Agamia agami

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.

• Biogeographic Regions
• neotropical neotropical
  • native native
• atlantic ocean atlantic ocean
  • native native

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.

• Habitat Regions
• temperate temperate
• tropical tropical
• freshwater freshwater

• Terrestrial Biomes
• chaparral chaparral
• scrub forest scrub forest

• Aquatic Biomes
• rivers and streams
• temporary pools
• brackish water brackish water

• Wetlands
• marsh marsh
• swamp swamp

• Other Habitat Features
• estuarine estuarine

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.

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

• Sexual Dimorphism
• sexes alike
• male more colorful
• ornamentation ornamentation

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.

• Mating System
• monogamous monogamous

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.

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

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.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female 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.

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.

• Key Behaviors
• arboreal arboreal
• flies
• diurnal diurnal
• motile motile
• nomadic nomadic
• solitary solitary
• territorial territorial

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.

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.

• Communication Channels
• acoustic acoustic

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

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 ).

• Primary Diet
• carnivore carnivore
  • piscivore piscivore

• 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 .

• Anti-predator Adaptations
• cryptic 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.

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.

• Positive Impacts
• food 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.

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.

Additional Links

Encyclopedia of Life

Contributors

Wendy Forrest (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, Leila Siciliano Martina (editor), Texas State University.

References

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

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Gale, Cengage Learning. 2003. Herons and Bitterns ( Ardeidae ). Pp. "239-260" in Grizmek's Animal Life Encyclopedia , Vol. 8: Issue I, 2nd Edition. Detroit: Gale.