Crane

Cranes are a collection of tall bird species with long legs. There are 15 different species of these birds in the world, usually having brown, white, or gray coloring. Different species of these birds live across every continent except South America and Antarctica, typically breeding in the north and flying south to warmer climates for the winter. America’s largest bird is the whooping crane, standing five feet tall and spreading wings up to seven feet. They are known for being highly social birds that perform elaborate dances to attract lifelong mates. 

Scientific Name

Fifteen different species of these birds live across five continents. All of these magnificent birds belong to the class Aves, order Gruiformes, superfamily Gruoidea, and family Gruidae. The name crane is of Germanic origin, the words Kran in German and kraan in Dutch. At the same time in history, in the 16th century, the word developed through Middle English as ‘crane’. The word means to “cry hoarsely.” Now, the word is also used to describe someone stretching out their neck or limbs like the bird, as in, “He craned his neck.”

Evolution

As part of the order Gruiformes, cranes are also related to rails, also known as Rallidae, finfoots or Heliornithidae, and limpkins or Psophiidae. Scientists believe that the existing genera of cranes, including Antigone, Balearica, Grus, and Leucogeranus, emerged on the evolutionary scene about 20 million years ago during the early part of the Miocene (which itself lasted between 5.33 and 23 million years ago).

Asia is home to the largest number of species, eight. Next in line is Africa, which is home to six species, two of which are somewhat arboreal, while North America is home to two, as is Australia.

Types

Subspecies of these birds and their warm-season habitats include:

• Common crane (Grus grus):  This bird is capable of measuring 51 inches in length and weighing over 13 lbs. ‘It has a wingspan of about 8 feet and is the most widespread species of crane in Europe, though other species such as the Demoiselle Crane can also be found in southeastern parts of the continent.
• Red-crowned crane (Grus japonensis): Known for the patch of red skin on their crowns, these birds are capable of growing to 5 feet 2 inches in height and weighing up to 23 lbs. They can be found in East Asia.
• Sandhill crane (Grus canadensis): This species has a maximum height of 4 feet 6 inches and an average weight of 10 lbs. It is generally gray and can be found in Siberia and North America.
• Sarus crane (Grus antigone): Its claim to fame is its status as the tallest flying bird, with a maximum height of 5 feet 11 inches. Found in India, Southern Asia, and Australia, it is capable of weighing up to 26 lbs.
• Whooping crane (Grus americana): This species is capable of reaching a height of 5 feet 3 inches and weighing 19 lbs. Its wingspan is about 7 feet 7 inches, and it is native to North America.
• Demoiselle Crane (Anthropoides virgo): Found in northwest Africa, Ukraine, and southern Russia, as well as central and eastern Asia.
• Blue Crane (Anthropoides paradiseus): This bird, found in South Africa and Namibia, is the national bird of South Africa.
• Wattled Crane (Bugeranus carunculatus): Found in Ethiopia, South Africa, and southern Africa.
• Siberian Crane (Leucogeranus leucogeranus): Found in western Siberia and northeastern Siberia.
• Hooded Crane (Grus monacha): Found in northeastern China and southeastern Russia.
• Black Crowned Crane (Balearica pavonina): Found in western and eastern Africa.
• Grey Crowned Crane (Balearica regulorum): Found in southern and eastern Africa.
• Brolga, Australian Crane (Grus rubicunda): Found in Australia and northern New Guinea.
• White Naped Crane (Grus vipio): Found in Mongolia, northeastern China, and far eastern Russia.
• Black Necked Crane (Grus nigricollis): Found in northern India, western China, and central China.

Appearance & Behavior

These birds are the world’s tallest flying birds, and range in size from only 35 inches long to 69 inches long. The Demoiselle is the smallest, and the Sarus Crane is the longest. But the heaviest one is the Sarus Crane, which can weigh up to 26 pounds. The birds all have long legs, long necks, large wings, and streamlined bodies. Their wingspan varies, with their wings having a rounded appearance. Males and females look the same, but males are a bit larger.

The feathers and markings vary according to their habitat. Open wetland birds typically feature more white in their coloration than species from forests or small wetlands. The birds living in the forest or small wetland habitats feature more grey. The white birds generally grow larger, too. Smaller forest birds with their darker coloring can blend into their environment better while nesting. Of these forest dwellers, Sandhill cranes and common cranes apply mud to their feathers to better hide from predators.

‘All of these bird types, except the Blue, Wattled, and Demoiselle cranes, feature bare skin on their faces. They use this skin to communicate with other birds by expanding and relaxing their muscles. This activity also changes the color of their face. Blue, Wattled, and Demoiselle cranes can move the feathers on their head to signal their flock, too.

These birds have special throat features that help them communicate. Some have a shorter windpipe that only presses gently upon a bone in their chest. Others have a longer windpipe that presses deeply into the bone in their chest. Still other species of cranes have fused bones of the windpipe and chest that give more power to their calls. In this last group, the calls can travel as far as several miles. 

These birds’ calls include a large vocabulary. They start learning these special calls that work like human language from the time they hatch. Their first calls beg for food from parents and signal that they are content or need parents’ attention. They soon learn alarm calls and calls that signal that they are about to launch into flight. They recognize each other by their calls and even form duets.

