Ardea goliath

Geographic Range

The range of Ardea goliath stretches throughout Africa, from Southern Egypt into South Africa. There are also populations reported in various patches of habitat in the Middle East and the Indian subcontinent.

• Biogeographic Regions
• oriental oriental
  • native native
• ethiopian ethiopian
  • native native

Habitat

Ardea goliath lives in large rivers, lakes, estuaries, swamps, marshes, and other freshwater and shallow saltwater habitats. It prefers areas with large fish to support its feeding habits. It has been observed at elevations of up to 2100 m.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial
• saltwater or marine saltwater or marine
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• temporary pools
• coastal coastal
• brackish water brackish water

• Wetlands
• marsh marsh
• swamp swamp

• Other Habitat Features
• riparian riparian
• estuarine estuarine

Physical Description

Ardea goliath is grayish-purple in color, with rufous or chestnut markings on its elongated neck, head and breast. It bears resemblance to its close relatives, purple herons ( Ardea purpurea ), but lacks distinctive black markings on its face and neck. It is also distinguished by its enormous size. At 1.5 m in length and 4.5 kg in mass, goliath herons are the largest of all living herons. They have a wingspan of 2 m.

Females are slightly smaller than males. Juveniles have more rufous, mottled breasts and bellies, and less distinct stripes.

In terms of systematics, goliath herons are most closely related to Sumatran herons ( Ardea sumatrana ) and white-bellied herons ( Ardea insignis ) of Southeast Asia.

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

• Sexual Dimorphism
• male larger

Reproduction

Ardea goliath typically forms monogamous mating pairs, in which both parents together guard the nest and raise chicks.

Little is known about the mating rituals of goliath herons, as observations of the rituals are not reported in the literature. It is known that the plumage becomes brighter during mating season, and a special dueting song occurs during the mating season. It is thought that observations of mating rituals may be absent because the birds re-pair with the same mates year after year, and therefore have little need to win over a new mate with a ritual.

• Mating System
• monogamous monogamous

The breeding season and interval varies with location of individual populations of Ardea goliath . The breeding season most commonly occurs with the start of the rainy season. However, in some places, breeding occurs year-round; in others, such as South Africa, breeding occurs biannually or less frequently.

Nests are constructed of sticks and twigs. The nests are at least 1 meter in diameter, and are typically found on islands in low vegetation (below 3 meters). Goliath herons sometimes nest with other birds in mixed rookeries, and sometimes solitarily. There have been some reports of birds abandoning nest sites when islands became a part of the mainland, which raises conservation concern for Ardea goliath , as preserving nesting sites is imperative to ensuring the species’ future.

Goliath herons lay a clutch of 2 to 5 eggs. The young hatch after an incubation period of 24 to 30 days.

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

Like most birds, both parents of Ardea goliath play active roles in raising chicks up to fledging. A typical clutch includes three or four pale blue eggs, of which typically no more than one or two chicks survive. Chicks are born altricial, with downy feathers and eyes closed. After 25-30 days of incubation, chicks are fed twice-daily through regurgitation by the parents. After five weeks in the nest, chicks leave but are still cared for by their parents for an adjusting period of 40 to 80 days.

Sibling rivalry and siblicide is common in many birds, and goliath herons are no exception. Competition within the nest makes chick survival difficult, and only 1-2 birds reach independence out of each clutch of 2-5 eggs.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female 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
• post-independence association with parents
• extended period of juvenile learning

Lifespan/Longevity

One account of Ardea goliath reports a maximum age of 22.9 years in captivity. Similar birds in the wild reach around 15 years of age at the oldest.

Behavior

Ardea goliath is a non-migratory species, though it may move to more favorable hunting habitat if the conditions warrant it. It is usually solitary during non-breeding season, but has occasionally been seen in pairs. The population density of goliath herons is not large enough to cause serious intraspecific competition or territoriality. It is only reported to defend its territory against predators.

Ardea goliath spends most of its time standing on its long legs in water, awaiting for prey to come nearby. It is a nocturnal feeder and is most active at night. When it does need to fly, to avoid a possible predator for instance, it does so with slow, deliberate wingbeats. Goliath herons are relatively skittish, and will fly away if anything it deems a threat approaches.

• Key Behaviors
• flies
• diurnal diurnal
• nocturnal nocturnal
• motile motile
• nomadic nomadic
• sedentary sedentary
• solitary solitary

Home Range

The home range and territory size of Ardea goliath is not known.

