Agamia agamiagami(Also: Agami heron; chestnut-bellied heron)

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Geographic Range

Agami herons (Agamia agami) occur primarily in South America, with their core distribution in the Orinoco and Amazon basins. Sightings have been recorded as far north as southern Veracruz and Neuvo Leon, Mexico. Their range also extends from eastern Mexico in the north, through Guatemala, Belize, El Salvador, Honduras, Nicaragua and Costa Rica. The southernmost border of their distribution is found along the western coastal strip of South America. Agami herons have been observed in Panama between the months of January and June, suggesting dry season migration. (Cintra, 2012; "Herons and Bitterns (Ardeidae)", 2003; Garza-Torres, et al., 2003; Reynaud and Kushlan, 2004)

Habitat

Agami herons occupy inland wetland habitats. Forested swamps are particularly favored by the herons due to its diverse, wading-friendly foraging habitat, it also provides the trees and bushes necessary for roosting and nesting. More specifically, Agami herons dwell in dense tropical lowland forests, typically along the margins of small rivers, swamps and estuary streams. Studies have demonstrated that their distribution is most closely linked to the margins of isolated bodies of water. Agami herons are also known to use mangroves. ("Herons and Bitterns (Ardeidae)", 2003; Howell and Webb, 1995)

  • Range elevation
    2,600 (high) m
    ft
  • Average elevation
    300 m
    984.25 ft

Physical Description

These herons are medium-sized; they typically weigh between 0.1 and 4.5 kg and are 0.6 to 0.76 meters tall. Agami herons are short-statured and exhibit a crouched-like appearance. Their bill is rapier-like and is typically 13.9 cm in length, which represents one-fifth of their total body length. Agami herons have been characterized as having striking, dichromatic plumage. Adults have prominent, sickle-shaped plumage on each side of their head. Their abdominal region is chestnut-brown while their wings are dark teal, with brown streaks on both their ventral and dorsal surfaces. Their wings are broad, spanning 100 cm, with 9 to 11 primary feathers. Their tail feathers are short and light-brown in coloration. Males and females differ only slightly in their coloring and size, although males do tend to have more brilliantly colored plumage. Juveniles have darkened, cinnamon-striped abdominal plumage, which is reduced to chestnut-brown in adulthood. Juveniles also possess light blue feathers surrounding their crown. (Dittmann and Cardiff, 2009; "Herons and Bitterns (Ardeidae)", 2003; Garza-Torres, et al., 2003; Hancock and Kushlan, 1984; Hancock, 1999; Reynaud and Kushlan, 2004)

  • Range mass
    0.1 to 4.5 kg
    0.22 to 9.91 lb
  • Average mass
    2.5 kg
    5.51 lb
  • Range length
    0.60 to 0.76 m
    1.97 to 2.49 ft
  • Average length
    0.70 m
    2.30 ft
  • Range wingspan
    41 to 203 cm
    16.14 to 79.92 in
  • Average wingspan
    100 cm
    39.37 in

Reproduction

Agami herons are serially monogamous. While herons generally return to the same site to nest year after year, it is not known if Agami herons participate in life-long partnerships, or return to find new mates. They are known to nest in mixed or single species colonies, classifying them as social, colonial nesters. For social nesters, despite monogamous pairing, promiscuous mating behavior may be common. It is not known whether Agami herons participate in extra pair copulations, however, it is suspected. Males tend to arrive at colony sites to claim nesting territory. During the breeding season, males display wispy, light-blue crest feathers and broad light-blue plumes on the lower backside of their body, which they often puff out and shake to attract potential mates. During the mating display, males lift their head to a vertical position and bring it down abruptly in a bobbing fashion; this is often followed by snapping their bill. Later in the nesting season, this type of communication is used between mating pairs in social interaction and in mate recognition. Once pairs are established, both males and females work together to build nests. Males are largely responsible for defending the nest territory. (Dittmann and Cardiff, 2009; "Herons and Bitterns (Ardeidae)", 2003; Hancock, 1999)

Agami herons nest primarily in the wet season, between the months of June and September. Nests can be found in bushes and trees over water and under the dense cover of the canopy. Specific locations for nests include isolated clumps of mangroves, dead tree branches of drowned trees in artificial lakes, trees standing in water and bushes within marshes. Agami herons prefer to keep nests well hidden within terrestrial vegetation. Nests themselves average 15 cm in diameter and 8 cm in height and are characterized by loose, thick, platform twigs. Clutch sizes range from 2 to 4 light blue eggs. Little is known about their incubation period; however, the incubation time of other herons is approximately 26 days. Time to fledgling is approximately 2 to 3 weeks and time to independence is about 6 to 7 weeks. The exact age when sexual maturity is reached in Agami herons is not known, however, it is estimated to be between 2 to 3 years. ("Herons and Bitterns (Ardeidae)", 2003; Hancock and Kushlan, 1984; Marin, 1982; Reynaud and Kushlan, 2004)

