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Balearica regulorumgrey crowned crane(Also: grey crowned-crane)

By Margaret Thairu

Geographic Range

Balearica regulorum consists of two subspecies: East African crowned cranes (Balearica regulorum gibbericeps) and South African crowned cranes (Balearica regulorum regulorum). East African crowned cranes are found in Uganda and Kenya to Northern Zimbabwe and Northern Mozambique. South African crowned cranes are found in southern Angola and North Namibia and east through Botswana to Zimbabwe and south to South Africa. (Johnsgard, 1983; Walkinshaw, 1964; Walkinshaw, 1973; del Hoyo, et al., 1996)

Habitat

Grey-crowned cranes are usually found in grasslands close to bodies of water. They prefer to nest near bodies of water that provide cover. However they often feed in open savannas and grasslands. They can also be found in agricultural lands such as pastures, cropland, or fallow fields. In the south they are found in vleis. Vleis are shallow intermittent or seasonal lakes. They also often select habitats that include some trees, as grey-crowned cranes are one of only two crane species, along with black-crowned cranes, able to roost in trees. (Johnsgard, 1983; Walkinshaw, 1964; Walkinshaw, 1973; del Hoyo, et al., 1996)

  • Aquatic Biomes
  • temporary pools

Physical Description

Both sexes of breeding adults are similar except the male is slightly larger. Breeding adult grey-crowned cranes are known for their large yellow crowns. Each feather of the crown is tipped with black. Breeding adults also have pale grey to blue irises. Grey-crowned cranes have a bare white cheek patch with a reddish tint. In the sub-species, east African crowned cranes exhibit a redder cheek patch than South African crowned cranes. Black feathers surround the cheek patches at the base of these feathers. At the bottom of the chin there is a red gular sac (similar to a wattle, but inflatable). Grey-crowned cranes have a short grey bill. The neck feathers as well as most of the body feathers are a pearly grey. This is the one of the differences between closely related black-crowned cranes. The wings of grey-crowned cranes are mostly white but can have feathers that range in color from brown to gold. The tail is black and the upper coverts become a pale straw-like yellow. These cranes have black legs and a long hind toe that allows them to perch in trees. They weigh from 3 to 4 kg, and are 100 to 110 cm in length with wingspans of 180 to 200 cm.

Juveniles are generally grey with a brown crown and nape. Their irises tend to be brown. The gular sac that usually appears after four months is pink and as the crane matures gains the red coloration. Adult plumage is usually gained after 12 months.

Downy chicks of grey-crowned cranes are usually a pale buff with an ivory head. (Johnsgard, 1983; Walkinshaw, 1973; del Hoyo, et al., 1996)

  • Range mass
    3 to 4 kg
    6.61 to 8.81 lb
  • Range length
    100 to 110 cm
    39.37 to 43.31 in
  • Range wingspan
    180 to 200 cm
    70.87 to 78.74 in

Reproduction

Grey-crowned cranes are a monogamous species and appear to mate for life. During courtship they perform a ”nuptial dance” in which both birds participate. The display includes various bobbing and bowing actions as well as jumps. Either the male or the female can initiate the dance. It can begin in many different ways; the pair may be walking together nor not. The dance begins with a series of calls during which the gular sac is inflated. After which they both bob their heads, then spread their wings and begin a series of jumps. Either partner may call the display to a halt. (Johnsgard, 1983; Walkinshaw, 1973)

The breeding season varies with the rains. In east Africa it appears to be year round with peaks in the wetter periods. In South Africa and in drier regions, breeding mainly occurs during the rainy periods of Oct through April with peaks between December and February.

The usual location for a nest is in standing water or quite near it. Grey-crowned cranes also select areas to nest where there is an abundance of tall vegetation. The vegetation provides cover but allows the crane maximum visibility with only it head showing. They use vegetation that is close to the location for the majority of construction. The estimated sizes of the nests are 50 to86 cm in diameter, and 12.5 cm above water level.

