Bugeranus carunculatus

Geographic Range

Wattled cranes are found in the Ethiopian region of the world. They are comprised of three main populations. The smallest population is found in the highlands of Ethiopia, where they are isolated from the largest population residing in south-central Africa. Even further south in Africa, between Swaziland and Lesotho, populations of cold upland and semi-nomadic lowland wattled cranes are found. Southern Zambia, Mozambique, and Botswana are areas where wattled cranes are most populous.

The Kafue Flats sustain the largest population of wattled cranes, ranging from around 300 breeding pairs and around 3,000 individuals during peak season. Information about this population, however, is somewhat skewed because part of the population moves outside of the flats during seasonal changes and uses the flats as a staging area.

Wattled cranes once covered a greater geographic range in southern Africa, ranging from southern Tanzania to the southwestern Cape Province. This decline in geographic range can be attributed to cattle herding and food gathering before European settlement. Habitat destruction and disturbance by humans further limited the distribution of the cranes in Western, Eastern and Northern Cape Province after European settlement. Very few breeding pairs have been recently observed in Cape Province and Trasnkei. Present decline in geographic range is due to agricultural practices, afforestation, and the draining or damming of wetlands. Wattled cranes have been extirpated from Swaziland.

• Biogeographic Regions
• ethiopian ethiopian
  • native native

Habitat

Two extremely important habitats for wattled cranes are wetlands and grasslands. Wetlands make up around 76 % of the habitats occupied by these cranes, while grasslands make up around 10 %.

Wattled cranes occur in aquatic areas, preferably in sedge and grass wetlands along river bank floodplains. These areas are prime feeding and nesting sites for these cranes. Some notable wetlands sustaining populations of wattled cranes include the Kafue Flats, the Lukanga Swamp, the Sioma-ngwezi Plain in Zambia, the upper Chambeshi basin, the Luangwa Valley, and the Okavango Delta. Populations of 250 to 3,000 cranes can be sustained by one wetland during peak seasons.

Wattled cranes inhabit highland marshes in South Africa, Malawi, and Zimbabwe year round. The cranes utilize ephemeral and seasonal wetlands as areas for breeding or dispersal after breeding. Within Ethiopia they can live at elevations from 2,134 to 3,900 m. These populations in Ethiopia rely less on wetlands, with the exception of the breeding season. They typically inhabit montane grasslands, wet meadows, savannas, streams or marshes, and river bank areas. Outside of the breeding season, they can also migrate to plowed fields or areas of lower elevation and drier climates.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial
• freshwater freshwater

• Terrestrial Biomes
• savanna or grassland savanna or grassland

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• marsh marsh

• Other Habitat Features
• riparian riparian

Physical Description

Wattled cranes are the largest cranes in Africa. The wingspan of male wattled cranes ranges from 613 to 717 mm, compared with females ranging from 619 to 687 mm. The culmen, or upper part of the bill, ranges from 150 to 185 mm in males and from 124 to 183 mm in females. The tarsus, or cluster of bones in the feet, ranges from 298 to 342 mm in males and from 232 to 330 mm in females. Eggs are on average 101.9 mm by 65.3 mm in size and are estimated to weigh around 240 g. An adult male has been weighed to be 8,996 g and a female to be 8,285 g.

Adult males and females look the same, except that males have darker red bare skin than females. The head of wattled cranes is mostly white, with the exception of the dark gray feathered section above the eyes and on the crown. The common name "wattled cranes" is derived from the two almost completely feathered white wattles that hang from the upper throat. Wattled cranes have a very noticeable long white neck. Most parts of the midsection are shades of black, including the mantle, primaries, secondaries, tail coverts, and tail. The back and wings are a dusty gray color, while the breast is white. Legs and toes can be black or dark gray. While the bill is a light red to brown color, the iris is dark orange. The inner secondaries extend past the tail and come close to the ground.

Chicks have completely white heads and display lighter plumage color than the adults. Juveniles do not possess bare skin on the face like the adults do. Their wattles are also less conspicuous. Plumage on the juvenile body is a dull yellow color. Immature wattled cranes look similar to the adults, but their backs and under parts are a lighter shade of black and they do not have a black crown.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike
• male larger
• ornamentation ornamentation

Reproduction

Wattled cranes are monogamous birds that form pair-bonds that often last for life. Nest building is a part of a breeding pair’s courtship ritual, along with displays of jumping and dancing.

