stork. All three other birds are at least 30% smaller than the whooping crane. Herons and storks are also quite different in structure from the crane.

Their calls are loud and can carry several kilometers. They express "guard calls", apparently to warn their partner about any potential danger. The crane pair will jointly call rhythmically ("unison call") after waking in the early morning, after courtship and when defending their territory. The first unison call ever recorded in the wild was taken in the whooping cranes' wintering area of the Aransas National Wildlife Refuge during December 1999 and is documented

## Habitat

The only remaining naturally occurring Whooping Crane population spends the winter on the Gulf Coast, primarily in Texas's Aransas National Wildlife Refuge, and breeds in Canada's Northwest Territories and Alberta, mainly in Wood Buffalo National Park. Surrounded by the headwaters of four rivers, the Canadian breeding grounds lie on poorly drained soil interspersed with shallow wetlands. The Whooping Cranes nest in potholes dominated by bulrushes and containing other aquatic plants such as cattails, sedge, and muskgrass. These wetlands are divided by narrow ridges that support white and black spruce, tamarack, willows, dwarf birch, Labrador tea, and bearberry. On their Texas wintering grounds, Whooping Cranes spend their time on estuarine marshes, shallow bays, and tidal flats, sometimes venturing to nearby farmland. Salt grass, saltwort, smooth cordgrass, glasswort, and sea oxeye dominate the marshes, with Gulf cordgrass on the margins. Farther inland in their range are sandy, gently rolling grasslands with live oak, red bay, and bluestem plants. Migrating birds feed in croplands and roost in shallow, freshwater wetlands.

## Diet

Whooping Cranes eat invertebrates, small vertebrates, and plant material, which they find on the ground and in shallow water. They peck and probe sandy or flooded soils to find prey underground. They also glean insects, berries, and seeds from low vegetation and take prey from the soil surface, using their bills to stab larger animals. The Canada breeding population eats mollusks, crustaceans, aquatic insects, minnows, frogs, snakes, mice, voles, aquatic tubers, and berries, while the Wisconsin breeding population eats mostly aquatic animals. Whooping Cranes also eat waste grains including barley, wheat, and corn from harvested fields, particularly during migration. On the Gulf Coast they feed in brackish bays, marshes, salt flats, and flooded or burned uplands away from human disturbance, eating mostly blue crabs, clams, and other animal foods, along with some plant material such as wolfberry, cranberry, acorns, cordgrass, marsh onions, and prairie lily.

## Nesting

Pairs choose nest sites in shallow water of marshes, sloughs, or lake margins, frequently on small islands. They often take advantage of vegetation that hides the nest and incubating parent from predators. Each year the pair chooses a new nest site, sometimes in the same vicinity. The male and female build the nest together by piling up and trampling vegetation such as bulrushes, sedges, and cattails. The nest measures 2–5 feet across and has a flat surface or a shallow depression for the eggs.

## Behavior

Whooping Cranes are monogamous, forming pairs at the age of 2 or 3 years and mating for life. Courting pairs perform an elaborate, energetic dance display in which they leap, flap their wings, toss their heads, and even fling feathers and grass. Each breeding pair has a territory defended primarily by the male, who may attack intruding Whooping Cranes by running, flapping, hissing, stabbing, or jumping and slashing with his feet. New pairs often establish a territory near their parents. Whooping Cranes live and travel alone, in pairs, as families, or in small flocks of up to 7 birds, and sometimes flock with Sandhill Cranes. They may ignore or pursue other nearby birds, cattle, and deer. They spend their time on the ground and in shallow water, never perching in trees. They learn migration routes and nesting locations from other cranes (or from researchers in ultralight aircraft, as part of reintroduction efforts). Their strong homing instinct limits their dispersal to new habitat.

## Conservation

The Whooping Crane is listed as federally endangered and is on the 2014 State of the Birds Watch List, which lists bird species that are at risk of becoming threatened or endangered without conservation action. The North American Waterbird Conservation Plan rates the species a 16 out of 20 on the Continental Concern Score and lists them as a Species of High Concern. Thanks to intensive conservation efforts, its population has grown from a low of 21 - 22 in 1941 to about 600 individuals in 2011 (with around 160 of these in captivity). Whooping Cranes were uncommon but widespread in 19th-century prairie marshes of the northern U.S. and southern Canada, and began disappearing with the arrival of agriculture and hunting. They benefited from the Migratory Bird Treaty Act of 1916, the establishment of Canada's Wood Buffalo National Park in 1922 (three decades before breeding grounds were discovered there), and the 1937 establishment of Texas's Aransas National Wildlife Refuge. Today's only self-sustaining population migrates between those two refuges. In 1967 the Canadian Wildlife Service and the U.S. Fish and Wildlife Service began captive breeding programs and reintroduction efforts, using Sandhill Cranes as foster parents. The first reintroduction attempt failed, but efforts continue and three reintroduced populations exist currently, sustained by captive breeding: a resident Florida population, a resident Louisiana population, and a migratory Wisconsin - Florida population. The latter has been taught to migrate with the help of ultralight aircraft. Factors threatening all of these small populations include powerline collisions, severe weather on the Gulf Coast, contaminant spills from barges, and occasional shooting by hunters mistaking them for Sandhill Cranes, or intentionally by vandals. Habitat management involves water control, restrictions on encroachment of trees and human disturbance, and maintenance of agricultural fields as food sources. The species' future depends on continued intensive conservation.