Hooded visorbearer

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 Template:Birdgloss 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

File:MonographTrochi4Goul 0086.jpg

Hooded visorbearer (lithography by Henry Constantine Richter (1821–1902) based on a drawing by John Gould (1804–1881))

Rene Primevere Lesson first described the hooded visorbearer for science in 1838, using a specimen collected in Bahia, Brazil.Template:SfnTemplate:Sfn He named it Ornismya lumachella.Template:Sfn Five years later, Lesson moved it and four other species to his newly created genus Amazilis.Template:Sfn 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.Template:Sfn DNA studies have shown that the two Augastes hummingbirds are sister species, and that the genus is most closely related to Geoffroy's daggerbill.Template:Sfn

The genus name Augastes comes directly from the Ancient Greek augastes, meaning "radiant" or "light-giver".Template:Sfn 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).Template:Sfn 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.Template:Sfn

Description

The hooded visorbearer is a small hummingbird, measuring in length and weighing .Template:SfnTemplate:Sfn Its short, straight bill is black.Template:Sfn The species is moderately sexually dimorphic. The male is an iridescent bronzy-green color on the upperparts and underparts.Template:Sfn His forehead and throat are an iridescent golden-green with a narrow border of bluish-green at the lower edge of the throat.Template:SfnTemplate:Sfn The sides and Template:Birdgloss 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.Template:Sfn His tail is a deep bronzy-crimson.Template:Sfn The female's coloring is more subdued. She is more bronzy on her upperparts and underparts, and her head is green instead of black.Template:Sfn She has a gray face and the sides of her head are brown, rather than black.Template:Sfn 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.Template:Sfn The combination of head pattern and tail color is said to make this species "unmistakable" within its small natural range.Template:Sfn

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.Template:Sfn

Range and habitat

The hooded visorbearer is endemic to eastern Brazil.Template:Sfn Found only in the Chapada Diamantina region of Bahia, it is restricted to campo rupestre,Template:Sfn a high-elevation ecoregion that is characterized by poor soils, open vegetation, rocky outcrops and harsh climatic conditions.Template:Sfn Its occurs at elevations ranging from ,Template:SfnTemplate:Sfn and is considered to be one of South America's obligate grassland birds.Template:Sfn It is found in rocky, semi-arid areas with cactus and low shrubs on the summits of mountains and mesas.Template:SfnTemplate:Sfn

Behavior

Feeding

Like all hummingbirds, the hooded visorbearer feeds primarily on nectar, though it will also take insects. It typically forages low, often less than from the ground.Template:Sfn It is known to visit Vriesea flowers early in the day, while the flowers (which are primarily bat-pollinated) still hold some residual nectar.Template:Sfn

Breeding

File:Augastes lumachella.jpg

Nesting

Little is known of the breeding ecology of the hooded visorbearer. It builds its nest from cactus spines, usually about a metre (just over three feet) off the ground.Template:Sfn

Conservation and threats

For several decades in the 20th century, the species was thought to have gone extinct. Then, in 1961, Brazilian naturalist Augusto Ruschi led an expedition to an area where they had been collected in the past, and rediscovered them.Template:Sfn The International Union for Conservation of Nature now rates the hooded visorbearer as a near-threatened species, based primarily on its relatively small range.Template:Sfn The decline of suitable habitat in both size and quality is ongoing, primarily as a result of uncontrolled fires and climate change. Projections suggest that the visorbearer's range may shrink by as much as 90% by 2060 due to the effects of climage change.Template:Sfn The mining of gold, diamonds, quartz and manganese within its range detrimentally affects habitat, as does the conversion of natural areas to animal pasturage and human habitation.Template:Sfn Although its population has not been quantified, its numbers are thought to be declining.Template:Sfn

Relationship with humans

The hooded visorbearer is considered to be among the handful of birds in the Chapada Diamantina that prove particularly attractive to birdwatchers. Trails have been created in the Chapada Diamantina National Park to enable ecotourists to enter the habitat in which they are found.Template:Sfn

References

Sources

• Template:Cite iucn

External links

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