Acanthorhynchus tenuirostris

Geographic Range

Eastern spinebills are native to eastern and south-eastern Australia. They are widespread, ranging from east of the Great Divide to west of Carnarvon Gorge, passing through North Queensland. The range of eastern spinebills extends from the coast, inland to Boggabilla in the northwestern Plains Region. Acanthorhynchus tenuirostris is also found in Tasmania. These birds may migrate during cold months but they are usually within one region, depending on food source availability.

• Biogeographic Regions
• australian australian
  • native native

Habitat

Eastern spinebills mainly inhabit dense forest and woodlands with thick underbrush. They nest on a small tree or bush from a few to more than ten meters above the ground. They are common in low-altitude and near-coastal, dry heathland but they are sometimes present in the higher altitudes as well. They are occasionally found in rainforests, and less often in wet sclerophyll forest. Eastern spinebills are also common in urban gardens and parks. Eastern spinebills can be solitary or gregarious, and they show regular seasonal movements within a limited area depending on resource availability.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• rainforest rainforest
• scrub forest scrub forest

• Other Habitat Features
• urban urban

Physical Description

The sexual dimorphism of eastern spinebills is not significant. Male eastern spinebills have an overall glossy black body about 13 to 16 cm long. Upper tail and inner wings are gray. They feature a white throat and bib that extends to the belly, and have a smaller, brown bib that covers only the throat. The lower breast and belly are a light brown to yellow-brown color. Males have feet and legs that are either black or dark red-brown. Females are similar to males but have more of an olive-grayish appearance and less intense brown on the throat. Along with the light, yellow-brown belly, females often have white feathers dispersed throughout plumage. Unlike male spinebills, females have paler, grayish-pink feet and legs. Whereas the juveniles' eyes are black, the adults tend to have bright red eyes. Their wing span ranges from 18 to 23 cm and their long, thin bills range from 2 to 5 cm. The average body weight is 11 g although it increases during the winter months due to the storing of fat to conserve energy. Eastern spinebills go through two moulting stages sometime between early December and late April.

Acanthorhynchus tenuirostris can be distinguished from Acanthorhynchus superciliosus , or western spinebills, by differences in body size and appearance. A. superciliosus , slightly smaller than A. tenuirostris , has white supercilium and an overall appearance of olive-gray rather than black.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike
• sexes colored or patterned differently
• male more colorful

Reproduction

The exact mating system of eastern spinebills is unknown, but they are likely socially monogamous. A specific pair will nest and tend their brood, but individuals have been observed to make extra-pair copulations. To initiate a courtship flight, a male flies over to a female and either touches the female's tail with his bill or calls loudly. The display lasts for 15 to 30 seconds. They fly in an undulating pattern with the male pursuing the female. Sometimes the female turns around suddenly to face her pursuer and they hover briefly, touching each others' bills. In the end, they land near the location where they began. The courtship can last for over a week with feeding and resting occurring in between. There is no mate defense during courtship, so other male spinebills can come and initiate flight with the same female while the other male is resting or feeding.

• Mating System
• monogamous monogamous

The breeding season occurs from August to December. Both the male and female collect materials suitable for their nest, however only the female actually builds the nest. Females can lay up to 4 eggs, with an average of 2 eggs per clutch, and can lay up to 5 clutches per season. The approximate interval time between two clutches ranges from 37 to 41 days. The average incubation period last 14 days after which the nestlings are born, weighing around 8 g each. It takes an average of 14 days for young to fledge, and they become independent and begin foraging 8 days later. Information on when the young reach sexual maturity is not known, but once the young reach independence they leave the territory while the adults remain.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• oviparous oviparous

Incubation is primarily performed by female eastern spinebills, but males will occasionally assist. Both sexes remove fecal sacs when naked nestlings hatch from the eggs and feed the young every 5 to 10 minutes. Although the young occasionally are fed nectar, most of them are fed insects until they are capable of independently feeding on nectar. Nestlings are known to be very noisy while they are fed. After less than 2 weeks the parents encourage the young to fledge. The adults prepare for their subsequent nest 1 to 9 days after the young fledge. While the parents remain in the territory to make a new nest, juveniles leave the territory after being chased by their parents or voluntarily when they become independent.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female
  • protecting
    • male
    • female

Lifespan/Longevity

Currently there is no data available on the lifespan of Acanthorhynchus tenuirostris .