Communication and Perception

Goliath herons use primarily loud squawks to communicate. They attempt to detect prey mainly with vision. Their squawks vary greatly and include, from a “Kowoork” under normal circumstances, an “Arrk” in response to a disturbance, a “Kroo” and “Huh-huh” during stretching, and an “organ-like dueting”. The dueting is thought to be important for communication between members of a mating pair at the nest. Their sense of smell is relatively undeveloped and not relied upon by goliath herons. Like all birds, goliath herons perceive their environment through visual, auditory, tactile and chemical stimuli.

• Communication Channels
• visual visual
• acoustic acoustic

• Other Communication Modes
• duets duets

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

Food Habits

Ardea goliath opportunistically feeds on a variety of prey items, from carrion to amphibians, but prefers fish.

Ardea goliath typically feeds upon large fish, employing what scientists call a “Jackpot” strategy: goliath herons seem to pass up numerous opportunities to eat smaller fish in a gamble to not disturb the water and thereby be able to catch large ones. According to a 1980 study on feeding ecology, the average size of prey caught was around 30 cm, with only very few catches of prey less than 15 cm in length.

Feeding ecology influences many aspects of the behavior of Ardea goliath . Goliath herons typically land directly on mats of vegetation when possible, to reduce disturbance to the water. Mats of vegetation also frequently attract fish by providing food, and reduce other disturbance in the water so that it may be easier for goliath herons to detect subtle commotion caused by large fish swimming nearby.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore

• Animal Foods
• mammals
• amphibians
• reptiles
• fish
• mollusks
• aquatic crustaceans

Predation

Goliath herons have few natural predators due to their large size, watery habitat and ability to fly away from any ground- or water-dwelling predators. Some birds of prey, such as African fish eagles , may hunt juveniles or chicks, but as full-grown adults the risk of predation is low due to their large size.

Ecosystem Roles

Ardea goliath plays a role as a dominant predator of large fishes in the areas in which it lives, as it has few natural predators of its own. It is affected by many typical ectoparasites and endoparasites, including disease-causing viruses and bacteria, and digestive tract worms.

Economic Importance for Humans: Positive

Many birders enjoy watching goliath herons because they are large, unique and beautiful. It can therefore contribute economically to areas where Ardea goliath naturally occurs via tourism and birding. In India, goliath herons were formerly considered a delicacy and a royal gamebird with similar taste to the pheasant. It is now practically never consumed, due to its reduced range and habitat in this region.

Economic Importance for Humans: Negative

There are no known adverse effects of goliath herons on humans.

Conservation Status

Ardea goliath has been evaluated by IUCN as Least Concern because of its vast range and relatively stable, large population. It could potentially be threatened by habitat destruction or hunting in the future, especially in areas of the Middle East and South Asia where populations are small and patchy; but currently the species is not considered a conservation priority. In areas where populations are smaller and sparser, conservation of nesting areas is crucial to ensure the survival of the species.

Additional Links

Encyclopedia of Life

Contributors

Ethan Shirley (author), Michigan State University, Pamela Rasmussen (editor), Michigan State University, Rachelle Sterling (editor), Special Projects.

References

BirdLife International 2008, 2009. "Ardea goliath" (On-line). IUCN Red List of Threatened Species. Accessed July 22, 2009 at http://www.iucnredlist.org/details/144676/0 .

Kushlan, J., J. Hancock. 2005. The Herons . New York: Oxford University Press. Accessed July 25, 2009 at http://books.google.com/books?id=ktQEVY_10uQC&printsec=frontcover&source=gbs_v2_summary_r&cad=0#v=onepage&q=goliath%20heron&f=false .

Mock, D., K. Mock. 1980. Feeding Behavior and Ecology of the Goliath Heron. The Auk , 97(3): 433-448. Accessed July 25, 2009 at http://www.jstor.org/pss/4085837 .

2008. "Bio Facts: Goliath Heron" (On-line). Jacksonville Zoo And Gardens. Accessed July 26, 2009 at http://www.jaxzoo.org/animals/biofacts/GoliathHeron.asp .

2009. "Goliath Heron" (On-line). Oiseaux.net. Accessed July 25, 2009 at http://www.oiseaux.net/birds/goliath.heron.html .

2008. "Longevity, ageing and life history of Ardea Goliath" (On-line). AnAge. Accessed August 20, 2009 at http://genomics.senescence.info/species/entry.php?species=Ardea_goliath .