• Mating System
• monogamous monogamous

With an average clutch size of only one egg per breeding pair, the reproductive rate of wattled cranes is lower than any other crane. They can produce a clutch of two eggs, but usually only rear one of the eggs. Wattled crane eggs are incubated longer than any other crane, for 33 to 36 days. The pre-fledging stage, lasting 90 to 130 days, is also longer than any other crane. At around five months, the chicks will be able to fly. Although recorded during all months of the year at some point, peak breeding activity occurs from May to August.

Weather and landscape are important factors for breeding wattled cranes. The floodplains of Zambia, Botswana, and Mozambique provide a nesting area utilized by most wattled cranes at peak flood time. Peak flood time varies with each wetland due to environmental factors affecting water levels. Average flooding months are August and September. With receding water, chicks are reared in shallow areas.

The drier and cooler months of July and August are prime breeding times for wattled cranes that nest in smaller and more broadly distributed wetlands. During the rainy season from November to February, chicks will fledge. Populations of Ethiopian wattled cranes breed in May or June at the start of the high altitude wet season. Photoperiod changes can also affect breeding patterns for wattled cranes. Some sources indicate that wattled cranes reach sexual maturity at three to five years of age, while others indicate seven to eight years. When maturity is reached, the cranes will find a mate and create a pair bond that generally lasts for life.

Nest building is an important behavior of wattled cranes. They build nests out of large mounds of vegetation and surround it with a moat. This allows protection against predators.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• oviparous oviparous

Both parents care for the young constantly during the fledgling period, which may last 90 to 130 days. Chicks will remain with their parents until around one year old when the adult pair will be preparing to nest again. Nesting parents are very territorial, defending areas over a kilometer in size, and because of this they do not do well in areas with human disturbance. The adults build nests in open grass and sedge marshes with medium vegetation. They prefer the water level to be a maximum of one meter. The reproduction of wattled cranes is limited due to the declining number of acceptable nest sites and their territorial behaviors.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • male
    • female
• pre-hatching/birth
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female
  • protecting
    • male
    • female

Lifespan/Longevity

Currently, little is known regarding the lifespan of wattled cranes.

Behavior

Populations of wattled cranes are not typically nomadic, but they do occasionally move about due to varying water availability. Nomadism is more associated with the cranes that occupy seasonal wetlands, as opposed to permanent wetlands. Populations of wattled cranes that reside in the Kafue Flats are thought to travel to Botswana during periods of high rainfall. Some cranes move from wetlands in the Zambezi basin when water levels are very high to areas in Mozambique where the water recedes. Ethiopian populations, on the other hand, are migratory. They travel from Bale Mountain where they breed in November and December when the water level decreases and return in May and June as the rain replenishes the wetlands.

Juveniles display submissive behaviors as opposed to the territorial adults. After leaving the parents, the juveniles will join together to live, roost, and feed. Since the adults are highly territorial, the juveniles will find new places to carry out these activities away from established territories. Aside from the breeding season where wattled cranes are highly territorial, they can be quite sociable and form flocks with others reaching numbers up to 89 individuals.

Wattled cranes spend most of their day foraging. They have very specialized behaviors for this activity. There is no information regarding roosting or copulatory behavior.

• Key Behaviors
• flies
• diurnal diurnal
• motile motile
• nomadic nomadic
• migratory migratory
• territorial territorial
• social social

Home Range

Breeding wattled cranes defend the area surrounding their nest, which may be a square kilometer in size.

Communication and Perception

Wattled cranes utilize both visual displays and vocal calls to communicated with each other. Siberian cranes are the only other cranes that have a higher pitched call than wattled cranes. To make this high pitched sound, wattled cranes contort and move their necks. The female starts the call by lowering her head via coiling it near her shoulders then quickly extending her neck vertically with her head slightly angled in front of the neck. Her posture is maintained throughout the remainder of the call display, which is around three to seven seconds long. After she is done calling and starts movement, the male joins in by vocalizing in a similar manner. The female produces a short call in series, while the male produces a long and broken call with a series of short calls following. Like most birds, wattled cranes perceive their environments through visual, auditory, tactile and chemical stimuli.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Wattled cranes feed mainly on vegetation and insects; however, they have been known to eat frogs and snakes occasionally. Their main food source consists of water lilies and sedge vegetation. A large portion of their day is spent foraging through wet substrate. Upon locating a food source, such as insects or tubers, the crane intently probes its bill into the soil and digs. The crane will flail about using its large body as a digging force behind the bill. These cranes usually only dig as deep as their bill can reach, but they have been observed to immerse their entire head and neck under deeper water.

