The Blue Crane

Filed under: High Risk Terrestial Birds |

The Blue Crane (Anthropoides paradiseus) belongs to the family Gruidae and is South Africa’s national bird.

The blue crane is currently listed as vunerable in the Eskom Red Data Book of South Africa, Lesotho and Swaziland and the 2010 International Union for the Conservation of Nature and Natural Resources (IUCN) Red List.  There are many threats facing the blue crane such as poisoning, illegal trade, habitat destruction, power line collisions, active persecution by landowners and many more.

Although the blue crane faces many threats, many conservation measures have been put in place to protect the species by various conservation bodies like the South African Crane Conservation Programme of the Endangered Wildlife Trust and the Overberg Crane Group. These groups have managed to form wonderful working relationships with landowners whose property the cranes live on, their staff, as well as the general public, in an effort to protect the blue crane.

DISTRIBUTION

The blue crane is a near-endemic to South Africa with a small isolated population of about 60-80 birds occurring around the Etosha Pans in Namibia and a few isolated birds in Botswana and Swaziland.  It is the most range restricted of all the cranes in the world and is abundant in limited areas of its range, but is rare in most areas of South Africa.

Within South Africa there are three main strongholds of this population.  The first is in the Overberg/Swartland regions of the Western Cape Province, the second is the central Karoo population of the southeastern region of the Northern Cape province and the western regions of the Eastern Cape province extending into the southern regions of the Free State, while the third is situated along the eastern section of the country and includes the southern parts of Mpumalanga, the northeastern Free State and parts of KwaZulu-Natal.

Historically, blue cranes occurred mainly in the grassland biome along the eastern section of the country.  The loss of the natural grasslands in the Free State, Northern Province, Mpumalanga and KwaZulu-Natal, and the replacement of the natural vegetation with wheat and dryland pastures in the wheat producing regions of the Swartland and Overberg in the Western Cape, changed the distribution and demographics of the blue crane population.

Today the largest numbers of blue cranes can be found in the Western Cape (± 12 000 birds), with a smaller population in the Northern/Eastern Cape (± 5 000 birds) and the rest (± 5 000 birds) occurring in the remainder of its current distribution range.

HABITAT

Blue cranes are mostly independent of wetlands and this allows them to be more widespread than the other crane species within South Africa.  With regards to natural vegetation, within South Africa the species can be found in the open grasslands and the grassland/Karoo ecotone, while in Namibia it occurs in the grasslands and dwarf shrublands fringing the pans.  The species is frequently found in agricultural fields and in the Western Cape it is restricted to cereal crop fields and dryland pastures.

FEEDING HABITS

Evidence suggest that the blue crane is primarily vegetarian and eats small bulbs, seeds and roots.  They do, however, eat a variety of insects (locusts, termites, caterpillars, grasshoppers, beetles, etc.), worms, crabs, fish, frogs, reptiles, and small mammals.  The blue crane is often reported doing damage in various agricultural crops, like wheat, barley and lucern.  In most cases the birds are feeding on spilled grain.  In the Overberg, they regularly feed from feed bins set out for sheep and ostriches.  Birds feed mostly by pecking, but they do dig using their bills.

BREEDING HABITS

Blue cranes only pair with one mate (monogamous), and despite being very social animals are extremely territorial while breeding, driving any other blue cranes from the breeding territory.  They nest in summer and the laying date can be anytime between August and April. Non-breeding birds form non-breeding flocks during this period.  After the chicks have fledged, they together with the adults join the non-breeding flocks to form large over-wintering groups.

Blue cranes nest in wetlands, open grasslands, Karoo and agricultural areas, where all-round visibility is good.  The birds often return to the same area and nest in the vicinity of the previous year’s nest.  Generally the nest is a scrape in the ground with a few stones and sheep dung scraped together.  In wetlands, however, they usually nest on a pad of vegetation.

A pair of blue cranes is said to mate for life and display a wonderful courtship dance which comprises of the two individuals jumping up and down with their wings extended. The birds are mature at about three to five years of age.  They usually lay two eggs with an incubation period of 30 to 33 days and both male and female incubate the eggs. Both chicks are frequently reared with each attempt and are fed on an initial diet of insect larvae and worms. The chicks are able to fly at about three to five months. The parents are very protective of their young and will guard them aggressively.

Mortality of chicks is high during the first year and is caused by a variety of disturbances. The following breeding season, the young juveniles will join the large flocks of non-breeding birds.

MIGRATION

Blue cranes are migratory only within South Africa and only within certain regions.  Little is known about the migratory habits and published statements are often contradictory.  In the Western Cape, evidence from satellite tracking and colour ringing suggest very localised movements within this region.

MOULTING

Blue cranes are known to go through both a partial moult as well as a complete moult, when they become flightless.  On the Agulhas plains, blue cranes go through a synchronised moulting during the second half of summer.  Birds going through flightless moult form large flocks in areas where disturbance is less frequent and close to water bodies into which they can escape when threatened.  Birds going through a complete moult tend to be skittish and move away at the first sign of disturbance.  The cranes seem to use specific sites for moulting and these sites need to be identified and conserved. The time needed to re-grow flight feathers could take up to two months.

 

information from :

http://www.bluecrane.org.za/index.php?option=com_content&view=article&id=53&Itemid=65

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