What's a Hoatzin?

Nancy Marie Brown
June 01, 1996

(Say it like "Watson.")

There's no other bird like a hoatzin. "It is the only bird that has a foregut for fermentation, like a cow's," explains Penn State biologist Blair Hedges. "It has bacteria like a cow's to help it digest cellulose and it has an enzyme like a cow's to extract nutrients from the bacteria."

Since 1776, when it was first described by science, birders haven't known what to make of this plump blue-faced South American beauty. Should it be lumped with pheasants and chickens as a galliform? (It's a heavy-bodied land bird.) Or is it closer to a cuckoo, which it recalls in plumage and markings?

To answer the question, Hedges and undergraduate student Melitta Simmons ignored both plumes and gut. They asked the hoatzin's genes. After sequencing two different types of DNA (mitochrondrial and nuclear), Hedges and Simmons can say without hesitation: Cuckoo. (Clarifies Hedges, "It's definitely related to the cuckoos, although it may not itself be a cuckoo. It's not even closely related to the galliforms.")

Why worry about the hoatzin? "I believe this study makes a good case that molecular genetic techniques reflect the true relationships between species better than morphological studies," Hedges says. Morphology—physical characteristics like body size and plumage—are the result of evolutionary adaptations to the environment, he explains, and can fool researchers about the relationships between species. Genes are more reliable. Knowing this, it's not surprising to learn that Hedges also works on the human family tree.

S. Blair Hedges, Ph.D., is assistant professor of biology in the Eberly College of Science, 208 Mueller Lab, University Park, PA 16802; 814-865-9991. Melitta D. Simmons is an undergraduate student in biology. Hedges' other colleagues on this project are Charles G. Sibley, author of Birds of the World, Marjon A.M. van Dijk of the University of Nijmegan, the Netherlands, and Wilfried W. deJong of the University of Amsterdam. Their work was funded by the National Science Foundation and a Penn State Center for Undergraduate Research Opportunities fellowship to Simmons. Reported by Barbara Kennedy.

Last Updated June 01, 1996