Soft soil covered by shallow water is a prime location to dig for food. This digging action comprises most of their foraging activity, but they have been observed pecking, picking up snails, and stripping grass for other food sources. To strip grass, cranes will clench the grass stem with their bills and strip the seeds by quickly moving the bill upwards. Wattled cranes can often be observed feeding along side of lechwes , a species of antelope that utilizes similar plant resources.

• Primary Diet
• omnivore omnivore

• Animal Foods
• amphibians
• reptiles
• insects
• mollusks

• Plant Foods
• leaves
• roots and tubers
• flowers

Predation

There is very little information available regarding predators of wattled cranes. It is thought that they have few predators due to their large body size as adults. Jackals are potential predators of crane chicks, while humans cause mortalities to young birds during land developments. Adult wattled cranes have been observed to hide their young chicks from predators in tall grass while they go off to forage elsewhere. This behavior is usually practiced until the chicks reach fledging age. Most often the chicks are quiet while hiding, but they will make a “chirruping” call to allow the adults to find them.

Ecosystem Roles

Very scant information is available about the roles that wattled cranes play in the ecosystem. However, it is hypothesized that they may be seed dispersers. They may also expose nutrients from the bottom of the wetlands by agitating soil with their bills while foraging.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Various conservation programs for wattled cranes and other species provide funds from eco-tourism that strengthens the livelihood of local communities.

• Positive Impacts
• ecotourism ecotourism

Economic Importance for Humans: Negative

There are no known adverse effects of wattled cranes on humans.

Conservation Status

Out of the six African crane species, wattled cranes are the rarest. The recruitment rate of wattled cranes was estimated to be 4.2 percent among a population of 784 adults. This estimate indicates that the cranes had a 13% pairing success, which is much lower than other crane species. The estimated age that wattled cranes first breed is around seven or eight years of age. This can have significant impacts on population success.

Wattled cranes were declared threatened by the International Union for Conservation of Nature and Natural Resources (IUCN) in 1988. From 1994 to the present year they have been listed as vulnerable. Data was last assessed in 2008. Their population has been estimated to be fewer than 8,000 individuals. With an insufficient understanding of population trends for these cranes, they are labeled as vulnerable on the premises that their small population has experienced rapid decline. Threats to their population are ongoing and possibly increasing.

Wattled cranes are highly dependent on wetland habitats for reproduction and survival. Wetlands are usually exploited for agricultural development, irrigation projects, hydroelectricity sources, mining areas, and more. With the degradation of these wetland habitats, populations of wattled cranes became seriously threatened. Small wetlands in particular are vital habitats for wattled cranes and are much more susceptible to damage via draining, damming, afforestation, and human habitation. As breeding sites of these cranes are sparsely scattered over a large range, fragmentation can significantly affect population numbers.

Reproduction and nesting is directly correlated with the flooding seasons of the wetlands for these cranes. With the advent of hydroelectric power interests comes the alteration of flood cycles, which in turn affect reproduction rates of the cranes. Hydroelectric operations have put limits on total wetland habitat, feeding areas, and nesting territories.

Grassland habitats are also critical to populations of wattled cranes. These areas have been altered via exotic timber plantations and agriculture. As humans take over territories for agricultural interests, wildlife populations, including wattled cranes, can be replaced by domestic livestock herds. A significant loss in the eggs and unfledged chicks can be attributed to management of wetland habitats through fire regimes. These fire breaks for farmlands are often carried out during vital winter breeding months for the cranes. Other forms of threats to wattled crane populations include inexperienced birds flying into power lines and removal of eggs for the international bird trade.

Genetic analysis has revealed differences between the South African and south-central African populations of wattled cranes. Due to this genetic distinctiveness between the two populations, the South African Crane Working Group has developed a Population and Habitat Viability Assessment (PHVA) in 2000 to evaluate the population dynamics of wattled cranes. This analysis evaluated various management approaches in hopes of enhancing the long term survival of the species. Population statistics are difficult to obtain and give a skewed view on the rate of decline of the species. With the population information available, the PHVA concluded that roughly two breeding sites per year are lost or abandoned due to habitat alteration.

