The hooded visorbearer (Augastes lumachella) is a small species of hummingbird in the family Trochilidae. Endemic to the east Brazilian state of Bahia, it is found only at higher altitudes in the Chapada Diamantina region. The species is sexually dimorphic. The male is an iridescent bronzy-green overall, with black on his and the sides of his head. His forehead and throat are a glittering green shading to bluish-green at the lower edge and narrowly bordered by black. The female is bronzer, with a green crown and brown sides to her head. Her throat is less colorful than the male's, and she lacks iridescence on her forehead. Both sexes have crimson tails and a narrow white breast band, the male with a brilliantly iridescent golden-orange spot in the center, at the lower edge of his gorget.
It resides in the campo rupestre, an arid, high-elevation area characterized by rocky outcrops, poor soils, open habitats, and harsh climatic conditions. There, it feeds primarily on nectar, though it also takes insects. Its breeding ecology remains largely undescribed, though it is known to build its nest from cactus spines. The International Union for Conservation of Nature rates it as a near-threatened species, primarily because of the relatively small size of its range. It is threatened by habitat loss, brought about primarily by unregulated mining and the conversion of the campo to pastureland and human habitation. Climate change is projected to cause a major contraction of its range – perhaps by as much as 90%.
Taxonomy and systematics
Rene Primevere Lesson first described the hooded visorbearer for science in 1838, using a specimen collected in Bahia, Brazil. He named it Ornismya lumachella. Five years later, Lesson moved it and four other species to his newly created genus Amazilis. John Gould moved it again in 1849, when he created the genus Augastes for this species and the hyacinth visorbearer, another east Brazilian endemic. There are no subspecies. DNA studies have shown that the two Augastes hummingbirds are sister species, and that the genus is most closely related to Geoffroy's daggerbill.
The genus name Augastes comes directly from the Ancient Greek augastes, meaning "radiant" or "light-giver". The species name lumachella is an Italian word for fire marble – a dark limestone that contains fossilised shells; it is a diminutive of the word for snail (lumacha). Although the species name is sometimes written as lumachellus rather than lumachella, this is incorrect; because it is an Italian word (rather than a Latinized one), it is considered to be invariable.
Description
The hooded visorbearer is a small hummingbird, measuring in length and weighing . Its short, straight bill is black. The species is moderately sexually dimorphic. The male is an iridescent bronzy-green color on the upperparts and underparts. His forehead and throat are an iridescent golden-green with a narrow border of bluish-green at the lower edge of the throat. The sides and of his head are black, and a thin line of black borders his gorget. He has a narrow white breast band with a golden-orange spot in the center and purplish-brown wings. His tail is a deep bronzy-crimson. The female's coloring is more subdued. She is more bronzy on her upperparts and underparts, and her head is green instead of black. She has a gray face and the sides of her head are brown, rather than black. The green on her throat is less colorful and iridescent than that of the male's, with a stronger border of bluish-green at the lower edge; the color does not extend to her forehead. Immature birds are bronzy-green above and brown below, with a white throat speckled with green. Their tails are a coppery-bronze above and crimson below, less brilliantly-colored than those of adults. The combination of head pattern and tail color is said to make this species "unmistakable" within its small natural range.
Voice
The song of the hooded visorbearer is described as "nasal" and "dry". Transcribed as tru tweé tru zee, its short phrases are typically repeated more than three times in a row.
Range and habitat
The hooded visorbearer is endemic to eastern Brazil. Found only in the Chapada Diamantina region of Bahia, it is restricted to campo rupestre, a high-elevation ecoregion that is characterized by poor soils, open vegetation, rocky outcrops and harsh climatic conditions. Its occurs at elevations ranging from , and is considered to be one of South America's obligate grassland birds. It is found in rocky, semi-arid areas with cactus and low shrubs on the summits of mountains and mesas.