A Bird with Hands and the Digestion of a Cow?

The Hoatzin, a species of tropical bird found in swamps and rain forests possesses an interesting adaption, Hoatzin chicks have a pair of small claws on the bend of their wings.

This feature is thought to have evolved as a predator avoidance strategy. When disturbed, nesting chicks can leap into the water, swim away, and when danger is gone they can haul themselves up branches and vegetation using their claws as grappling hooks.

Another interesting adaptation of Hoatzins is that they are leaf-eating folivores and posses a foregut fermenting system. The oesophagus and enlarged crop act as fermentation chambers, containing anaerobic bacteria that secrete enzymes able to break down the otherwise indigestible cellulose in the plant cell walls. These amazing birds digest their food more similarly to cattle than other birds, digesting very slowly with each meal taking up to 45 hours from ingestion to egestion.



An adult Hoatzin, also known as a stink bird. These birds have earned this nickname from the manure-like odour they emit, an unfortunate result of the aromatic compounds in the leaves they consume and the bacterial fermentation.