During breeding season, these birds become very territorial and stay on their own territory full time. During the non-breeding season, many species of these birds form large flocks, socialize, engage with each other, and feed together. The birds that eat mostly plants feed in flocks, but the ones that eat meat feed in family groups and rejoin the flock for rest or travel. These birds need to stick together in groups to keep themselves safe when resting, protect their young, and socialize.

Habitat

These birds live on all continents except South America and Antarctica. Africa and East Asia have the most variety of these birds living in one region. Africa has six species, whereas East Asia has six during its peak season. With 15 different species among the broader family of cranes, each type has its own preferred habitat.

Most of them need wetlands for their survival, as well as broad, open areas. The majority also nest in the shallows of wetlands, while some nest there but move their chicks to grassy lands for daytime feeding. Only the two types of African crowned cranes do not roost in wetlands. Instead, they roost in trees.

Not all of these birds migrate with the changing seasons. Some are sedentary, which means they stay in one region throughout the year. Of those that fly to warmer weather for winter, many travel thousands of miles to their breeding habitats. 

Diet

These birds are omnivores. They can eat both animals and plants. Preferred foods on land include seeds, nuts, acorns, leaves, berries, and fruit. They also eat insects, birds, small reptiles, small mammals, snails, and worms. While living in wetlands, they feed on roots, tubers, rhizomes, snails, frogs, and small fish. Their diet is highly adaptable according to their location, time of year, and food availability. However, the birds with shorter beaks prefer dry upland foods, and the ones with longer bills prefer wetland foods.

The birds feeding in wetlands dig for tubers and rhizomes. This requires them to stay in one place for a long period of time as they dig and expand a hole searching for these foods. They also lower their heads and move very slowly forward with their bills probing for insects and small animals.

To reduce competition, two species living near each other adopt their own habitats. This prevents overfeeding on available foods and ensures all have access to nutrition. For example, in China, Siberian cranes feed in shallow water and mudflats while their neighboring White Naped cranes feed on the edges of the wetlands. At the same time, Hooded cranes in this same area feed on meadows and agricultural fields, sharing the fields with common Eurasian cranes. 

Predators & Threats

Because adult birds are so large, few predators challenge them in their natural habitats. But some predators do exist and include other large birds of prey, such as owls and eagles, as well as foxes and wildcats. Chicks are highly vulnerable to these ground-based predators.

People take over their habitat and threaten these birds through urbanization. This affects population numbers by driving cranes away from their breeding, roosting, nesting, and feeding grounds. 

Reproduction, Babies, & Lifespan

These birds are monogamous. This means they have a lifelong mate. They typically find their mate during their second or third year of life. But they do not successfully breed for several years. To attract a mate, young birds perform a mating dance. They flap their wings, bow, jump, and throw small sticks or plants.

During their first breeding attempts, they often fail. Sometimes this period of failure leads to a “divorce” of the birds to find new mates. As long as they breed successfully, a male and female will stay together in their lifelong pairing.

Scientists studied Sandhill cranes in Florida. Of these 22 pairs, seven couples stayed together for 11 years. Of the 15 that did not stay together, just over half of the relationships ended because of one of the birds’ deaths. About 18 percent of the birds divorced, and scientists could not track 29 percent of the pairs.

These birds breed according to the individual breeding season of their species. The season depends on local climate and conditions. Migrating birds breed immediately upon arriving in their summer habitat, from late spring to early summer. Tropical birds typically prefer to breed during wet or monsoon seasons.

The eggs hatch about a month after laying. When the chicks hatch, their parents feed them until the babies can fly away from the nest. This is typically after two months. Young birds can reproduce at three to five years of age.

Wild birds typically live for 20 to 30 years. In captivity, a Siberian crane lived for 83 years. 

Population

Because there are so many types of these birds, the population varies widely. Conservation status also depends on the individual species.

Below is the conservation status of each of the 15 types of cranes in the world today, according to the International Union for Conservation of Nature:

• Eurasian (Common) Crane has a population of 590,000 to 660,000 birds and is listed as Least Concern.
• Sandhill Crane has a population of 450,000 to 550,000 birds and is listed as Least Concern.
• Demoiselle Crane has a population of 230,000 to 261,000 birds and is listed as Least Concern.
• Blue Crane has a population of 17,000 to 30,000 birds and is listed as Vulnerable.
• Wattled Crane has a population of 6,000 to 6,300 birds and is listed as Vulnerable.
• Siberian Crane has a population of 3,500 to 4,000 birds and is listed as Critically Endangered.
• Hooded Crane has a population of 6,000 to 15,000 birds and is listed as Vulnerable.
• Whooping Crane has a population of 50 to 249 birds and is listed as Endangered.
• Black Crowned Crane has a population of 44,000 to 74,000 birds and is listed as Vulnerable.
• Grey Crowned Crane has a population of 20,100 to 24,600 birds and is listed as Endangered.
• Sarus Crane has a population of 13,000 to 15,000 birds and is listed as Vulnerable.
• Brolga, Australian Crane, has a population of 35,000 to 74,000 birds and is listed as Least Concern.
• White Naped Crane has a population of 3,700 to 4,500 birds and is listed as Vulnerable.
• Red Crowned Japanese Crane has a population of 2,000 to 2,650 birds and is listed as Vulnerable.
• Black Necked Crane has a population of 6,660 to 6,800 birds and is listed as Near Threatened.