Rails Cranes and Relatives: Gruiformes

Sunbitterns, limpkins, sungrebes, kagus, and rails tend to be solitary, living alone. Some species are territorial, that is, individuals defend a territory against other members of the same species. Other Gruiformes, however, such as seriemas and mesites, are frequently found in male-female pairs. Finally, some species of bustards, trumpeters, and cranes occur in flocks and can be highly social.

Gruiforms vary from highly able fliers to flightless species. Many cranes, for example, carry out long migrations between their breeding grounds and wintering grounds. Other Gruiformes are reluctant to fly, and flightlessness has in fact evolved many times in the group, particularly among the rails.

Reproductive behavior also varies within the Gruiformes. Cranes are monogamous (muh-NAH-guh-mus)—that is, each male mates with a single female and both parents are involved in building the nest, incubating the eggs, and caring for the chicks once they hatch. In order to strengthen the bond between the pair, cranes engage in elaborate "dances" in which they leap, extend their wings, and bob their heads. Mated crane pairs also sing, or trumpet, together. Crane pairs typically stay together all year round, rather than just during the breeding season, and some mate for life. At the other extreme in reproductive behavior, bustard males mate with as many females as they can. Females build nests, incubate eggs, and raise young on their own, without assistance from the male.