Cuculidae contains three major groups in the Americas: tree cuckoos, ground cuckoos, and anis; another two groups are found in the Old World. Medium to large birds, unifying features include a short, stout, slightly decurved bill, and zygodactylous feet. Most are forest-dwelling, although a few live in drier habitats, such as the famous roadrunner. New World cuckoos apparently follow the Complex Basic Strategy, even those that are migratory or live in open environments. In cuckoos, the sequence of wing molt can be highly irregular, appearing to start in multiple points and proceeding forward or backward, skipping some feathers, but simultaneously growing others. Rohwer and Broms showed that Yellow-billed Cuckoo and Common Cuckoo molt primaries in three or four series and rectrices in two series, conceptually not all that different from a Staffelmauser replacement pattern but resulting in complete replacement. The juvenile plumage can be like adults, or dramatically different, depending on the species.