Chalked-browed Mockingbirds

Quick Facts

• Scientific Name: Mimus saturninus
• Spanish Name: Calandria grande
• Family: Mimidae
• Known Nicknames: Calandria grande, Sabiá-do-campo, Chalk-browed Mockingbird
• Average Length: 23–26 cm / 9–10.2 in
• Average Weight: 55–73 g / 1.9–2.6 oz
• Wingspan: 33–36 cm / 13–14 in
• Key Feature: Broad whitish supercilium (eyebrow) and long, graduated tail with white tips
• Primary Diet: Omnivore (Insects, small invertebrates, and various fruits)
• Range: Central and Eastern South America, including Brazil, Bolivia, Paraguay, Uruguay, and Northern Argentina
• Habitat: Open country, savannas, scrublands, pastures, and urban parks
• Social Structure: Highly Social (often engaging in cooperative breeding and group foraging)
• Nesting/Breeding: Cup-shaped nest built in thorny bushes or low trees
• Statut de conservation : Préoccupation mineure (LC)
• Population Trend: Increasing

The Chalk-browed Mockingbird (*Mimus saturninus*) is a charismatic and highly vocal songbird native to the open landscapes and scrublands of South America. It is most easily identified by its striking white "eyebrow" or supercilium, which contrasts sharply against a dark eye-stripe and its elegant grayish-brown plumage. Known as a master of mimicry, this bird possesses an extraordinary vocal range, capable of flawlessly imitating the complex melodies of other species and even mechanical sounds found in its environment. Beyond its musical prowess and long, white-tipped tail, the Chalk-browed Mockingbird is distinguished by its bold, territorial personality and a fascinating social structure, often practicing cooperative breeding where older offspring remain with the family to help raise the next generation of chicks.

Faits amusants

Chalk-browed Mockingbirds are renowned for their "wing-flashing" behavior, where they rhythmically snap their wings open to startle insects out of the grass. Beyond their namesake white eyebrows, these birds are master vocal mimics capable of imitating dozens of other species and even mechanical noises like car alarms. They are also fierce defenders of their territory, often engaging in cooperative breeding where older siblings help raise the newest brood, and they are known to fearlessly dive-bomb animals many times their size to protect their nests.

Habitats et répartition

This bird is widely distributed across central and eastern South America, spanning from northeastern Brazil through Bolivia, Paraguay, and Uruguay to central Argentina. It thrives in various open and semi-open environments, particularly in savannas, grasslands, and scrubby woodlands such as the Cerrado and Chaco regions. Beyond natural landscapes, the species is highly adaptable and frequently inhabits human-altered areas, including pastures, suburban gardens, and urban parks. It prefers regions with scattered trees or bushes that provide elevated perches for singing and cover for nesting, generally avoiding dense, continuous forests.

Comportements & Reproduction

These birds are highly social and exhibit complex territorial behaviors, often living in small family groups throughout the year. They are renowned for their vocal mimicry and bold nature, frequently defending their territory against intruders with communal displays. A defining feature of their social structure is cooperative breeding, where non-breeding individuals—typically offspring from previous seasons—assist the dominant breeding pair. These helpers play a crucial role in territory defense and provide significant aid in feeding the nestlings, which enhances the overall survival rate of the brood. Reproduction typically occurs in open, cup-shaped nests built within dense shrubs or low trees. While the breeding pairs are generally monogamous, the cooperative nature of the group serves as a vital strategy to combat heavy brood parasitism from species like the Shiny Cowbird. Females lay three to four speckled eggs, and the entire social group participates in guarding the nest and nourishing the young. This communal effort allows the birds to maintain high reproductive success even in environments with high predation and competition.

Alimentation

The Chalked-browed Mockingbird is an opportunistic omnivore that maintains a highly diverse diet, primarily consisting of insects like beetles, grasshoppers, and caterpillars, as well as spiders and small vertebrates such as lizards or the eggs of other birds. Beyond animal matter, it consumes a significant amount of plant material, including various wild fruits, berries, and occasionally nectar from flowers. A fascinating aspect of its foraging strategy is its commensal relationship with large mammals; these birds are often seen following cattle or capybaras to snatch up insects flushed out of the grass by the larger animals' movements. Furthermore, they are notably bold and adaptable, frequently scavenging human food scraps in urban areas and even practicing kleptoparasitism by stealing food from other bird species to supplement their nutritional intake.

Couleurs

The Chalked-browed Mockingbird features brownish-grey upperparts with dark streaks and pale, whitish underparts. Its most distinctive mark is a broad, creamy-white "eyebrow" stripe contrasting with a dark eye-line. The wings and long tail are dusky with white tips and edges, providing a neutral, disruptive pattern that serves as effective camouflage in open scrub and savanna environments.

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