Clutch size can vary from 2 to 4 eggs which is larger than other cranes that usually have a clutch size of 1 to 2 eggs. Newly laid eggs are a light blue. The eggs have an incubation period of 28 to 30 days. About 12 hours after hatching they are capable of swimming and float like little cork balls. They begin eating after 24 hours. By the second day of hatching they are able to wander with their parents in search for food and they return to the nest night for brooding. After the chicks hatch the family group does not forage in the savanna but instead keeps to the marshland where the tall grass can provide maximum coverage. Chicks fledge between 56-100 days after hatching. The juveniles will then join a flock containing other juveniles. Juveniles reach reproductive maturity at around 3 years old. (Johnsgard, 1983; Walkinshaw, 1964; Walkinshaw, 1973; del Hoyo, et al., 1996)

  • Breeding interval
    Gray crowned cranes breed once yearly.
  • Breeding season
    The breeding season varies with the rains, but generally peaks between December and February.
  • Range eggs per season
    2 to 4
  • Range time to hatching
    28 to 30 days
  • Range fledging age
    56 to 100 days
  • Average age at sexual or reproductive maturity (female)
    3 years
  • Average age at sexual or reproductive maturity (male)
    3 years

Males and females participate in constructing the nest. Both parents participate in the incubation of the egg. Like many cranes, Grey Crowned chicks are precocial. About 12 hours after hatching they are capable of swimming. They begin eating after 24 hours. By the second day of hatching they are able to wander with their parents in search for food and they return to the nest night for brooding. Parents tend to the young until they fledge at 56 to 100 days. They hide the young in tall marsh grasses then fly to nearby trees to roost. After fledging, the young join a group of other juveniles. (Johnsgard, 1983; Walkinshaw, 1973; del Hoyo, et al., 1996)

  • Parental Investment
  • precocial
  • male parental care
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • 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
  • extended period of juvenile learning

Lifespan/Longevity

Grey-crowned cranes may live up to 22 years in the wild or 25 in captivity. (Krajewski and King, et al., 2007)

  • Range lifespan
    Status: wild
    22 (high) years
  • Range lifespan
    Status: captivity
    25 (high) years

Behavior

Grey-crowned cranes have long hind toes that allow then to roost in trees, making them one of only two crane species able to do so. Grey-crowned cranes also display mutual preening, which may support pair bonds outside of the breeding season. Although their primary use is in mating rituals, dances are often performed outside of the breeding season as well. Though they are non-migratory, they move in relation to food sources and water. In the drier regions their movements are extensive. (Johnsgard, 1983; Walkinshaw, 1973)

  • Range territory size
    0.86 to 3.88 km^2

Home Range

Grey-crowned cranes are very territorial when it comes to nesting sites, however when it comes to foraging sites there have been no observations of a territorial display. Estimated territory size ranges from 0.86 to 3.88 square kilometers. (Johnsgard, 1983)

Communication and Perception

Chicks have a very sharp shrill “peeep”. Parents calling to the chicks usually use a low guttural “purr”. This is the same “purr” that they use when calling to their mates. The usual call of adult grey-crowned cranes is described as a low melancholy “oouuw” or “ya-oou-goo-lung”.

Grey-crowned cranes also utilize visual displays for attracting mates or deterring predators. They have two different displays when dealing with possible threats: a distraction display and an attack display.

There is no evidence for dominance hierarchies in this species. Like all birds, grey-crowned cranes perceive their environment through auditory, visual, tactile, and chemical stimuli. (Johnsgard, 1983; Walkinshaw, 1973)

  • Other Communication Modes
  • duets

Food Habits

These cranes have a very general, omnivorous diet. They are known to eat insects, small animals such as lizards and worms and seeds. Some have been observed to stamp the ground to disturb the insects. Grey-crowned cranes often utilize disturbance by other species in foraging for insects. Like cattle egrets, they have been observed following cattle and eating flushed insects. They also feed on newly plowed fields. They usually eat seeds of sedges and grasses. They are also known for eating maize. They prefer to eat the maize directly from the cob, knocking out kernels, instead of eating the kernels found scattered around. (Johnsgard, 1983; Walkinshaw, 1973; del Hoyo, et al., 1996)

  • Animal Foods
  • reptiles
  • insects
  • terrestrial worms
  • Plant Foods
  • seeds, grains, and nuts

Predation

Grey-crowned cranes may be predated upon by domestic dogs. Roosting in trees is an adaptation that helps to avoid many terrestrial predators. It is suggested that foraging alongside large livestock such as cattle serves to deter predators as well. ("The Cranes. Status Survey and Conservation Action Plan Grey Crowned Crane (Balearica regulorum).", 2006)

  • Known Predators

Ecosystem Roles

Seeds make up a portion of grey-crowned cranes' diets, thus the birds are likely an important seed disperser for the plants. Grey-crowned cranes also are a food source for predators such as domestic dogs.