Behavior

Eastern spinebills are diurnal and are most active at mid-morning. They are usually seen alone or in a pair, and occasionally in groups of five. In patches with high nectar intensity, eastern spinebills are sometimes found mixed with parties of silvereyes ( Zosterops ), small warblers, and other honeyeater species. During winter months, small flocks move locally in response to food availability.

In mid-winter, males aggressively exclude smaller females from areas of rich nectar, leading females to have greater mortality. Due to their small body size, eastern spinebills are considered to be at the bottom of interspecific hierarchies. They retreat when they face conflicts with bigger birds such as New Holland honeyeaters ( Phylidonyris novaehollandiae ).

• Key Behaviors
• arboreal arboreal
• flies
• diurnal diurnal
• motile motile
• nomadic nomadic
• sedentary sedentary
• solitary solitary
• territorial territorial

Home Range

Home range varies depending on the availability of food source, but the breeding territory at Moruya, study site in Victori, Australia, was found to range from 2 to 3 hectares. Male spinebills defend breeding and feeding territories, and become most aggressive when they encounter conspecifics.

Communication and Perception

Eastern spinebills often produce high-pitched, rapid "pip" vocalizations. During courtship, pairs perform flight displays in which the male flies behind the female and they chase in an undulating motion. To initiate this courtship flight, a male will touch his beak to a female's tail. When feeding on flower nectar, eastern spinebills sing a piping territorial song to defend the flower. They raise feathers on their throat and crown and flick their tails 2 to 3 times per second if they feel threatened or when they are ready to fight. Eastern spinebills also perform broken-wing, distraction displays when their nestlings are threatened. Like all birds, eastern spinebills perceive their environment through audio, visual, tactile, and chemical stimuli.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Eastern spinebills are primarily nectar-feeders and use their highly-adapted, tubular beak to forage from tubular flowers. Their highly specialized beaks are hypothesized to be the result of a close co-evolution with the tubular flowers they feed upon. Eastern spinebills select flowers based on available nectar rather than size of the flower. Young are mainly fed on insects, differing from adults who depend on insects only during or prior to their breeding periods or when nectar availability decreases during winter.

These birds are most active during the day because the amount of nectar peaks at dawn and more insects are active at that time. Their nectar consumptions peaks in autumn, from August to October, mainly to store fat and increase their body mass to prepare for upcoming winter.

• Primary Diet
• herbivore herbivore
  • nectarivore nectarivore

• Animal Foods
• insects

• Plant Foods
• nectar

Predation

In public parks and gardens, feral cats and occasionally some domestic dogs kill these birds. Bird feeders that provide manufactured "nectar" can be detrimental to birds' health, due to the lack of thiamine in the refined sugar. Predation rate increases during the breeding season when helpless nestlings are vulnerable to attack. When adult birds sense a predator approaching, they perform broken-wing distraction displays and lure the predators away from the nest. If nestlings have fledged or are near fledging, they may flutter or explode from the nest when predators come near which often proves fatal.

Ecosystem Roles

Like all honeyeaters, eastern spinebills are very effective pollinators for nectar-producing plant species. While feeding on nectar, their heads often brush against the flower and collect pollen which is then transferred to the next flower they feed on. Due to their specialized bills, eastern spinebills forage from a limited group of flowering species, therefore reducing the amount of cross-pollination and resulting in very effective pollination. During winter or low nectar resources, eastern spinebills also prey on insects and likely impact their populations as well.

Several species of cuckoos including pallid cuckoos ( Cuculus pallidus ) and shining bronze-cuckoos ( Chrysococcyx lucidus ) are brood parasites known to use eastern spinebills as hosts. Brood parasitism can result in lower productivity for host species, as the parasitic young often eject other hatchlings out of the nest or out-compete them for food.

Eastern spinebills are also known to be hosts for some flower mites including Hattena cometis and H. floricola . The flower mites may negatively affect eastern spinebills by consuming nectar and therefore reducing food availability for spinebills.

• Ecosystem Impact
• pollinates

Economic Importance for Humans: Positive

Although humans are not affected directly, pollination by eastern spinebills allows for greater diversity of flowers not only in the wild but also in gardens and urban parks.

Economic Importance for Humans: Negative

There are no known adverse effects of Acanthorhynchus tenuirostris on humans.

Conservation Status

The increase in feral cat populations has led to population declines in eastern spinebills. Despite population declines of over 30% in recent years, the IUCN Red List labels the species as least concern.

Additional Links

Encyclopedia of Life

Contributors

Kyung Ah Park (author), University of Michigan-Ann Arbor, Phil Myers (editor), University of Michigan-Ann Arbor, Rachelle Sterling (editor), Special Projects.

References

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