Of the 9,000 or so species of birds officially known to us, well over half -some 5,500- are classified as perching birds. Perching birds comprise the order Passeriformes. The great majority of passeriformes are members of the suborder Oscines -the songbirds.
On each foot, perching birds have four toes, one of which points backward. This arrangement enables the bird to easily perch on everything from leaf stems to thick branches. Tendons in the feet help the bird to flex its toes and grasp its perch tightly. Any movement that threatens the bird's equilibrium will cause the feet to tighten their grip. This explains why perching birds do not fall off thin telephone wires -even when the creatures are asleep on a windy night.
Perching birds vary greatly in appearance. In size, they range from tiny wrens only 3 inches (7.6 centimeters) long to the lyrebirds, which may be more than 40 inches (100 centimeters) long -counting their 30-inch (75-centimeter)-long tail. Colorwise, some species -such as the Baltimore, or northern, oriole and the cock-of-the-rock -have brilliant plumage. Others, such as the wood warblers and the house sparrows, are dressed in dull-colored feathers.
The beaks vary, depending on the food eaten by the bird. For example, wrens have long, slender, slightly downcurved bills -ideal for picking insects off leaves. Cardinals have large, heavy bills adapted to crushing seeds. The strong bills of the drongos hook at the tip and are slightly notched -the better to hold insects captured while in flight.
Most songbird species can be recognized by their distinctive song or songs. A few, such as crows and jays, imitate the calls of other birds.
A number of different taxonomic systems are used by scientists to classify the Passeriformes. In general, the group is divided into more than 50 families; more than 40 of these families comprise the suborder Oscines -the songbirds. Members of the other families are sometimes called Suboscines.
