The green-headed hillstar (Oreotrochilus stolzmanni) is a species of hummingbird found in the Andes of southern Ecuador and northern and central Peru. It is one of 6 species in the genus Oreotrochilus, and can be distinguished from its relatives by subtle differences in plumage coloration. The green-headed hillstar received its name due to its bronze and green crown and gorget of bright emerald green plumage. The species was first discovered by English ornithologist Osbert Salvin in 1895 and named after Polish ornithologist Jean Stanislaus Stolzmann.
Hillstars of this genus are distinct among the hummingbird family Trochilidae because of their preference for high-elevation environments, and the development of many behavioral and physiological adaptations in order to survive the cold climate of the high Andes.
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal",...
In zoology, a nectarivore is an animal that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of the sugar-...
Te
TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
Oviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
A territory is a sociographical area that which an animal consistently defends against the conspecific competition (or, occasionally, against anima...
Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables...
No
Not a migrantAnimals that do not make seasonal movements and stay in their native home ranges all year round are called not migrants or residents.
G
starts withThe green-headed hillstar is a species of South American hummingbird ranging in length from 12–13 cm and weighing between 7.9-8.4 g.
The green-headed hillstar is a sexually dimorphic species. The males are more brightly colored than females. Males have a bronzed-green posterior, including the forehead, crown, back, sides and rump. Their wings are a dark contrast to their back. The primaries and secondaries are typically a dark black/brown and green. Their tail's central rectrices are a soft bronze and their wide, blunt ended outer rectrices are nearly white. On their anterior, they have a metallic emerald green gorget that may appear bronze or blue in certain angles. Their underparts are white with a black streak down the center. At certain angles, the gorget of the adult male will have a slight blue gleam. The females share a similar physique to males, primarily differing in gorget and tail feathers. Their gorgets are white with dotted lines of green to grey spots. Females also have darker tails than males. Their tails are green and black with white webbing along the base of the outer rectrices. The wings of adult males are larger than those of adult females by approximately 3.5mm. This is a common trait for species in the hillstar genus, excluding the wedge-tailed hillstar. Juveniles resemble adult females.
There is no significant difference in measurements to the Andean hillstar, Ecuadorian hillstar, black-breasted hillstar or blue-throated hillstar. It is believed this is due to the commonality of a high altitude, cold Andean climate with similar diets, which has stabilized measurements specifically of the size of the bill, wing and rectrices.
The green-headed hillstar is distributed across north and central Peru, and extends up to the southernmost portion of the Ecuadorian Andes. Its habitat includes rocky alpine grasslands, meadows, and scrublands populated by Puya and Polylepsis stands.
They are found at altitudes of 3,600 to 4,200 meters (11,800 to 13,800 ft) and are known to seasonally shift to lower elevations.
The species is often spotted either perched on rocks or Puya clusters or occasionally on the ground in clearings. Females are more commonly found in gorges and valleys with more densely packed flora as these are some of the best nesting areas for high rates of clutch survival. Males also inhabit these gorges and valleys, but frequently occupy the rocky, more barren areas as well.
Jimbura is the only region in Ecuador acknowledged to have an occurrence of the species. It is a location that produces the Chuquiraga plant, one of a few food sources for the species.
The green-headed hillstar is usually sighted alone or in pairs, except during night-time, when groups gather in crevices and caves along the mountainside to roost. It is thought that this roosting behaviour exists to combat very cold nights at such a high altitude and as a way to evade nocturnal predators.
Similar to other hummingbird species, the green-headed hillstar has one of the highest mass-specific metabolic rates of all homeothermic animals, and therefore must consume a large quantity of sugar everyday in order to sustain this high metabolism. To reduce the metabolic cost of energy during the night when they are not feeding, hummingbirds are one of the few bird species that enter a state of torpor, or deep sleep, to reduce their metabolic rate to 1/15 of its normal rate. Hillstar species, like the green-headed hillstar, have further developed these behavioural adaptations in order to live in the especially cold climate of the Andes. For example, on cold nights the green-headed hillstar enters a state of torpor and will sleep in sheltered places like cavities in rocks or caves, and often sleep nestled close together with several other hillstars in order to reduce heat loss from their bodies. Additionally, while hummingbirds are distinct for their ability to hover by producing power on both the forward and back wing beat, in order to save energy the green-headed hillstar rarely hovers and instead clings to flowers to feed on their nectar, as well as only flying short distances. These behaviors can help minimize the energy required to maintain their body temperature and metabolism, and reduce energy expenditure which helps them thrive in the cold, harsh climate of the Andes.
Like other hummingbirds, the green-headed hillstar is a specialized nectarivore, and feeds preferably on the nectar and pollen of Puya, Cacti, Chuquiraga, and Cajophora/Caiophora. They are also known to occasionally feed on flying insects mid-air using a hawking technique.
They tend to perch on flowers within 3 feet of the ground, and will occasionally come and rest on the ground.
Males are highly territorial of feeding grounds.
The green-headed hillstar is one of few hillstars that appears to have a mutualistic relationship with the Chuqiraga plant genus. an estimate of 91% of its range overlaps with that of the Chugiraga. This plant genus is reliant on northern hillstars for pollination.
Like most hummingbirds, the green-headed hillstar uses its long and protractible tongue to collect small amounts of nectar from flowers. Its long and thin bill is a morphological characteristic correlated with a diet of nectar and pollen.
The green-headed hillstar will begin breeding during its second year of life, with the breeding season usually starting in February and ending in June, though sometimes continuing into August. A cup-shaped nest is built out of plant fibers and moss in protective places like rock cavities, under overhangs, in roofs or houses, or inside old open buildings like barns. The female lays a clutch of two white eggs, and incubates them for 19 to 21 days. When the eggs hatch, the chicks are generally dark with two dorsal rows of grey natal down or plumulaceous feathers. Fledgings of these young birds occurs approximately 36 to 40 after hatching. Courtship in the green-headed hillstar is not well studied, but evidence suggests males display using various postures to enhance their iridescent green gorget, and this is display is accompanied by melodious twittering.
