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Animal of the Month

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?).

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