Bowerbird

This article is about the family of birds. For the band, see Bowerbirds (band).
Bowerbirds
Male satin bowerbird
Ptilonorhynchus violaceus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Suborder: Passeri
Family: Ptilonorhynchidae
GR Gray, 1841
Genera

Ailuroedus
Amblyornis
Chlamydera
Prionodura
Ptilonorhynchus
Scenopooetes
Sericulus

Bowerbirds /ˈbaʊərbɜːrd/ make up the bird family Ptilonorhynchidae. They are renowned for their unique courtship behaviour, where males build a structure and decorate it with sticks and brightly coloured objects in an attempt to attract a mate.

The family has 20 species in eight genera. These are medium to large-sized passerines, ranging from the golden bowerbird at 22 centimetres (8.7 in) and 70 grams (2.5 oz) to the great bowerbird at 40 centimetres (16 in) and 230 grams (8.1 oz). Their diet consists mainly of fruit but may also include insects (especially for nestlings), flowers, nectar and leaves in some species.[1] The satin[2] and spotted bowerbirds[3] are sometimes considered agricultural pests due to their habit of feeding on introduced fruit and vegetable crops and have occasionally been killed by affected orchardists.[3]

The bowerbirds have an Austro-Papuan distribution, with ten species endemic to New Guinea, eight endemic to Australia, and two found in both.[4] Although their distribution is centered on the tropical regions of New Guinea and northern Australia, some species extend into central, western, and southeastern Australia. They occupy a range of different habitats, including rainforest, eucalyptus and acacia forest, and shrublands.

Behaviour and ecology

The Ailuroedus catbirds are monogamous, with males raising chicks with their partner, but all other bowerbirds are polygynous, with the female building the nest and raising the young alone. These latter species are commonly dimorphic, with the female being more drab in color. Female bowerbirds build a nest by laying soft materials, such as leaves, ferns, and vine tendrils, on top of a loose foundation of sticks.

In courtship the male bowerbird will dance to the female in an attempt to attract her.

All Papuan bowerbirds lay one egg, while Australian species lay one to three with laying intervals of two days.[5][6] Bowerbird eggs are around twice as large as most passerines of similar size[7][8] – for instance eggs of the satin bowerbird weigh around 19 grams (0.67 oz) as against a calculated 10 grams (0.35 oz) for a passerine weighing 150 grams (5.3 oz).[4] Eggs hatch after 19 to 24 days, depending on the species[1] and are plain cream for catbirds and the tooth-billed bowerbird, but in other species possess brownish wavy lines similar to eggs of Australo-Papuan babblers. In accordance with their lengthy incubation periods, bowerbirds that lay more than one egg have asynchronous hatching, but siblicide has never been observed.[5]

Bowerbirds as a group have the longest life expectancy of any passerine family with significant banding studies. The two most studied species, the green catbird and satin bowerbird, have life expectancies of around eight to ten years[9] and one satin bowerbird has been known to live for twenty-six years.[10] For comparison, the common raven, the heaviest passerine species with significant banding records, has not been known to live longer than 21 years.[11]

The most notable characteristic of bowerbirds is their extraordinarily complex courtship and mating behaviour, where males build a bower to attract mates. There are two main types of bowers. One clade of bowerbirds build so-called maypole bowers, which are constructed by placing sticks around a sapling; in some species, these bowers have a hut-like roof. The other major bowerbuilding clade builds an avenue type-bower made of two walls of vertically placed sticks. In and around the bower, the male places a variety of brightly colored objects he has collected. These objects — usually different among each species — may include hundreds of shells, leaves, flowers, feathers, stones, berries, and even discarded plastic items, coins, nails, rifle shells, or pieces of glass. The males spend hours arranging this collection. Bowers within a species share a general form but do show significant variation, and the collection of objects reflects the biases of males of each species and its ability to procure items from the habitat, often stealing them from neighboring bowers. Several studies of different species have shown that colors of decorations males use on their bowers match the preferences of females.

