FEATURED ANIMAL : THE HOATZIN BIRD (Opisthocomus hoazin )
Here’s a bird to grab your imagination! It doesn’t sing, it hisses, hoots, and yelps. It can hardly fly.
It perches on trees over the water most of the day, digesting its “prey” – the leaves of more than fifty swamp
plants. It is not even very good at that – it stuffs its belly so full that it has evolved a callus on its breastbone
to prevent its tipping over into the water below. Is it a cuckoo? a chicken? No one is sure, so many
ornithologists have put it into its own order, Opisthocomiformes (remember that). The hoatzin is unique in
several ways. No other bird has a fermenting system to digest its food (most birds do not eat leaves, of
course), while the hoatzin has a very large crop, a pouch off the throat, to do so. The crop contains bacteria
which do the hoatzin’s food processing for it (it begins to look as though the hoatzin is the sloth of the bird
realm), albeit rather slowly. It takes almost two days for a chewed leaf to move out of its innards into its
bloodstream. It probably doesn’t matter to the hoatzin, but this has the effect of making its person (if one
may use the term) rather odoriferous, hence its nickname, “the stink bird.” It has an even more bizarre
feature. The young look “primitive,” with two claws on each wing, which enable these babies to climb back
into their nest after clawing their way out onto limbs or leaping into the water to escape predators (or falling,
in case they are careless or overeager). They are born naked, only later developing black down.
Hoatzins are neotropical birds, munching their way through life in the Amazon rain forests of South
America. They are not large, less than a kilo (about 2 pounds) in weight and about 2 feet in length. But you
couldn’t miss a hoatzin. It has a blue-skinned face, red eyes, a topknot of reddish feathers, and a copperybrown
body with an elongated, bronze-green tail ending in a white band. This bird nests over the water
(hence the need for the infantile claws), and lays two to three eggs annually. The young are cared for by both
parents, who fiercely defend their breeding territory and precarious nest. Aside from protection, the parents
provide the young with the essential species of crop bacteria by regurgitating a sticky substance, which
contains these bacteria, into the mouths of the babies. After fledging, young hoatzins generally remain near
home until suitable shoreline territory for a new home becomes available, which may take several years.
Despite its eccentricities, the hoatzin has been doing something right. From fossil evidence, it appears
that hoatzins – or their ancestors – have been on this planet for 20 million years. Although the population of
these birds appears to be declining, so far hoatzins look on track to continue so long as sufficient habitat
remains and hunting pressure is not too great. Thus its future is up to us (hoatzin stew or a cheap hamburger
concocted from Brazilian cattle living on what had been Amazon rain forest, anyone?).
