This Amazon bird digests leaves like a cow
The hoatzin of South America's Amazon and Orinoco swamps ferments foliage in an oversized crop, earning the nickname stinkbird. Chicks scramble on clawed wings, and Guyana claims the species as its national bird under the local name Canje pheasant.
Opisthocomus hoazin is the sole living member of its genus, family, and order. About 65 centimetres long, it shows a blue bare face, maroon eyes, and a spiky rufous crest over dark brown plumage tipped with a pale band on the long tail. It clambers through mangroves and riparian forest eating leaves, flowers, and fruit—one Venezuelan study found the diet about 82 percent leaves, 10 percent flowers, and 8 percent fruit across more than fifty plant species.
Front-gut bacteria ferment plant fibre so efficiently that up to about 70 percent may be digested, yet passage can take as long as 45 hours. The two-chambered crop is so large it crowds flight muscles; adults as light as about 700 grams are the smallest known animals with foregut fermentation, well below the roughly 3-kilogram lower limit typical for mammals. Serrated beaks cut leaves; methane exits by burping; locals avoid hunting the manure-scented bird except in hard times.
Nestlings carry two claws on each wing digit and can drop into water, swim, then climb back when hawks threaten. Comparisons to Archaeopteryx once tempted systematists, but modern work treats the claws as a secondary climbing adaptation also seen in turaco chicks. Genome studies still disagree on closest living relatives—one 2014 analysis linked the bird near cranes and plovers; a 2024 study placed it beside Phaethoquornithes—while genetic dating suggests a deep split around 64 to 70 million years ago.
Source: Hoatzin
