The Hoatzin is a unique bird of the South American river and marsh edge. Its chicks have claws on their wings, letting them scramble among the tree branches.
The colorful hoatzin has evolved a variety of highly unusual features that suit it to life in the permanently lush and leafy wetland of South America. The ungainly hoatzin does not need to fly far in search of food. In fact, its wings are more useful as stabilizers than for flight. The hoatzin’s small head supports a long, bristly and erect crest. Strong muscles operate both upper and lower parts of the bill, giving the bird a good grip on tough leaves. His wings are relatively large, but weak because of reduced flight muscles. The hoatzin uses its long, broad tail to counterbalance the enlarged crop. The tail is vital for a bird that prefers to scramble along branches rather than fly. The crop is muscular and large, making up about 13% of the total bodyweight. The hoatzin digests most of its food in the crop.
The hoatzin is found over a large part of South America, from Guyana and Brazil, west to Ecuador and Bolivia. Two factors affect the hoatzin’s range, anatomy and diet. With weak wings, the hoatzin is better at scrambling along branches than flying. Tough, tropical marshland vegetation, such as arum and the white mangrove, provides essential ingredients in its diet.
The hoatzin feeds mainly on arum and mangrove foliage. It picks at leaves with its beak, forms the pieces into a ball in its mouth and swallows the food in large chunks. The hoatzin’s crop, a storage cavity in the chest, is so powerfully muscled that leaves are broken down with ease. The crop is also divided into sections, both these factors help with digestion. Swallowed balls of leaves are ground into a fine mash in the crop before passing through the gizzard and small intestine to be digested.
The hoatzin is most active in the morning and the evening. It spends the hottest part of the day in dense foliage on a branch over the water. A poor flier, the hoatzin prefers to climb to the tops of low trees. With such a vantage point, the hoatzin can look out for danger or promising feeding areas. Hoatzins live in a colony of 10 to 20 members. Cooperative parents accompany young on their first awkward scrambles and spread their wings to screen a hide from predators.
Hoatzins breed through the year, breeding increases just before the rainy season and occurs in groups of two to six birds. Parents take turns sitting on the eggs. Newly hatched young are almost naked but soon grow a downy plumage. They stay in the nest for about 14 days, then start exploring, using their curious ability to swim. As the chick grows, it loses its wing claws, learns to fly and loses the ability to swim. It continues to use its spread wings for balance as it scrambles about.
The greatest threat to the hoatzin is that of the Amazon region in general. Widespread clearing of forests has reduced the hoatzin’s range, depriving local populations of their habitat.