The Hoatzin (Opisthocomus hoazin)


Hoatzin chick climbing

Hoatzin chick climbing

I’m pretty excited to write about this week’s #BeakoftheWeek! The hoatzin, or stinkbird as it is endearingly known (due to a lovely stench it emits from its fermenting guts), is one of the most evolutionarily distinct birds in existence (lying in third, behind only the oilbird and cuckoo-roller) .  Check out this cool paper for more information.

It is the only member of the Opisthocomidae family, and ever since discovering this quirky creature whilst watching the life of birds I’ve been a big fan.  If you check out the gif to the left you’ll notice some pretty strange behaviour…

Their chicks have claws on their wings, unique in Aves, and they use them until their wings are strong enough to fly/ support them.  The presence of these claws historically led to people believing they were pre-historic, although I am of the belief that the shoebill has got to take the prize for looking like it should have walked with the dinosaurs.  I couldn’t reference Sir David Attenborough without a link to some of his work, so here he is talking about hoatzin claws in the life of birds.  Here is an interesting article on the evolution of wings.

Sir David's Life of Birds

Sir David’s Life of Birds

During the non-breeding season they will live in groups of up to 100, that is a lot of Hoatzin.  They are cooperative breeders, sometimes in groups with up to 6 helpers, which are known to help with nest building, care of chicks and some incubation duties.  The usual clutch size is two.  The chicks leave the nest after about 2-3 weeks, but are dependent upon adults for up to 3 months.  They vigorously defend their territory during the breeding season.

So, where does that stinkbird alias come from? They have been likened to flying cows due to their diet consists more or less entirely of leaves, which leads to their gut bacteria creating quite the smell when they break it down.  The large crop needed for food fermentation comes at a cost to flight ability, as it reduces sternum size, affecting flight muscles.  They are rarely seen to take to the wing because of this, but this does not mean they are unable to.  This video, although having an annoying high pitched ringing, does show one flying a short distance if you needed to see it to believe it.

Hoatzins chilling out. PC

Hoatzins chilling out. PC

Predation is the primary reason for nest failure, with nests being preyed on by many creatures including: wedge-capped capuchin monkeys (Cebus olivaceus), tiger rat snakes (Spilotes pullatus) and toucans.  They nest over water alongside lakes and slow-moving rivers in trees and bushes, which allows their young, which are able to swim, to drop into the water to escape predators.

Endemic to the Americas, they are a widespread across in the lowlands of northern South America and the Amazon rainforest. Unfortunately population size is unknown, but they are described as common and easy to spot due to their behaviour, and probably their stench.  Could be easy to tick these off the list if you get to South America then!  They are described as of least concern by the IUCN red list, even if their population is in decline.

Once again, I recommend heading over to Xeno canto to get more of a feeling of where this bird lives and what it sounds like.



IUCN of least concern The IUCN Red List of Threatened Species. Version 2014.3. <>. Downloaded on 07 May 2015.

Billerman, Shawn. 2012. Hoatzin (Opisthocomus hoazin), Neotropical Birds Online (T. S. Schulenberg, Editor). Ithaca: Cornell Lab of Ornithology; retrieved from Neotropical Birds Online:

BirdLife International (2015) Species factsheet: Opisthocomus hoazin. Downloaded from on 07/05/2015.

Thomas, B.T., Kirwan, G.M. & Sharpe, C.J. (2014). Hoatzin (Opisthocomus hoazin). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) (2014). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from on 12 May 2015).

Images and videos

Hoatzin (Opisthocomus hoazin)” by Scott Bowers is licensed under CC BY 3.0

TheHoatzin’s channel. 2012. Hoatzin claws. [Online]. [10/05/2015]. Available from: