Chalk-browed Mockingbird
Mimus saturninus
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Quick Facts
- Scientific Name: Mimus saturninus
- Spanish Name: Zorzal cejiblanco
- Family: Mimidae
- Known Nicknames: Calandra, Sabiá-do-campo, Tem-tem
- Average Length: 25–28 cm / 9.8–11 in
- Average Weight: 60–80 g / 2.1–2.8 oz
- Wingspan: 35–40 cm / 13.8–15.7 in
- Key Feature: Prominent white eyebrow stripe above a dark eye-line
- Primary Diet: Omnivore
- Range: Central and eastern South America, from northern Brazil to northern Argentina
- Habitat: Open woodlands, savannas, scrublands, and urban areas
- Social Structure: Pairs or small family groups
- Nesting/Breeding: Open cup nest in a tree or shrub
- Conservation Status: Least Concern (LC)
- Population Trend: Stable
The Chalk-browed Mockingbird (*Mimus saturninus*) is a charismatic songbird of South America, easily identified by the bold, white stripe above its eye that resembles a chalk mark. With a sleek, gray-brown body, a long tail, and a pale belly, it looks like a larger, more robust version of its northern relatives. Its most special feature is a remarkable vocal repertoire: this bird is a master mimic, flawlessly imitating the calls of other birds, frogs, and even mechanical sounds, often weaving them into a complex, repetitive song from a prominent perch. Highly adaptable and boldly curious, it thrives in open woodlands, gardens, and urban areas from Brazil to Argentina, where it fearlessly defends its territory and nests from intruders, including humans.
Fun Facts
Despite its name, the Chalk-browed Mockingbird is a master of vocal deception, capable of flawlessly imitating not only other bird species but also the sounds of frogs, car alarms, and even chainsaws, using these calls to confuse predators and defend its territory. It exhibits a quirky "anting" behavior, rubbing ants—or sometimes even cigarette butts—through its feathers to harness the formic acid as a natural insecticide against parasites. This species is also fiercely territorial, known to dive-bomb humans, dogs, and even large hawks that venture too close to its nest, often targeting the back of the head with surprising accuracy.
Habitats & Distribution
The Chalk-browed Mockingbird inhabits a variety of open and semi-open environments, including savannas, scrublands, grasslands with scattered trees, pastures, agricultural areas, and urban parks and gardens. It avoids dense, humid forests, preferring edge habitats and areas with low, woody vegetation where it can forage on the ground or perch conspicuously. Its geographical range spans a large portion of central and eastern South America, from northeastern and central Brazil south through Bolivia, Paraguay, Uruguay, and into northern and central Argentina, extending as far south as the provinces of Buenos Aires and La Pampa.
Behaviours & Reproduction
The Chalk-browed Mockingbird is socially monogamous, with pairs forming bonds that often persist across multiple breeding seasons. Mating involves mutual displays, including duets and the male offering food to the female. The species exhibits cooperative breeding: offspring from previous broods frequently remain as helpers, assisting in nest defense, feeding the incubating female, and provisioning new chicks. Nests are bulky cups built in trees or shrubs, where the female lays 2–4 eggs. A unique strategy is their high rate of brood parasitism rejection; they aggressively mob potential parasites like the Shiny Cowbird and often eject foreign eggs, a behavior enhanced by learning from social group members. Both parents and helpers feed the young, which fledge after about 12–15 days but remain dependent for several more weeks.
Diet
The Chalk-browed Mockingbird is an opportunistic omnivore with a highly varied diet that shifts seasonally. During the breeding season, it consumes a large quantity of insects and other arthropods, such as beetles, grasshoppers, caterpillars, and spiders, providing essential protein for chicks. It also eats small fruits and berries from native and introduced plants, including those of the guava and palm trees, and is known to visit feeders for seeds and bread scraps. One of its most interesting dietary habits is its tendency to cache or hide food items, storing excess prey or fruit in crevices or under leaves to retrieve later. Additionally, it occasionally raids the nests of smaller birds to eat eggs or nestlings, and in urban areas, it has been observed picking ticks and parasites off the backs of capybaras and cattle, engaging in a form of commensal feeding.
Colors
The Chalk-browed Mockingbird is predominantly gray-brown above with a paler, whitish underbelly and a distinct, bold white supercilium (eyebrow) that gives it its name. Its wings and long tail are darker, with white wing patches and outer tail feathers that flash in flight. It lacks intricate camouflage, relying instead on its noisy, conspicuous behavior and open habitat.
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