The PHVA set goals for analyzing population dynamics of wattled cranes. These goals included closely monitoring population numbers, population locations, and all aspects of habitat degradation effects and proposing ideas for dealing with these issues. A central database was established to enter all of this data into. Specific models were constructed to analyze the data. Each event contributing to population structure change was evaluated from habitat loss due to industrialization and agriculture to mortality by means of power lines and fences, and accidental and/or purposeful poisoning, etc. This analysis also evaluated the effectiveness of captive breeding programs. This PHVA was carried out in collaboration with the Conservation Breeding Specialist Group. Conservation efforts of wattled cranes are still underway and require long term data sets to construct further results.

The Provincial Nature Conservation Ordinances also currently protect wattled cranes in all four provinces of South Africa. Tampering with the nests, eggs, or chicks of the cranes is punishable by law. These ordinances have also made it illegal to house captive cranes and to shoot, trap, poison, or injure cranes without conservation authority. The National Parks and Wildlife Act in Zambia and Malawi restricts hunting of the cranes and removal of crane nests. Varying amounts of protection are incurred by Designated Game Management Areas; however, human settlement is still authorized in some areas.

Other Comments

Bugeranus carunculatus is in the class Aves , order Gruiformes , and family Gruidae . The genus Bugeranus is represented solely by wattled cranes. Wattled cranes are also referred to as great African wattled cranes. Out of three crane species inhabiting South Africa, it is the largest, rarest, and most highly dependent on wetlands.

Additional Links

Encyclopedia of Life

Contributors

Ginger Ross (author), Northern Michigan University, Mary Martin (editor), Northern Michigan University, Rachelle Sterling (editor), Special Projects.

References

Boere, G., C. Galbraith, D. Stroud. 2006. Waterbirds around the world . Edinburgh: The Stationery Office Limited.

Coverdale, B. 2003. Breeding age and pair formation of Wattled Cranes, Bugeranus carunculatus, in the wild.. Ostrich: Journal of African Ornithology , 74 (3/4): 226.

Hancock, P., G. Maude. 2006. Key areas for wattled cranes Grus carunculatus in Botswana during summer. Babbler , 47: 8-14.

Hazevoet, C. 1997. On a record of the wattled crane Bugeranus carunculatus from Guinea-Bissau. British Ornithologists' Club. Bulletin , 117(1): 56-59.

Herremans, M. 2002. Migrant flocks' of Wattled Cranes Bugeranus carunculatus in Botswana.. Ostrich: Journal of African Ornithology , 73 (3/4): 166.

International Union for Conservation of Nature and Natural Resources (IUCN), 2010. "Grus carunculatus" (On-line). IUCN Red List. Accessed March 26, 2011 at http://www.iucnredlist.org/apps/redlist/details/143779/0 .

Johnsgard, P. 1983. Cranes of the World: Wattled Crane (Bugeranus carunculatus). Pp. 121-128 in Cranes of the World . Lincoln, NE: University of Nebraska-Lincoln. Accessed February 18, 2011 at http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1029&context=bioscicranes .

Konrad, P. 1981. "Status and Ecology of Wattled Crane in Africa" (On-line pdf). International Crane Foundation. Accessed February 16, 2011 at http://www.savingcranes.org/images/stories/pdf/conservation/CRAW_Pages_219-237_Wattled.pdf .

Macartney, P. 1968. Wattled Cranes in Zambia. Bokmakierie , 20(2): 38-41.

McCann, K., A. Burke, L. Rodwell, M. Steinacker, U.S. Seal. 2001. Population and Habitat Viability Assessment for the wattled crane (Bugeranus carunculatus) in South Africa. South African Wattled Crane PHVA Invitation: 1-169. Accessed February 18, 2011 at http://www.cbsg.org/cbsg/workshopreports/23/wattledcranephva_final_report.pdf .

McCann, K., G. Benn. 2006. Land use patterns within Wattled Crane (Bugeranus carunculatus) home ranges in an agricultural landscape in KwaZulu-Natal, South Africa. Ostrich: Journal of African Ornithology , 77 (3/4): 186-194.

Meine, C., G. Archibald. 1996. The Cranes: Status Survey and Conservation Action Plan . Cambridge, U.K.: IUCN, Gland, Switzerland.

Morrison, K., J. Bothma. 1998. Wetland nesting sites of wattled and grey crowned cranes on the Steenkampsberg Plateau, South Africa. South African Journal of Wildlife Research , 28: 110-120.