It is typically a permanent resident across much of its range, but northern mockingbirds may move farther south during inclement weather or prior to the onset of winter.

Studies have shown its ability to identify individual humans and treat them differently based on learned threat assessments.

[14] Sightings of the mockingbird have also been recorded in Hawaii (where it was introduced in the 1920s), southeastern Alaska,[18] and three times as transatlantic vagrants in Britain,[14] most recently in Exmouth, Devon, UK in February and March 2021.

In the 19th century, the range of the mockingbird expanded northward towards provinces such as Nova Scotia and Ontario and states such as Massachusetts, although the sightings were sporadic.

Within the first five decades of the 20th century, regions that received an influx of mockingbirds were Maine, Vermont, Ohio, Iowa, and New York.

In western states such as California, the population was restricted to the Lower Sonoran Desert regions but by the 1970s the mockingbird was residential in most counties.

[21] The birds' diet consists of arthropods (such as spiders, grasshoppers, wasps, bees, ants, beetles, butterflies, and caterpillars), earthworms, berries, fruits, seeds, and occasionally flowers, small crustaceans, and lizards (Anolis spp.).

[10][22][23][24] Mockingbirds can drink from puddles, river and lake edges, or dew and rain droplets that amass onto plants.

[14] Its diet heavily consists of animal prey during the breeding season, but takes a drastic shift to fruits during the fall and winter.

The species can remain monogamous for many years, but incidents of polygyny and bigamy have been reported to occur during a single bird's lifetime.

In addition to harassing domestic cats and dogs that they consider a threat,[12] mockingbirds will at times target humans.

One incident in Tulsa, Oklahoma involving a postal carrier resulted in the distribution of a warning letter to residents.

Since northern mockingbirds are abundant in urban environments, it is possible that the pollution and contamination in cities might affect sexual hormones and therefore play a role in offspring sex ratio.

[42] In these cases, these female breeders have the option of changing mates within a breeding season if the first male does not provide a high level of parental care, which includes feeding and nest defense.

[43] Northern mockingbirds are altricial, meaning that, when hatched, they are born relatively immobile and defenseless and therefore require nourishment for a certain duration from their parents.

[42] A recent study shows that both food availability and temperature affect the parental incubation of the eggs in northern mockingbirds.

Notable milestones, including the eyes opening, soft vocalizations, begging, and preening, began within the first six days of life.

Variation in begging and more compact movements such as perching, fear crouching, and stretching appeared by the ninth day.

Among the vocalizations it imitates are songs of the Carolina wren, northern cardinal, tufted titmouse, eastern towhee, house sparrow, wood thrush, and eastern bluebird, calls of the northern flicker and great crested flycatcher, jeers and pumphandles of the blue jay, and alarms, chups, and chirrs of the American robin.

[48][49] It imitates not only birds, but also other animals such as cats, dogs, frogs, and crickets and sounds from artificial items such as unoiled wheels and even car alarms.

[50] The northern mockingbird's mimicry is likely to serve as a form of sexual selection through which competition between males and female choice influence a bird's song repertoire size.

Male commencement of singing is in late January to February and continues into the summer and the establishing of territory into the fall.

Repertoire sizes ranged from 14 to 150 types in Texas, and two studies of mockingbirds in Florida rounded estimates to 134 and 200, approximately.

[14] The hew call is mainly used by both sexes for potential nest predators, conspecific chasing, and various interactions between mates.

[52] A similar paper published in 2023 had several participants exhibit varying levels of threatening behavior towards nesting mockingbirds.

[54] Biologists have long questioned how northern mockingbirds adapt to a novel environment in cities, and whether they fall into the typical ecological traps that are common for urban-dwelling birds.

[56] The adaptation of the mockingbird in urban habitats has led it to become more susceptible to lead poisoning in Baltimore and Washington, D.C. populations.

"[57] The Hunger Games franchise depicts "mockingjays," mockingbirds hybridized with jabberjays, genetically engineered birds which could memorize and repeat entire human conversations.

[63][64] In 1951, Patti Page, a popular vocalist, recorded "Mockin' Bird Hill", which was sold in 10" 78 RPM format.

The song reached #2 on Billboard's pop music chart and reflected gentle postwar values of the period.