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Acanthorhynchus tenuirostriseastern spinebill

By Kyung Ah Park

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. (Beruldsen, 1980; Higgins, et al., 2001; McDonald, 1973)

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. (Beruldsen, 1980; Chan, et al., 2008; Ford, et al., 1988; Leishman, 2000)

  • Other Habitat Features
  • 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. (Ford and Pursey, 1982; Higgins, et al., 2001; McDonald, 1973)

  • Sexual Dimorphism
  • sexes alike
  • sexes colored or patterned differently
  • male more colorful
  • Average mass
    11 g
    0.39 oz
  • Range length
    13 to 16 cm
    5.12 to 6.30 in
  • Range wingspan
    18 to 23 cm
    7.09 to 9.06 in

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. (Higgins, et al., 2001)

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. (Collins, 2008; Higgins, et al., 2001)

  • Breeding interval
    Eastern spinebills can breed up to 5 times per season, with a 37 to 41 day interval between clutches.
  • Breeding season
    Eastern spinebills breed between August and December.
  • Range eggs per season
    1 to 4
  • Average eggs per season
    2
  • Average time to hatching
    14.4 days
  • Average fledging age
    13.7 days
  • Average time to independence
    3 weeks

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. (Higgins, et al., 2001)

  • Parental Investment
  • altricial
  • male 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). (Higgins, et al., 2001; Munro, 2003)

  • Range territory size
    20,000 to 30,000 m^2

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. (Higgins, et al., 2001)

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. (Higgins, et al., 2001)

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. (McGoldrick and Nally, 1998; Munro, 2003; Scoble and Clarke, 2006)

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. (Timewell and Nally, 2004)

  • 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. (Higgins, et al., 2001)

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. (Huryn, 1997; Lowther, 2007; Scoble and Clarke, 2006)

  • Ecosystem Impact
  • pollinates
Commensal/Parasitic Species

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. (Johnson, et al., 2010)

Economic Importance for Humans: Negative

There are no known adverse effects of Acanthorhynchus tenuirostris on humans. (McGoldrick and Nally, 1998)

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. (Higgins, et al., 2001)

Contributors

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

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nectarivore

an animal that mainly eats nectar from flowers

nomadic

generally wanders from place to place, usually within a well-defined range.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

References

Beruldsen, G. 1980. A field guide to nests & eggs of Australian eggs. National Library of Australia: Rigby (Alalaide).

Chan, K., H. Ford, S. Ambrose. 2008. Ecophysical Adaptations of the Eastern Spinebill Acanthorhyncus Tenuirostris To a High Altitude Winter Environment. Emu: CSIRO.

Collins, B. 2008. The Ecology of the Eastern Spinebill Acanthorhyncus Tenuirostris (Meliphagidae) At the New England National Park, North-eastern NSW. Emu: Department of Environmental Biology.

Ford, H., J. Pursey. 1982. Status and Feeding of the Eastern Spinebill Acanthorhynchus Tenuirostris At New England National Park Northeastern NSW. Emu: ROYAL AUSTRALASIAN ORNITHOL UN.

Ford, H., H. Bell, R. Nias, R. Noske. 1988. The Relationship Between Ecology and the Incidence of Cooperative Breeding in Australian Birds. Behavioral Ecology and Sociobiology, 22: 239-249.

Higgins, P., J. Peter, W. Steele. 2001. HANDBOOK OF AUSTRALIAN NEW ZEALAND AND ANTARCTIC BIRDS. Melbourne: Oxford University Press.

Huryn, V. 1997. Ecological Impacts of Introduced Honey Bees. The Quarterly Review of Biology, 72/3: 275-297.

Johnson, K., P. McQuillan, J. Kirkpatrick. 2010. Bird Pollination of the Climbing Heath Prionotes cerinthoides (Ericaceae). International Journal of Plant Species, 171/2: 147–157.

Keast, A. 1968. SEASONAL MOVEMENTS IN THE AUSTRALIAN HONEYEATERS (MELIPHAGIDAE) AND THEIR ECOLOGICAL SIGNIFICANCE. Royal Australasian Ornithologists Union: Emu.

Leishman, A. 2000. A LONG-TERM BANDING STUDY OF BIRDS IN A SPOTTED GUM FOREST NEAR CAMPBELLTOWN, NEW SOUTH WALES. Australian Bird Study Association, 24/1: 6-12.

Lowther, P. 2007. Host List of Avian Brood Parasites. Cuckoo Hosts, 13/1: 1-55.

McDonald, J. 1973. Birds of Australia. Wilson Ornithological Society: Wilson Orthological Society.

McGoldrick, J., M. Nally. 1998. Impact of flowering on bird community dynamics in some central Victorian eucalypt forests. Ecological Research, 13/2: 125-139.

Munro, U. 2003. Life History and Ecophysiological Adaptations to Migration in Australian Birds. Avian migration, 598/156: 141-154.

Paton, D. 2000. Disruption of Bird-Plant Pollination Systems in Southern Australia. Conservation Biology, 14/5: 1232-1234. Accessed January 18, 2010 at http://www.jstor.org/pss/2641769.

Pyke, G. 2006. The foraging behaviour of Australian honeyeaters: a review and some comparisons with hummingbirds. Austral Ecology, 5/4: 343-369.

Scoble, J., M. Clarke. 2006. Nectar Availability and Flower Choice by Eastern Spinebills Foragin On Mountain Correa. Animal behaviour, 72/6: 1387-1394.

Timewell, C., M. Nally. 2004. Diurnal foraging-mode shifts and food availability in nectarivore assemblages during winter. Austral Ecology, 29/3: 264-277.

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