One of the most seen birds at Mamirauá Reserve, hoatzins have fingers with claws on their wings as young and have digestion similar to oxen!
Hoatzins (Opisthocomus hoazin) are among the birds with the most striking appearance among the 377 species that occur at Mamirauá Reserve. Some local guides say these animals have got this popular name because they appear to wear blue makeup around their eyes. For me, these animals have a more “rock star” vibe with these long, erect feathers on top of their heads, their red eyes highlighted and the predominant dark colors on their bodies.
Another special physical characteristic of these birds is the presence of fingers with claws on the wings of the young, but which are lost in adulthood. These claws are useful as they assist juveniles in locomotion. When threatened, the chicks can throw themselves from the suspended nests into the water below, swim to the vegetation on the banks and climb back when it is safe. The hoatzins won the title of “living fossils” for this appendage on the wings, also present in the found fossils of Archeopteryx, an extinct animal that would be the link between reptiles and the first birds.
A bird or an ox? 🤔
However, it is not just the look that differentiates the species, this bird is the only one in the world to have a digestive system similar to that of ruminants! Therefore, hoatzins have a folivorous diet, with cellulose digestion provided by symbiotic bacteria that live in their great necks. These are also responsible for the increase of the animal’s body mass and this reflects in the hoatzins’ low flight capacity (in fact they do not fly elegantly).
All these unique attributes mean that the hoatzins have won their own order (Opisthocomiformes) and a Family (Opisthocomidae), but in the past they have been associated with chickens (order Galliformes), Turks (family Musophagidae), pigeons (family Columbidae) , to cuckoos (order Cuculiformes), among others. The evolutionary history of the species Opisthocomus hoazin and its relationship with other groups of birds are not yet fully understood, requiring more studies and perhaps more fossil records, which is certainly much more difficult to obtain. Anyway, science never stopped in the face of difficulties and, therefore, the search continues (fortunately, for the eternal curious like me! 😀 ).
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Créditos (fotos e texto): Cynthia Lebrão
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