The Northern Mockingbird, Mimus polyglottos, is a common medium-sized songbird perhaps best known for its song. With its large repertoire of songs and capability of mimicking a variety of sounds and other species’ songs, these birds are musical almost to a fault. Laying awake on a summer night, you might be surprised to find out the symphony outside your window is the product of a single Northern Mockingbird.
The Northern Mockingbird is a medium-sized bird. Males tend to be slightly larger than females, but on average, Mockingbirds measure between 8” and just over 10” in length and weigh between 1.5 to 2oz. They have long, thin, black bills that curve slightly downward and small heads. Their wings, with spans measuring 12” to over 13.5”, are broad and rounded and short in comparison to their long tails and legs.
Northern Mockingbirds have bilaterally symmetrical coloration. Their overall gray-brown plumage is accented by two white wingbars on each wing, a large white patch on the underside of each wing (flashed during flight,) white outer tail feathers and a pale breast and stomach.1 Females may be identified by their tail feathers that tend to be darker than males and juveniles by the brown spots on their undersides.
The mockingbird’s most notable characteristic is its ability to perform as many as 39 songs and 50 call notes and mimic any number of sounds ranging from the songs of other birds, to dogs barking, sirens, squeaky gates, and pianos.2 They sing throughout the day and into the night (unmated males are known to produce the most songs, especially at night during a full moon,) and from February through August and September through early November (some males have two distinct sets of songs, one for each season.) Over the course of its lifetime, a mockingbird may learn as many as 200 songs. It is believed that females prefer the males with the greatest number of songs. Females sing significantly less than males and at a lower volume. Females produce most of their songs in the fall for territorial purposes. Males also sing to establish territories as well as to attract mates.
Northern Mockingbirds are solitary animals that are often found alone, but may sometimes in found in pairs. They are known to be territorial throughout the year, especially during their mating seasons. Male mockingbirds tend to chase away male intruders and females tend to show more aggression towards female intruders. In defense of their territory, a mockingbird will chase an intruder to the edge of their territory and face-off, flying around them, prancing, hopping, and flashing their wings. This display may escalate to a physical fight that includes pecking and clawing if an intruding bird persists. Mockingbirds have also been known to chase away other species, including dogs, cats and humans.3 Within their habitats, adult mockingbirds are vulnerable to screech owls, great horned owls, sharp-shinned hawks, and scrub jays. Crows, blue jays, squirrels and snakes prey upon their eggs and young. If a predator is spotted approaching a nest, an adult mockingbird will emit an alarm call, sometimes causing a mob of mockingbirds to form to drive away the threat.4
Mockingbirds are diurnal and spend their time conspicuously perched on tall vegetation, poles, fences, or wires. On the ground, mockingbirds move by walking, hopping or running with their tails cocked, while hunting for insects. To collect fruit or hanging food, they are able to hover in mid-air. They tend to have a leisurely flight style with flashy wing beats, but are known to sometimes dive from their perches with folded wings.5
Northern Mockingbirds are protected by the US Migratory Bird Treaty Act. It is estimated that there are 45,000,000 Northern Mockingbirds worldwide and this species is not considered to be at risk.6 Approximately 83% of Northern Mockingbirds are believed to live in the United States, 16% in Mexico, and 6% in Canada.7
Northern Mockingbirds are susceptible to a number of ectoparasites, such as fleas, mites, and blowfly larvae. In the wild, Northern Mockingbirds have a life expectancy of 8 years. In captivity they may live up to 20 years.
Northern Mockingbirds inhabit nearctic and oceanic habitats across the continental United States, in southern Canada, northern and central Mexico, and the Caribbean. They were introduced to Hawaii where they have experienced success. Northern Mockingbirds are a partially migratory species. Populations that breed in northern parts of the range tend to migrate south for colder months, while populations that breed in southern parts of the range tend to be non-migratory.8
Northern Mockingbirds can be found in a variety of habitats at low elevations, including brushy deserts, forest edges, suburbs, parks, and farmlands. They prefer habitats that include open grassy areas for foraging,9 shrubby vegetation, and high perches (such as trees, poles, etc.) Within their habitats, Northern Mockingbirds play a vital role in seed distribution and the maintenance of insect population.
Northern Mockingbirds are omnivores that forage on the ground or while perched in vegetation. Their diets are insect and animal heavy in the summer, consisting of ants, bees, wasps, spiders, grasshoppers, moths, beetles, and sometimes small lizards and crustaceans. During the fall and winter, they adapt their diets to include fruit and berries such as mulberries, raspberries, holly, brambles, figs, and grapes.10 Northern Mockingbirds source water from the edges of rivers, lakes, and puddles, collect dew from leaves, and have been known to drink sap from freshly trimmed trees.11
Northern Mockingbirds are typically monogamous and remain in breeding pairs for the duration of one mating season. Occasionally, mockingbirds may practice polygyny or bigamy or remain in a breeding pair for life. The spring and early summer mating seasons commence with males establishing their territories to attract females.12 Within their territories, males select several nesting sites and construct bulky, cup-like twig nests that are usually 3’ to 10’ off the ground (although these nests can be built at heights up to 60’.)13 After entering a male’s territory, a female is chased by the male, who performs songs, flight patterns and wing flashes in a showy display. By the end of the chase, the female will have been shown all the potential nesting sites within the territory and will choose one. Prior to laying her eggs, a female mockingbird lines the twig cup constructed by the male with grass, leaves, and sometimes bits of trash. Mating pairs will have two to four broods a year.14
Females lay between 2 to 6 eggs, which are pale blue or green with red or brown spots. The eggs are .8” to 1.1” long and .6” to .8” wide. The female incubates the eggs for 12 to 13 days. Chicks are born helpless, naked, blind, and covered in light grey down. Both females and males participate in feeding and caring for the chicks. After a nestling period of 12 to 13 days, the female mockingbird leaves the nest to lay her next brood in a new nest while the male remains with the fledglings, continuing to care for and feed them and teaching them to fly.15 The young are independent by 15 days old and reach sexual maturity by a year old. Northern Mockingbirds rarely reuse a nest.
There are three species of Cowbirds, Molothrus, that parasitize Northern Mockingbirds. They lay their eggs in a mockingbird’s nest, where the eggs will be incubated, hatched, and cared for by the mockingbirds. The cowbird chicks sometimes overcrowd the nest, resulting in the loss of mockingbird chicks.16
Notes of Interest
Mockingbirds were kept as caged novelties during the 19th century. Chicks were taken from nests or adults were trapped and sold for upwards of $50. This practice was so popular in cities such as New York, St. Louis, and Philadelphia that mockingbird populations nearly vanished from areas along the East Coast.17
According to the North American Breeding Bird Survery, Northern Mockingbird populations are on the decline. Between 1966 and 2010, this species experienced a 20% decrease.note
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