40 Hoatzin or Stinkbird Facts That You May Not Know

The hoatzin is a South American bird with some strange features. It’s also called the reptile bird, the skunk bird, and the stinkbird. It's known for its unusual digestion method, an unpleasant smell, clumsy movement, and noisy behaviour. It's also famous for the claws on the wings of the young birds. Thankfully, it isn’t endangered, so we have time to investigate this bizarre bird and its life. In this article I list forty facts about the hoatzin that may be new to you.

1. The scientific name of the hoatzin is Opisthocomus hoazin. The species name is spelled differently from the common name of the bird.

2. The bird belongs to the family Opisthocomidae and the order Opisthocomiformes. It's the only member of its genus, family, and order.

3. The exact relationship of the hoatzin to other birds is uncertain. It seems to have had a very ancient origin.

4. Some evidence suggests that the bird originated in Europe. Fossils resembling bones of the hoatzin have been found on the continent. Younger fossils resembling the bird's bones have been found in Africa.

5. Researchers suggest that the birds travelled between continents on rafts of vegetation, as some mammals and reptiles are believed to have done. The continents were once joined together, but they separated long before the deposition of the hoatzin-like bones.

6. The hoatzin is about the size of a pheasant and may reach a length of twenty-six inches. Males and females look the same. The bird is quite colourful, especially when its wings are open.

7. The small head bears an untidy crest of long, spiky, and orange feathers. The crest causes some people to refer to the hoatzin as the "punk rock bird". The bird's neck is quite long.

8. The sides of the face are pale blue to sky blue in colour and have no feathers. The eyes are dark red.

9. The undersurface of the neck and body is buff or orange.

10. The wings are dark brown, grey, or black, except for the outer feathers, which are a lovely red to rusty-red colour. The sides of the body under the wings are orange or a shade that is referred to as "rufous-chestnut".

11. The tips of the dark tail feathers are buff to yellow in colour.

12. The hoatzin is found in the northern part of South America in many countries. The countries are shown on the map below and include:

• Bolivia
• Brazil
• Colombia
• Ecuador
• French Guiana
• Guyana
• Peru
• Suriname
• Venezuela

13. The bird is often seen perched on trees and shrubs in wetlands. It's found in areas with dense vegetation that are beside slow-moving rivers, lakes, and swamps.

14. The hoatzin is the national bird of Guyana.

15. Hoatzins are herbivores. They are said to be folivorous because they primarily eat leaves, though they eat some buds, flowers, and fruits as well.

16. The birds may accidentally ingest insects that are on the plants that they eat, but they don't deliberately seek these animals out.

17. The digestive tract of a bird contains extra chambers compared to that of a human, as shown in the illustration above. The crop is a pouch joined to the esophagus. The stomach consists of two sections: the proventriculus and the gizzard.

18. The hoatzin's lower esophagus and crop are unusually large. Bacterial fermentation of food in this area helps to break down food so that it can be absorbed. The process is similar to that in the rumen of a cow. The crop contains ridges that help to break the food up. The hoatzin is the only bird known to carry out foregut digestion.

19. The fermentation produces chemicals that can smell unpleasantly like dung to humans. They are released from the bird's gut, giving the animal the name of skunk bird or stinkbird.

20. There is some debate about how common or strong the bird's smell is. It may be variable in appearance or strength or it may be strongest for people who are particularly sensitive to the odour.

21. The birds appear to get most or all of the water that they need from the leaves that they eat because they are rarely seen drinking.

22. Hoatzins are very social animals and are sometimes seen in small or large groups.

23. They appear to feed early and late in the day. At other times they preen their feathers, sunbathe with open wings, or wash in puddles of rain trapped in the trees.

24. The birds are frequently detected by the sounds that they make. They are often very audible as they crash through the trees and vocalize.

25. Hoatzins produce several kinds of sounds, including grunts and croaks. The sounds enable the birds to remain in contact with each other. The birds also hiss when protecting their chicks.

26. The bird's sternum (breastbone) is reduced in size, apparently due to the space occupied by the enlarged crop. Flight muscles are attached to a bird's sternum. The small sternum of the hoatzin contributes to its weak ability to fly.

27. The birds spend most of their time climbing over branches instead of flying through the air. When they do fly, they travel only short distances.

28. Hoatzins exhibit a behaviour known as sternal perching. They rest their sternum on a branch as they perch.

29. Reproduction occurs during the rainy season.

30. Hoatzins aren't territorial during most of the year but become so during the breeding season. The breeding pair and several helpers defend the area around the nest.

31. In some cases, it's known that the helpers are offspring from the previous clutch. Hoatzins don't breed during their first year of life.

32. The birds nest in colonies. They defend the nest area from members of their own species and from predators.

33. The female creates a nest made of sticks in tree branches that overhang flooded land. A clutch consists of one to three eggs.

34. The eggs are incubated for around thirty-two days.

35. Researchers have discovered that the helpers aid in building the nest, incubating the eggs, and rearing the chicks.

36. The chicks have two claws on the front of each wing. These are eventually lost. They remind some people of the three claws on each wing of Archaeopteryx, a prehistoric animal with both dinosaur and bird-like features. There is no evidence that hoatzins are related to Archaeopteryx, though.

37. If an avian predator such as a hawk approaches the nest, the adults try to distract it. The claws help the chicks to climb over branches and hide from the predators.

38. The youngsters have another way to protect themselves. They drop from the nest into the water of the flooded land below. They can actually swim underwater and then find their nesting tree.

39. The young birds climb up the tree trunk with the aid of their claws until they reach the nest. Their escape mechanism can be helpful, though sometimes the water contains predators eager to eat the chicks.

40. For up to two months after hatching, the chicks feed on food regurgitated by an adult. When they swallow the regurgitated material, the chicks obtain the bacteria that they need for digesting plants.

The IUCN (International Union for Conservation of Nature) classifies the hoatzin in its "Least Concern" category. The bird is sometimes hunted for food, although it's said that its smell discourages this activity. In addition, its habitat is sometimes destroyed. In general, though, it appears to be doing okay at the moment. The IUCN does say that its population is decreasing, however, which could be a warning for the future.

Hoatzins are unusual birds and an interesting part of nature. The birds are hard to keep alive in captivity and haven't survived for long in this situation. There may be important facts about their biology still to be discovered. Hopefully we will soon learn more about their life and their origin.

Hoatzin information from the Cornell Lab of Ornithology

A misfit and a genetic mystery from the Audubon website

The hoatzin may have originated in Europe from the phys.org new service

An earlier article suggesting an African origin of the bird from phys.org

Opisthocomus hoazin facts from the Red List of the IUCN (International Union for Conservation of Nature)