  • Breeding interval
    Agami herons breed once yearly.
  • Breeding season
    Breeding occurs during the wet season, from June through September, this is the time of maximum annual rainfall.
  • Range eggs per season
    1 to 4
  • Average eggs per season
    2

Prior to fertilization, male herons participate in building nests, while building, males defend their nesting territory. Agami herons incubate and shade their eggs during daylight hours. Both parents take turns brooding the nest. The total brooding time ranges from 1 to 2 weeks. One parent forages for food while the other watches over the nest. Feeding birds leave and return to the nesting colony individually, and do so during the night. Research suggests that nesting Agami herons leave to feed in the swamps and savannas between the coastal mangrove forests and travel up to 100 km from their nest to feed. When returning to the nesting colony, adults make short, loud calls, and in response, chicks give a high-pitched answer; this is known as the "Chup" call. Incubation begins before the clutch is completed and young hatch at different times. The oldest chick dominates over the younger chicks in competition for food. ("Herons and Bitterns (Ardeidae)", 2003; Marin, 1982; Reynaud and Kushlan, 2004)

  • Parental Investment
  • altricial
  • male parental care
  • female parental care
  • pre-fertilization
    • protecting
      • male
  • 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

Little is known about the lifespan of Agami herons. It has been estimated that they live approximately 13 years, which is common for members of family Ardeidae (herons, egrets). Their lifespan in captivity has not been measured. The oldest documented individual lived 16 years. (Dittmann and Cardiff, 2009; Reynaud and Kushlan, 2004)

  • Range lifespan
    Status: wild
    16 (high) years
  • Typical lifespan
    Status: wild
    10 to 16 years

Behavior

Little is known about the behavior of Agami herons, apart from their mating behavior. However, they are often observed standing in a crouched position on banks, dykes, bushes or branches overhanging the water while foraging. They also have been documented walking slowly in shallow water at the edge of streams or ponds when hunting for fish. They rattle off a low-pitched alarm call when threatened. They spend most of their time, apart from nesting season, alone as solitary foragers. Due to the rare sightings of Agami herons, it has been hypothesized that when they are not foraging, they spend most of their time hidden in the canopies of trees. The solitary and evasive nature of Agami herons makes them difficult to observe from long distances. Their exact migratory patterns have yet to be documented; however, it has been proposed that they do not take part in long distance travel due to their ability to co-exist with other species of heron that lack their distinct bill and body morphology. ("Herons and Bitterns (Ardeidae)", 2003; Hancock, 1999; Reynaud and Kushlan, 2004)

Home Range

Male Agami herons are known to show territorial behavior when guarding a specific colonial area during mating season. The exact dimensions of the territory are not known, however, their home ranges may be relatively large due to their solitary foraging outside of mating season. (Hancock and Kushlan, 1984; Reynaud and Kushlan, 2004)

Communication and Perception

Agami herons are widely known for their distinct, low-pitched alarm call, which is used in response to threats. Their alarm call may also be used between mates as communication while nesting. In addition, males also use head-bobbing, bill clacking and calling as methods of attracting a mate. Research suggests that the pattern of such head-bobbing and bill clacking is used in mate to mate recognition while nesting and in defending nest territory. Upon arrival to the colony during nesting season, adults make a short, loud call, and in response, chicks make a high-pitched answer call. The characteristic social call of Agami herons is a low-pitched rattle called the "Gr" call. The "Gr" call has been characterized and described as a pig-like, low-pitched rattle. ("Herons and Bitterns (Ardeidae)", 2003; Reynaud and Kushlan, 2004)

Food Habits

Agami herons are specialized bank fishers. Their morphological adaptations have allowed them to effectively forage in shallow water on grassy shores. Their short legs and long neck give them the power to produce a long, lunging strike at prey items. They are solitary feeders, with individuals often scattered along water courses. With their long neck and bill, they are primarily piscivorous, feeding on a variety of fish. Agami herons are also known to employ a wading technique of foraging, which mixes standing still and slowly wading, usually in a deep crouch with the ventral feathers of their neck touching the water. Agami herons consume prey ranging between 2 to 20 cm. The majority of their prey consists of characins (Triportheus angulatus and Astyanax angulatus) which are surface-swimming fishes. Less commonly, they have also been known to consume cichlids (Aequindens). ("Herons and Bitterns (Ardeidae)", 2003; Willard, 1985)

  • Animal Foods
  • amphibians
  • fish
  • other marine invertebrates

Predation

Dichromatic plumage appears to help make Agami herons cryptic to predators; however, their method of solitary foraging may expose them to predation. Their predators include common black hawks and American crocodiles. (Caldwell, 1986)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Little is known of the role Agami herons play in the Neotropical ecosystem. Research suggests that all species belonging to the family Ardeidae contribute to the maintenance of fish diversity in streams by consuming highly abundant surface-feeding fish. Approximately 64.8% of all birds living in Guyana possess avian Hematazoa; however, specific parasites of Agami herons have yet to be analyzed. (Durrant, et al., 2006)

Economic Importance for Humans: Positive

The ways in which humans benefit from the ecosystem functions of Agami herons is unknown. However, humans have harvested herons' colorful plumes to sell at markets. Documents dating back to the 1800's suggest that plumes were harvested and made into expensive head pieces in tropical South American villages. In addition, eggs are harvested for food by some native populations. ("Herons and Bitterns (Ardeidae)", 2003; Gonzalez, 1999)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

There are no known negative economic impacts of Agami herons on humans.

Conservation Status

Current threats to Agami herons include deforestation in the Amazon basin. Deforestation models predict that Agami herons will lose between 18.6 to 25.6% of their suitable habitat. Conservation activity at this time has not been specified, however, proposals have been made to conserve the herons' habitat and expand protected area networks to be more inclusive of IBAs (Important Bird Areas). Due to the exclusivity and hidden nature of Agami herons' habitat, conservationists are aiming to expand market pressures for responsible land management. Limiting the use of unsuitable land for agricultural ventures has been the main focus in maintaining the herons' habitat. (Garza-Torres, et al., 2003; Lees, 2011)

Other Comments

Herons date back to the Eocene Era, 60 to 38 million years ago. Herons are often not represented in the fossil record prior to the Pleistocene due to the slight structure of their skeletons. Agami herons, along with boat-billed herons (Cochlearius cochlearius) and tiger herons (Tigrisoma), are considered the remnants of the basal lineage of Ardeidae. Agami herons are currently recognized as the only representative of their subfamily. ("Herons and Bitterns (Ardeidae)", 2003)

Contributors

Wendy Forrest (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

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

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

female parental care

parental care is carried out by females

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

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.

nomadic

generally wanders from place to place, usually within a well-defined range.

oviparous

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

piscivore

an animal that mainly eats fish

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

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.

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

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

visual

uses sight to communicate

References

Gale, Cengage Learning. 2003. Herons and Bitterns (Ardeidae). Pp. "239-260" in M Hutchins, A Evans, J Jackson, D Kleiman, J Murphy, D Thoney, eds. Grizmek's Animal Life Encyclopedia, Vol. 8: Issue I, 2nd Edition. Detroit: Gale.

Caldwell, G. 1986. Predation as a Selective Force on Foraging Herons: Effects of Plumage Color and Flocking. The Auk, Volume 103, Issue 3: "494-505".

Cintra, R. 2012. Ecological Gradients Influencing Waterbird Communities in Black Water Lakes in the Anavilhanas Archipelago, Central Amazonia. International Journal of Ecology, Volume 1, Issue 1: "1-21".

Dittmann, D., S. Cardiff. 2009. Herons. Pp. 59-61 in T Harris, ed. National Geographic Complete Birds of the World, Vol. 1. Washington, D.C: The National Geographic Society.

Durrant, K., J. Beadell, F. Ishtiaq. 2006. Avian Hematozoa in South America: A Comparison of Temperate and Tropic Zones. Ornithological Monographs, Volume 60: "102".

Garza-Torres, H., R. Herrera-Herrera, G. Escalona-Segura, J. Vargas-Contreras, A. Navarro. 2003. New Bird Records from Tamaulipas, Mexico. The Southwestern Naturalist, Vol. 48, Issue 4: "707-710".

Gonzalez, J. 1999. Effects of Harvesting of Waterbirds and Their Eggs by Native People in the Northeastern Peruvian Amazon. Waterbirds, Volume 22, Issue 2: "217-224".

Hancock, J. 1999. Herons & Egrets Of The World: A Photographic Journey. San Diego: Academic Press.

Hancock, J., J. Kushlan. 1984. The Herons Handbook. London, England: Christopher Helm Publishers.

Howell, S., S. Webb. 1995. A Guide to the Birds of Mexico and Northern Central America. New York, New York: Oxford University Press.

Lees, A. 2011. Integrating Spatially Explicit Habitat Projections Into Extinction Risk Assessments: A Reassessment of Amazonian Avifauna Incorporating Projected Deforestation. Diversity and Distributions, Volume 18, Issue 3: "273-281".

Marin, M. 1982. Notes on the Breeding of the Chestnut-Bellied Heron (Agamia agami) in Venezuela. The Auk, 99, Issue 4: "784".

Reynaud, P., J. Kushlan. 2004. Nesting of the Agami Heron. Waterbirds: The International Journal of Waterbird Biology, Vol. 17, Issue 4: "308-311".

Willard, D. 1985. Comparative Ecology of Twenty-Two Tropical Piscivores. Orinthological Monographs, Vol. 36: "788-797".