Wild Things: Northern mockingbird (Mimus polyglottos)
This delightful songbird is 8-10” in length and has a wingspan just over a foot across. The coloring is rather inconspicuous: a white belly and light gray breast, gray back and head, and darker wings with white wing patches and outer tail feathers. But the drab appearance belies the amazing range of vocalizations the bird produces. Mockingbirds are mimics and are able to learn and reproduce the calls of other birds, as well as other sounds in their environment, such as the barking of dogs, cat mews, insect sounds, and even mechanical noises. They enlarge their vocal repertoire during their lives and may collect as many as 200 different songs. The scientific name makes reference to this vocal ability, polyglottos being Latin for “many tongues.” Both males and females sing, though the female's song is quieter than the male's. The song repertoire is thought to function in sexual selection, whereby a female may choose a mate based on the extent and variety of his singing ability, this skill presumably providing evidence of his vigor.
Males are also very energetic when singing to announce their territory ownership and attract a mate. They will often fly up off a perch and back again over and over again while singing. They also commonly stop while foraging on the ground and spread the wings, displaying white wing patches. Males will actively chase other birds, mammals, even people that venture too close to their nests. They will even defend preferred feeding sites. Experiments have shown that mockingbirds are able to recognize individual humans, attacking researchers who have previously come near a nest, but at the same time avoiding other unfamiliar people.
The Northern mockingbird is a common sight where it occurs across the southern U.S. and up into the upper Midwest and eastern seaboard states. It favors brushy forest edges with open ground nearby, riparian thickets, and croplands, but is also comfortable in urban settings around lawns, gardens, and other open areas. The diet is omnivorous, being about evenly divided between insects and a wide range of other invertebrates in spring and summer, then transitioning to fruits and berries in fall and winter.
Mockingbirds are year-round residents where they occur, though some northern populations may move southward in very cold winters. The Northern mockingbird's life span in the wild is about 8 years. The oldest individual identified by banding was in Texas and was over 14 years old.
Mockingbirds may produce 2-3 broods per season. The altricial chicks leave the nest after about 2 weeks and are fed by parents until they are able to forage on their own. As a result of the multiple broods each season, mockingbirds are prolific breeders. A female may produce as many as 25 eggs per season.
The affection generated by this familiar songster is evidenced by the fact that the Northern mockingbird is the state bird in five states: Texas, Arkansas, Mississippi, Tennessee, and Florida.
The Audubon Society reports that the Northern mockingbird population is stable and even expanding in some areas. Climatic warming is not predicted to seriously affect mockingbird populations.