Since 1933, the official state bird of Tennessee has been the northern mockingbird (Mimus polyglottos), a species of bird in the taxonomical family Mimidae. The northern mockingbird is the only species of mockingbird commonly found in North America.
It is primarily known for its mimicking abilities, as is reflected in its scientific name which translates to “many-tongued mimic.” Northern mockingbirds not only copy the sound of other species of bird, but also those of common animals like cats dogs, crickets, frogs, and even artificial sounds like squeaky car tires, car alarms, and doorbells.
The northern mockingbird was first systematically described by Swedish biologist Carolus Linnaeus in 1758. Since its original classification, scientists have further divided the northern mockingbird into three subspecies, differentiated by geographical location. It is found all over the continental U.S., the maritime and southern regions of Canada, and the northern parts of Mexico. Further south, the northern mockingbird is replaced by its close cousin the tropical mockingbird.
Despite originating in rural areas, the past 40 years have seen an explosion of mockingbird populations in urban areas; so much so that it is currently estimated that more mockingbirds live in urban areas than non-urban areas. The northern mockingbird is also the state bird of Arkansas, Florida, Mississippi, and Texas. It was the former state bird of South Carolina as well.
Appearance/Anatomy Of The Tennessee State Bird
The northern mockingbird is a medium-sized bird with a long tail and long legs. Its upper body is a grayish color and its lower body typically is white or whitish grey. They have a characteristic striped pattern on their wings that give them a distinctive appearance during flight. They generally measure 20.5–28 cm, with a 30-38 cm wingspan and a bodyweight of 40-48 g. The tail is approximately the same size as the body, coming in at an average of 10-13.4 m. Their eye color ranges from yellow to orange and their beaks are black with a brownish hue near the base. Males tend to be slightly larger than females, but otherwise, northern mockingbirds are not sexually dimorphic.
Behavior/Life-Cycle Of The Tennessee State Bird
Northern mockingbirds are omnivorous and their main dietary constituents change according to the season and food availability. During their breeding seasons of the spring and summer, they mostly subsist on small prey like arthropods, insects, worms, and sometimes small invertebrates like lizards or frogs. During the fall and winter, they primarily consume a diet of fruit, nuts berries, While eating, they will often spread their wings out in a wide pattern, most likely to deter predators or other birds from eating their food.
Both males and females reach sexual maturity after about 1 year. Like many species of bird, northern mockingbirds display a complex mating ritual with elaborate dances and vocalizations. After initial courtship, males and females will jointly build a nest where the female lays her eggs, typically 3-5 at once. Both males and females aggressively defend their nests and will not hesitate to attack larger birds such as hawks. They can even call other nearby mockingbirds to assist in defense. Both food availability and temperature can affect how long it takes the eggs to hatch, the average incubation period of their eggs is 11-14 days.
Newborn northern mockingbirds are defenseless and essentially immobile, so they rely entirely on their parent for nourishment and defense for the first few weeks of their life. Generally, the newborn chicks will progress to a stage of independence after about 40 days. They have an average lifespan of 8-10 years in the wild and slightly longer for mockingbirds in captivity. Mockingbirds often remain monogamous though they are sometimes seen to engage in bigamy and polygamy.
The most distinguishing feature of northern mockingbirds is their capacities for mimicry. Northern mockingbirds have been observed to mimic a wide range calls of other birds such as the Carolina wren, eastern bluebird, tufted titmouse, house sparrow, and wood thrush. Northern mockingbirds have are also known to copy the sounds of dogs, cats, crickets, frogs, horses, and even artificial sounds like car alarms, radios, and doorbells. Domesticated mockingbirds, like parrots or corvids, have also been reported to mimic human speech, but normally only a few words and phrases.
It is thought that mockingbird vocalizations serve 3 primary evolutionary purposes: sexual selection, communication, and defense. There are 4 main recognized categories of mockingbird vocalizations: nest relief call, hew call, chatburst, and the begging call, but a single mockingbird can remember up to 200 distinct individual vocalizations. The hew call is used by both sexes, mainly for predation warning, mating, and nest building. Nest relief calls and the begging call are almost exclusively used by males for the purpose of requesting resources. The chatburst call consists of 2 distinct patterns, a shorter one that is used year round and a longer call used primarily in the fall.
Despite being brave and rather effective predators, adult northern mockingbirds face a number of predators of their own, mostly by larger birds like screech owls, horned owls, hawks, and eagles. Newborn northern mockingbirds are particularly vulnerable and face predation from other birds, squirrels, snakes, and cats. Mockingbird eggs can be susceptible to blowfly larvae and other parasites.
Recent years have seen a large influx of mockingbird populations into urban areas; so much so that it is now estimated that more northern mockingbirds live in urban areas than non-urban areas. They show a particularly robust ability to adapt to urban environments. They will adapt their schedules to match periodic events occurring in the city and they can learn to use artificial light sources for navigation. Their adaptability is due to their high intelligence. Studies show that northern mockingbirds have a remarkable memory, and they can even remember and recognize individual humans, even after not having seen them for a long time. They have also been shown to modify their calls to better suit the acoustic properties in the environment, a form of acoustic adaptation. For example, they will modulate their calls to be a lower frequency to better propagate in the concrete environment of urban centers.