For two centuries, an unusual bird had been kept in wrong company. The hoatzin of South America, the only bird species to have a ruminant digestive system like a cow, was placed in the order Galliformes which includes pheasants, chickens and other birds with heavy bodies.

However, a group of scientists led by S Blair Hedges of Pennsylvania State University, US, has provided the first significant genetic evidence that the bird is more closely related to the cuckoo. A proposal has naturally followed to move this bird to the cuckoo's order, the Cuculiformes (Science, Vo1270, No 5243).