Hoatzin

Hoatzin

We are delighted that Dr Hermann Josef Roth has taken on the sponsorship of the hoatzin.

The hoatzin(Opisthocomus hoazin), also known as the stinkbird, is a bird about 70 cm tall and the only species in its family Opisthocomidae. It is found in the northern half of South America, between the Andes and the Atlantic coast.

The external appearance of the hoatzin is unmistakable. It has a long and broad tail, a relatively long neck and a small head. The plumage on the upper side is dark brown while the wings and belly are reddish brown in colour. The neck and breast are beige in colour. Particularly striking is the small head with the bright red eyes, which are surrounded by a featherless and blue-coloured area. The hoatzin also has a thin, up to 8 cm long feather crest on its head, which is usually erect.

The habitat of the hoatzin is tropical rainforests in the Amazon and Orinoco region, in the immediate vicinity of rivers and streams. Here it spends most of its time in dense vegetation directly above the water. It makes no difference whether the water is fresh, salt or brackish. The hoatzin feeds exclusively on vegetation, mainly leaves and buds. Depending on the season, it also supplements its diet with flowers and fruit. To date, around 50 different plant species are known to feed on the hoatzin, some of which are toxic to other animals.

The breeding season of the hoatzin correlates with the rainy season in the Amazon region. The nest is built from dry branches in dense undergrowth directly above the water. The young from previous years often help the breeding couple to do this. The female lays between 2 and 4 eggs, which are incubated by all members of the group for around 30 days. The young leave the nest for the first time after 2-3 weeks and are ready to fledge after about 60 days. During this time, they are able to protect themselves from potential predators by jumping into the water. As they get older, the young lose the ability to swim and climb back up the trees.

The hoatzin has two special characteristics that are unique among birds living today. Firstly, the young have two claws on each wing until they are adults, which they can use for climbing and grasping after they have fled from an enemy into the water, for example. This is why the hoatzin is often associated with the prehistoric bird Archaeopteryx, which had three claws on each wing. On the other hand, the hoatzin is the only bird on earth in which digestion takes place mainly in the foregut instead of the stomach. Similar to ruminants. When full, the foregut can account for up to 25 % of the bird's total weight. It is mainly bacteria and other microorganisms that decompose the plant material, which the hoatzin itself would not be able to do. Its colloquial name "stink bird" probably comes from the odour that these bacteria produce during fermentation. As a consequence of the enormously enlarged foregut, the sternum and thus the flight muscles were greatly reduced to make room. As a result, the hoatzin can only fly very poorly and can only cover a maximum distance of 350 metres per flight. In addition, the enlargement of the foregut is accompanied by a shift in the centre of gravity. This is why adult hoatzins hardly use their legs for running or climbing, but rather crawl through the branches.

All these peculiarities are the reason why the relationship between the hoatzin and its relatives has not yet been definitively clarified and it is considered to be the only species of its genus or family. It can be assumed that the hoatzin split off from the other birds very early in the Earth's history and therefore has all these special characteristics.

Due to its extremely large distribution area in Amazonia, the Hoatzin's population is not yet endangered. The greatest threat to it is the deforestation of the rainforest. Due to its poor flying ability, it is unable to flee to unspoilt areas. According to the latest estimates, a fifth of its favoured habitat is destroyed every 20 years. This will reduce the number of wild specimens by around 25 % by 2036.