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Anhinga anhinga
Anhinga / Snakebird
(Linnaeus, 1766)
Detailed Texts Multi-lang
The Anhinga (Anhinga anhinga) is a large, slender waterbird with a prehistoric appearance. Its anatomy is designed for stealthy underwater hunting. It possesses an extremely long, flexible neck ending in a small head with a sharp, dagger-like bill with serrated edges. Its tail is long and stiff, similar to a turkey's, which it uses as a rudder underwater. It exhibits marked sexual dimorphism: males are a glossy black with greenish sheen and beautiful silvery-white streaks on the back and wings; females share these streaked wings, but their head, neck, and chest are a soft cinnamon or pale brown. Unlike ducks, its plumage does not fully repel water, giving it a soaked appearance when it emerges from the water.
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Last modified by
Julia Trouin
Taxonomy
PhylumChordata
ClassAves
OrderSuliformes
FamilyAnhingidae
GenusAnhinga
Taxonomic Authority(Linnaeus, 1766)
Ecology & Status
Origin
Native
Population Trend
Stable
Breeding Season
Year Round
Trophic Role
Carnivore
Recent Sightings
Yes
Habitat Summary Multi-lang
It is a species strictly linked to freshwater and brackish wetlands with calm or slow-moving waters. It inhabits lagoons, swamps, estuaries, mangrove channels, and river margins bordered by forests or dead trees. It imperatively requires low branches, fallen logs, or protruding roots to perch and dry its wings. In Costa Rica, it is a common and very conspicuous bird in areas like Caño Negro National Wildlife Refuge, Palo Verde National Park, Tortuguero, and the Tempisque River basin, from sea level up to 600 meters in elevation.Behaviour Multi-lang
It is a strictly diurnal bird. It spends much of its time hunting slowly underwater, searching for fish hidden among submerged vegetation. Because its plumage becomes soaked, it loses heat quickly in the water. After hunting, it must imperatively seek a sunny perch (like a dead tree), where it will stand with its wings fully extended for hours. This iconic pose serves not only to dry the feathers so it can fly again but also to absorb solar radiation and thermoregulate its body temperature.Social Activity Multi-lang
They generally hunt solitarily to maintain stealth. However, they are social birds when roosting (sharing dead trees with cormorants and herons) and strongly gregarious for nesting, forming bustling colonies.Feeding Guild Multi-lang
Carnivore / Piscivore.Trophic Chain Details Multi-lang
Carnivore (Specialized piscivore). Its diet consists almost 90% of small to medium-sized, slow-moving fish (such as mojarras and cichlids), supplemented with amphibians, water snakes, crustaceans, and aquatic insects. Adults are hunted in the water by caimans and large crocodiles. Their nests are highly vulnerable to climbing snakes, raccoons, and birds of prey.Reproductive Behaviour Multi-lang
They are seasonally monogamous birds. They nest in colonies on tall trees or shrubs projecting directly over the water to hinder access to terrestrial predators. The male collects sticks and leafy branches which the female weaves to form a bulky platform nest. The female lays 2 to 5 (usually 4) greenish-white eggs. Both sexes share incubation (about 25-30 days). The chicks hatch naked and defenseless (altricial), soon developing a dense white down, and are fed by regurgitation of partially digested fish by their parents.Physical Measures
Length (cm)
85.0 - 95.0 cm
Weight (Grams)
1.00 kg - 1.35 kg
Offspring per cycle2 - 5
Sexual DimorphismYes
Lifespan
Sexual Maturity
24 Months
Gestation / Incubation
25 - 30
Lifespan Estimated
Males9 - 12 Years
Females9 - 12 Years
Sexual Dimorphism
Males Multi-lang
The male possesses glossy black body plumage with intense greenish sheen and a completely dark neck and head.
Females Multi-lang
The female is easily distinguished by having a light brown or pale cinnamon head, neck, and upper chest.
Evolutionary Adaptations Multi-lang
Neutral Buoyancy (Wettable Plumage): Unlike ducks, the Anhinga produces very little oil in its uropygial gland, and its feather structure allows water to penetrate to the skin. By becoming waterlogged and expelling trapped air, it achieves neutral buoyancy, allowing it to stalk fish silently underwater without the constant effort of swimming downward to keep from floating.
Cervical Harpoon Mechanism: Its neck vertebrae (specifically between the 8th and 9th) possess a highly specialized hinge-like joint. This allows it to retract its neck and shoot it forward with explosive speed, impaling fish with its closed bill as if it were a harpoon.
Main Threats Multi-lang
Water Pollution: As a top predator in the aquatic food chain, the Anhinga is highly susceptible to the bioaccumulation of agricultural pesticides and heavy metals that run off into wetlands and concentrate in fish.
Fishing Gear Entanglement: Discarded or lost nylon fishing lines and hooks in rivers and lagoons often entangle in their wings or bills while diving, causing death by starvation or drowning.
Interesting Facts Multi-lang
The Snake Illusion: It gets its name 'Snakebird' from its swimming style. Thanks to its neutral buoyancy, it submerges its entire body below the surface, leaving only its long, sinuous neck and head protruding, moving through the water with undulations that mimic a swimming snake.
Fish Tossing: Once it spears a fish underwater, it has a problem: it cannot swallow it while impaled. The bird must come to the surface, vigorously shake its head to dislodge the fish from its bill, toss it into the air, and skillfully catch it head-first to swallow it whole without the fins getting stuck in its throat.