DNA tests identify hoatzin's cousins.

The closest relatives of the hoatzin, a blue-faced South American bird, are neither turkeys nor chickens, as many bird experts had assumed; they are cuckoos, a new study concludes. The finding shows that 220 years of research on the hoatzin was no wild-goose chase.

Since describing the bird, Opisthocomos hoazin, in 1776, ornithologists have had problems pinpointing its closest kin, as the hoatzin looks and acts so unlike other birds. It digests its food, for example, the way a cow does, in a chamber above its stomach (SN: 10/21/89, p.269).

Scientists have disagreed most recently over whether hoatzins are closer to cuckoos or to galliforms such as pheasants, chickens, and turkeys. Galliforms are among the most ancient of birds, while cuckoos appeared more recently.

S. Blair Hedges of Pennsylvania State University in University Park and his colleagues compared the DNA sequences of hoatzins and 13 other types of birds, they report in the Dec. 5 Proceedings of the National Academy of Sciences. The scientists examined DNA from one nuclear gene and two mitochondrial genes. They found that hoatzin DNA most closely resembles cuckoo DNA.

The scientists conclude, however, that the hoatzin belongs next to the cuckoo's nest, not in it, because the species' DNA and structural differences. For example, the cuckoo has two forward and two backward toes, while the hoatzin has three forward and one backward.

Indeed, the team recommends placing hoatzins in their own suborder, Opisthocomi, in the Cuculiformes order. All other members of the order, such as cuckoos, should then come under the suborder Cuculi.

The finding serves as an "eye-opening example of how molecular data can resolve phylogenetic relationships," says Hedges. Morphology "has tricked people for a long time."

Paul DeBenedictis of the State University of New York Health Science Center at Syracuse says that Hedges and his colleagues should have compared the hoatzin with a wider variety of birds. Still, he believes that "most ornithologists will accept what [the researchers] have to say," concerning the hoatzin's kin.