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

Grey-crowned cranes are known for being wonderful pets and survive well in captivity. They are also the national birds of Uganda. Cranes that forage for insects in agricultural fields may benefit farmers by reducing crop pests. (Johnsgard, 1983)

Economic Importance for Humans: Negative

Grey-crowned cranes are sometimes persecuted due to their use of agricultural land for foraging. Often when foraging in fields they may uproot seedlings and damage crops. They also forage on maize and other grain crops, which directly reduces crop yield for farmers. (Mafabi, 2000; Olupot, et al., 2009; Walkinshaw, 1973; Beilfus, et al., 2007)

  • Negative Impacts
  • crop pest

Conservation Status

Grey-crowned cranes are currently not endangered but populations are rapidly declining. The major threats that grey-crowned cranes face is the loss and degradation of wetlands. Other factors that are leading to the decline are the increased use of pesticides and decreased practice of leaving fields fallow. Pesticides are killing a food source (insects) for gray-crowned cranes as well as poisoning the birds. Fallow fields provided an extra foraging area especially with the increase of wetland development and degradation. But with the decline of such areas food is becoming even more scarce. (Mafabi, 2000; Olupot, et al., 2009; Beilfus, et al., 2007; Beilfus, et al., 2007; IUCN, 2009; Mafabi, 2000; Olupot, et al., 2009)

Other Comments

Other Common names: Blue-necked cranes, Royal cranes

Classification: Grey-crowned cranes are a descendant of the most primitive of the living Gruidae. Primitive species of crowned cranes date back in the fossil record to the Eocene period.

Two Sub-species: East African grey-crowned cranes (Balearica regulorum gibbericeps) and South African grey-crowned cranes (Balearica regulorum regulorum) (Johnsgard, 1983; Krajewski and King, et al., 2007; Walkinshaw, 1973; del Hoyo, et al., 1996)

Contributors

Margaret Thairu (author), Florida State University, Emily DuVal (editor), Florida State University, Rachelle Sterling (editor), Special Projects.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
duets

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

marsh

marshes are wetland areas often dominated by grasses and reeds.

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

social

associates with others of its species; forms social groups.

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

young precocial

young are relatively well-developed when born

References

2006. "The Cranes. Status Survey and Conservation Action Plan Grey Crowned Crane (Balearica regulorum)." (On-line). USGS Northern Prairie Wildlife Research Center. Accessed December 06, 2010 at http://www.npwrc.usgs.gov/resource/birds/cranes/baleregu.htm.

Beilfus, R., T. Dodman, E. Urban. 2007. The status of cranes in Africa in 2005. Ostrich: The Journal of African Ornithology, 78: 175-184.

IUCN, 2009. "BirdLife International 2009. Balearica regulorum" (On-line). Accessed February 12, 2010 at http://www.iucnredlist.org.

Johnsgard, P. 1983. Cranes of the world. USA: Bloomington: Indiana University Press.

Krajewski and King, 1., 1. Krajewski et al, 2. Fain et al. 2007. "Gruidae" (On-line). Tree of Life Project. Accessed February 11, 2010 at http://tolweb.org/Gruidae/26312/2007.08.31 in The Tree of Life Web Project,http://tolweb.org/.

Mafabi, P. 2000. The role of wetland policies in the conservation of waterbirds: the case of Uganda. Ostrich: The Journal of African Ornithology, 71: 96-98.

Olupot, W., H. Mugabe, A. Plumptre. 2009. Species conservation on human-dominated landscapes: the case of crowned crane breeding and distribution outside protected areas in Uganda. African Journal of Ecology, 48: 199-125.

Walkinshaw, L. 1964. The African Crowned Cranes. The Wilson Bulletin, 76: 355-377.

Walkinshaw, L. 1973. Cranes of The World. USA: Winchester Press.

del Hoyo, J., A. Elliot, J. Sergartal. 1996. Handbook of the Birds of The World. Vol 3, Haztin to the Auks. Balencia: Lynx Edicions..

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