Hoatzin

Opisthocomus hoazin

Smells terrible, can barely fly, and baby hoatzins have claws on their wings. Legendary weirdo.

Population: No precise global numeric count published; widespread and locally common/abundant across Amazon and Orinoco basin wetlands (extent of occurrence ~8.62 million km² across 9 countries per IUCN 2024 assessment). Population trend is DECREASING, not stable — IUCN's 2024 assessment cites an estimated 11-14% population reduction over three generations, tracking an 11% loss of tree cover within its range, though not severe enough to meet Vulnerable thresholds.
Habitat: Flooded (riparian) forests, mangrove swamps, and dense vegetation along slow-moving rivers, lakes, and streams
Fun fact: The Hoatzin ferments leaves in an enlarged, muscular crop using symbiotic bacteria — much like a cow's rumen — making it the smallest known animal to rely on foregut fermentation (at ~700g body weight) and the only bird species to digest food this way, which also gives it a manure-like odor that earns it the nickname "stinkbird."
Range: Amazon and Orinoco river basins of South America — confirmed via IUCN 2024 assessment as present in Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela, mostly below 500 m elevation
Diet: Almost entirely folivorous — young leaves, shoots, and buds of swamp and riverside plants (one Venezuelan study: ~82% leaves, 10% flowers, 8% fruit); over 50 plant species consumed
Size: 0.65 m
Lifespan: 8 years

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