The northern mockingbird, Mimus polyglottos, is only one of more than thirty species of birds referred to as mockingbirds. All live in the New World, but only the northern mockingbird occurs in the United States. Here it is represented by two subspecies, M. p. polyglottos (eastern United States) and M. p. leucopterus (western United States). In Texas the two subspecies intergrade in the Cross Timbers, the eastern part of the Edwards Plateau, the southern portion of the Blackland Prairie, and the central Coastal Plains. The northern mockingbird is robin-sized but is more slender than a robin. It is gray above and gray-white below and has conspicuous white wing patches and white outer tail feathers. The sexes appear almost identical and are rarely separable in the field, but the female is on the average smaller and has slightly darker outer tail feathers. Juvenile birds have brown hair spots on the underparts-a feature suggesting that the mockingbird's ancestors were spotted below, as are many of the other members of the family (Mimidae) that are living today. The western subspecies has a relatively shorter tail and is somewhat more buff-colored below. Partial and total albinism have been reported.
Northern mockingbirds occur throughout the United States except in the most northern regions. Their range extends south into Mexico and the West Indies. In Texas the species is a permanent resident from sea level to over 6,000 feet above sea level, and it is particularly common in gardens, parks, brushy areas, and along roadsides. It is rarely seen in deep forests or on prairies devoid of shrubs or small trees. It feeds on insects and other small animals, including lizards, snails, and sowbugs, as well as on fruits and berries. A unique behavior in mockingbirds is called wing-flashing. It is most commonly seen as the bird runs along the ground foraging for insects. The mockingbird stops abruptly and spreads both wings simultaneously, thus briefly exposing the white wing patches. It is generally thought that it does this to flush insects, but the behavior may have other functions as well; it is also seen in young birds when they are exposed to a situation new to them. Mockingbirds build their nests in trees, shrubs, and vines up to a height of fifty feet; they use twigs, leaves, horsehair, grass, cotton, string, and other materials. The three to six (usually four or five) eggs are twenty-four by eighteen millimeters in size and vary from blue to green, with reddish, brownish, or purplish spots. Both sexes build the nest and feed the young, but only the female incubates the eggs (for ten to thirteen days). A pair may remain mated for several years, and birds may live twelve years or longer in the wild.
The mockingbird's remarkable ability to imitate sounds is the basis for both its common and scientific name (Mimus, "mimic"; polyglottos, "many-tongued"). The song may continue for more than an hour without pause, and it is not unusual for singing to last through the night. The highly variable song contains not only sounds of other birds, but also such inanimate noises as those of whistles and sirens. Some of the sounds the birds imitate have a frequency higher than the human ear can detect. The male sings more than the female does, apparently to establish a territory and attract a mate. Mockingbirds are among the most capable defenders of their territory and frequently attack hawks and cats, which prey on them and their young. Northern populations are partially migratory, but Texas birds are presumed to migrate very little if at all. The northern mockingbird is the state bird of Arkansas, Florida, Mississippi, and Tennessee, as well as of Texas. It was adopted as the state bird of Texas in 1927, at the request of the Texas Federation of Women's Clubs. Until the early twentieth century it was a popular caged bird in Texas and the United States, as it is in parts of Mexico even today. It was also used to make bird pie in parts of the state. Like almost all nongame birds, the northern mockingbird has been strictly protected by state and federal laws for more than seventy years.