Cranes
Gruiformes
INDEX
WHAT ARE CRANES?
TYPES OF CRANES
CRANE FEATURES
SOCIAL BEHAVIOURS AND REPRODUCTION
CRANES, MAN AND CONSERVATION
CRANE-LIKE BIRDS OF THE BAHAMAS
CRANES OF ARDASTRA GARDENS
WHAT ARE CRANES?
Cranes are large, elegant birds that belong to the order Gruiformes, literally meaning "crane-like" but also includes many families of birds that do not look very much alike such as the coots, rails and limpkins. The cranes resemble the storks, herons and flamingos but they are only distantly related. They are large and beautiful birds known for their dramatic courtship and territorial displays which has made the crane a prominant symbol throughout many cultures.
Cranes have a varied diet and are opportunistic, taking whatever food is available. They are often found in wetland areas proding the mud for different creatures as well as foraging for vaious fruits. The cranberry actually got its name from being extnsively eaten by some Northern species of cranes.
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TYPES OF CRANES
The crane family is divided into two sub-families:
- Crowned cranes (Balearicinae) - Are an old group of cranes and have been around for at least 50 million years. In the past, there were many species and were found in many parts of the world but today there only two species survive and they are exclusively found in the warm climates of Africa.
- Typical cranes (Gruinae) - A recently evolved group of birds that have been on the planet for about 15 million years and today there remains about 13 different species. Unlike the Crowned cranes, these birds are much more cold hardy and are found in the North American tundra and Asian tundra, to the Asian, Australian and African tropics.
CRANE FEATURES
The cranes have many adaptations that help them to survive in their habitat.
Great day vision
Like most diurnal birds, they have excellent eyesight but the pupil is not big enough for night vision. Their skull is designed to slightly shade the eyes from the over head sun but the eyes are also positioned so that they can see straight ahead as well as the sides, above and below.
Foraging tools
The beaks of cranes are long and dagger-like. The beak is not as thick and strong for striking fish as herons do but it allows them to poke and prod creatures from muddy beds or pick up a number of different food items.
Long necks
The necks of cranes are long and agile, good for picking up food from the water without getting the bird wet. At the base of the neck, inside, the trachea (which all animals use to breathe and produce sound) is enlarged and even coiled in many species. This enables them to produce especially loud sounds which can carry over 5 miles in some species, particularly the true cranes.
Great flyers
Cranes have long, broad wings which are good for long distance flight or gliding. Many Northen species migrate vast distances every year. Some species glide for hours in the sky looking for better feeding grounds or just an opportunity for an easy meal. Their tails are short, making sharp turns nearly impossible, therefore their flight patterns are always slow and directional.
Many species of cranes therefore have heavily pigmented flight feathers, making them that little bit more resistant to the long distance flights. The heart and lungs are so efficient that cranes can get enough oxygen to fly even at high altitudes.
Herons and Cranes can be distinguished by looking at their styles of flight. The cranes always fly with their necks out stretched whilst the herons tuck thier heads in.
SOCIAL BEHAVIORS AND REPRODUCTION
Outside of breeding season cranes are very gregarious, living in very large flocks. All cranes are diurnal (active in the day) and spend most of their days, foraging for food, resting or preening (using the bill to distribute oil from a gland at the base of their tail. This oil waterproofs their feathers). At night they roost in their large flocks at traditional roosting sites.
Breeding season starts in spring in most species but in some species it coincides with rainy seasons when food becomes readily available. The social behaviours of cranes include a wide variety of visual displays and vocal displays but none are as impressive as their elaborate courtship dances. These dances help to facilitate pair bonding and are very complicated and specific to the species. Many juveniles can be seen also doing these dances as they learn them from the adults. Once the pairs are established, they leave the flock and establish their territory where they will begin nesting.
The females usually lay two large eggs. Both the male and female sit on the eggs and look after the chicks once they've hatched but the males are reported to do most of the feeding of the chicks. The chicks stay with their parents usually till the next breeding season where they join the rest of the flock and become nomadic. The young start to do their courtship dances as early as eighteen months but most do not actually breed until 3 years of age and some species as late as eight years.
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CRANES, MAN AND CONSERVATION
As with all animals that rely on wetland areas, the cranes are facing many problems. The largest problem being habitatloss. The areas where they feed and breed are being drained and often turned into agricultural land where farmers and cranes find themselves in competition with each other. In some countires cranes are hunted for food, trapped for the pet trade or are caught in electrical lines or accidentally shot. All cranes are at least considered to be vunerable species with 7 out of the thirteen species considered endangered. The Siberian crane being the most endangered of all the different species and is currently on the brink of extinction.
Conservation efforts are underway for many of the crane species, with hunting restrictions and protected breeding grounds but many species migrate over vast distances and therefore there needs to be a more universal approach to their conservation.
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CRANE-LIKE BIRDS OF THE BAHAMAS
There is a close relative of the cranes that is quite common in the Bahamas and also often seen in Ardastra Gardens. That is the Limpkin.
Limpkin
(Aramus guarauna)
This bird looks something inbetween a rail and a crane. It has long legs, drooping bill and is mainly brown with white spots. They fly more like a crane does and walks with a little limp, hence thire name. The Limpkin belongs to the "crane-like" order, Gruiformes but is in its own family, Aramidae. The Limpkin is found in the Southeast United States, Central and South America and the West Indies. They are solitary, living in swamps and marshes. They feed on a vaiety of items including mussels, seeds, small reptiles and frogs, insects. worms but their diet almost entirely consists of snails. Their beek is slightly bent to the right, prehaps enabling them to retrieve the snails easily from their shells. These birds normally nest on the ground and produce an average of about 6 eggs. They have also been called the "Crying bird" because of their loud and distinctive call that can be heard around nesting areas. Their populations throughout their range are healthy, however, in Florida they were nearly hunted to extinction in the beginning of the centry and so they are protected by law which has helped their slow return.
Limpkins are often seen in Ardsatra Gardens and usually outside of breeding season. However, they have begun to breed in the gardens and usually high up in the trees. Ardastra is very pleased to have this regular snail-eating visitor into its gardens and though they are shy they do not mind the presence of people and are now nesting in areas regularly visited by people.
CRANES OF ARDASTRA GARDENS
Ardastra gardens has the East African Crowned Crane.
East African Crowned Crane
(Balearica regulorum gibbericeps)
There are two sub-species of African-crowned crane. The East African crowned crane occurs from the Democratic republic of Congo through Uganda and Kenya to Eastern South Africa. This crane is found in the dry savannah habitats and nests in wetter habitats. The African crowned cranes (also referred to as the Grey crowned crane), together with the Black crowned cranes, are probably more closely related to a their ancient ancestors as they are the only genus to have a long hind toe used to grab ahold of branches as they roost in the trees, similar to pre-historic cranes. Although the East African Crowned crane remains common throughout much of its range, it faces threats to habitat loss, overgrazing and pesticide pollution. This crane is the national bird of Uganda.
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