Northern mockingbird

Appearance

The northern mockingbird is a medium-sized mimid that has long legs and tail. Males and females look alike. Its upper parts are colored gray, while its underparts have a white or whitish-gray color. It has parallel wing bars on the half of the wings connected near the white patch giving it a distinctive appearance in flight.

The black central rectrices and typical white lateral rectrices are also noticeable in flight. The iris is usually a light green-yellow or a yellow, but there have been instances of an orange color. The bill is black with a brownish black appearance at the base. The juvenile appearance is marked by its streaks on its back, distinguished spots and streaks on its chest, and a gray or grayish-green iris.

Northern mockingbirds measure from 20.5 to 28 cm including a tail almost as long as its body. The wingspan can range from 31–38 cm and body mass is from 40–58 g. Males tend to be slightly larger than females.

Among standard measurements, the wing chord is 10 to 12 cm, the tail is 10 to 13.4 cm, the culmen is 1.6 to 1.9 cm and the tarsus is 2.9 to 3.4 cm.

The northern mockingbird's lifespan is observed to be up to 8 years, but captive birds can live up to 20 years.

Distribution

The mockingbird's breeding range is from Maritime provinces of Canada westwards to British Columbia, practically the entire Continental United States south of the northern Plains states and Pacific northwest, the Greater Antilles, and the majority of Mexico to eastern Oaxaca and Veracruz.

The mockingbird is generally a year-round resident of its range, but the birds that live in the northern portion of its range have been noted further south during the winter season. Sightings of the mockingbird have also been recorded in Hawaii, southeastern Alaska, and twice as transatlantic vagrants in Britain. The mockingbird is thought to be at least partly migratory in the northern portions of its range, but the migratory behavior is not well understood.

Habitat

The mockingbird's habitat varies by location, but it prefers open areas with sparse vegetation. In the eastern regions, suburban and urban areas such as parks and gardens are frequent residential areas. It has an affinity for mowed lawns with shrubs within proximity for shade and nesting. In western regions, desert scrub and chaparral are among its preferred habitats.

When foraging for food, it prefers short grass. This bird does not nest in densely forested areas, and generally resides in the same habitats year round.The northern mockingbird is a species that is found in both urban and rural habitats. There are now more northern mockingbirds living in urban habitats than non-urban environments, so they are consequently known as an urban-positive species.

Reproduction

Both the male and female of the species reach sexual maturity after one year of life. The breeding season occurs in the spring and early summer. The males arrive before the beginning of the season to establish their territories. The males use a series of courtship displays to attract the females to their sites. They run around the area either to showcase their territory to the females or to pursue the females. The males also engage in flight to showcase their wings. They sing and call as they perform all of these displays. 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.

Both the male and female are involved in the nest building. The male does most of the work, while the female perches on the shrub or tree where the nest is being built to watch for predators. The nest is built approximately three to ten feet above the ground. The outer part of the nest is composed of twigs, while the inner part is lined with grasses, dead leaves, moss, or artificial fibers. The eggs are a light blue or greenish color and speckled with dots. The female lays three to five eggs, and she incubates them for nearly two weeks. Once the eggs are hatched, both the male and female will feed the chicks.

The birds aggressively defend their nests and surrounding areas against other birds and animals. When a predator is persistent, mockingbirds from neighboring territories may be summoned by distinct calls to join the defense. Other birds may gather to watch as the mockingbirds drive away the intruder. In addition to harassing domestic cats and dogs that they consider a threat, mockingbirds will at times target humans. The birds are bold, and will attack much larger birds, even hawks. One incident in Tulsa, Oklahoma involving a postal carrier resulted in the distribution of a warning letter to residents.

The northern mockingbird pairs hatch about two to four broods a year. In one breeding attempt, the northern mockingbird lays an average of four eggs. They are pale blue or greenish white with red or brown blotches, and measure about 25 by 18 millimetres. They hatch after about 11 to 14 days of incubation by the female. After about 10 to 15 days of life, the offspring become independent.

Food

The northern mockingbird is an omnivore. The birds' diet consists of arthropods, earthworms, berries, fruits, seeds, and occasionally lizards. Mockingbirds can drink from puddles, river and lake edges, or dew and rain droplets that amass onto plants. Adult mockingbirds also have been seen drinking sap from the cuts on recently pruned trees.

Its diet heavily consists of animal prey during the breeding season, but takes a drastic shift to fruits during the fall and winter. The drive for fruits amid winter has been noted for the geographic expansion of the mockingbird, and in particular, the fruit of "Rosa multiflora", a favorite of the birds, is a possible link. Mockingbirds also eat garden fruits such as tomatoes, apples, and berries.

These birds forage on the ground or in vegetation; they also fly down from a perch to capture food. While foraging, they frequently spread their wings in a peculiar two-step motion to display the white patches. There is disagreement among ornithologists over the purpose of this behavior, with hypotheses ranging from deceleration to intimidation of predators or prey.

Predators

Adult mockingbirds can fall victim to birds of prey such as the great horned owl, screech owl and sharp-shinned hawk, though their tenacious behavior makes them less likely to be captured. Scrub-jays also have killed and eaten mockingbirds. Snakes rarely capture incubating females. Fledgelings have been prey to domestic cats, red-tailed hawks, and crows. Eggs and nestlings are consumed by blue jays, fish crows and American crows, red-tailed hawks, swallow-tailed kites, snakes, squirrels, and cats. Blowfly larvae and "Haemoproteus" have been found in Florida and Arizona populations, respectively.

Winter storms limit the expansion of mockingbirds in their range. The storms have played a role in the declining of the populations in Ohio, Michigan, Minnesota and likely in Quebec. Dry seasons also affect the mockingbird populations in Arizona.