Female satin bowerbird

Uy and collaborators have shown that mate-searching females commonly visit multiple bowers, often returning to the male several times, watching his elaborate courtship displays and inspecting the quality of the bower and tasting the paint the male has placed on the bower walls. Many females end up selecting the same male, and many under-performing males are left without copulations. Females mated with top-mating males tend to return to the male the next year and search less.

Bower of a great bowerbird

Ernest Thomas Gilliard suggested the transfer effect, in which he claimed that there is an inverse relationship between bower complexity and the brightness of plumage. Gilliard suggests that there is an evolutionary "transfer" of ornamentation in some species, from their plumage to their bowers, in order to reduce the visibility of the male and thereby its vulnerability to predation.[12] This hypothesis is not well supported because species with vastly different bower types have similar plumage. Others have suggested that the bower functioned initially as a device that benefits females by protecting them from forced copulations and thus giving them enhanced opportunity to choose males and benefits males by enhancing female willingness to visit the bower.[13] Evidence supporting this hypothesis comes from observations of Archbold's bowerbirds that have no true bower and have greatly modified their courtship so that the male is limited in his ability to mount the female without her cooperation. In toothbilled bowerbirds that have no bowers, males may capture females out of the air and forcibly copulate with them. Once this initial function was established, bowers were then co-opted by females for other functions such as use in assessing males based on the quality of bower construction. Recent studies with robot female bowerbirds by Patricelli and collaborators have shown that males react to female signals of discomfort during courtship by reducing the intensity of their potentially threatening courtship. Coleman and colleagues found that young females tend to be more easily threatened by intense male courtship, and these females tend to choose males based on traits not dependent on male courtship intensity.

The high degree of effort directed at mate choice by females and the large skews in mating success directed at males with quality displays suggests that females gain important benefits from mate choice. Since males have no role in parental care and give nothing to females except sperm, it is suggested that females gain genetic benefits from their mate choice, but this has not been established, in part, because of the difficulty of following offspring performance because males take seven years to reach sexual maturity. One hypothesis for the evolutionary causation of the bowerbuilding display is Hamilton and Zuk's "bright bird" hypothesis, which states that sexual ornaments are indicators of general health and heritable disease resistance.[14] Doucet and Montgomerie[15][16] determined that the male bowerbird's plumage reflectance indicates internal parasitic infection, whereas the bower quality is a measure of external parasitic infection. This would suggest that the bowerbird mating display evolved due to parasite mediated sexual selection, though there is some controversy surrounding this conclusion.[17]

This complex mating behaviour, with its highly valued types and colors of decorations, has led some researchers to regard the bowerbirds as among the most behaviorally complex species of bird. It also provides some of the most compelling evidence that the extended phenotype of a species can play a role in sexual selection and indeed act as a powerful mechanism to shape its evolution, as seems to be the case for humans. Inspired by their seemingly extreme courtship rituals, Charles Darwin discussed both bowerbirds and birds-of-paradise in his writings.[18]

In addition, many species of bowerbird are superb vocal mimics. MacGregor's bowerbird, for example, has been observed imitating pigs, waterfalls, and human chatter. Satin bowerbirds commonly mimic other local species as part of their courtship display.

Bowerbirds have also been observed creating optical illusions in their bowers to appeal to mates. They arrange objects in the bower's court area from smallest to largest, creating a forced perspective which holds the attention of the female for longer. Males with objects arranged in a way that have a strong optical illusion are likely to have higher mating success.[19]

Taxonomy and systematics

Two males displaying to a female masked bowerbird, Sericulus aureus, illustrated by John Gould (1804–1881)

Though bowerbirds have traditionally been regarded as closely related to the birds of paradise, recent molecular studies suggest that while both families are part of the great corvid radiation that took place in or near Australia-New Guinea, the bowerbirds are more distant from the birds of paradise than was once thought. Charles Sibley's DNA-DNA hybridization studies placed them close to the lyrebirds;[20] however, anatomical evidence appears to contradict this placement, and the true relationship remains unclear.

Genus Ailuroedus

Genus Scenopooetes

Genus Archboldia

Genus Amblyornis

Genus Prionodura

Genus Sericulus

Genus Ptilonorhynchus

Genus Chlamydera

Note that the gray catbird (Dumetella carolinensis) and black catbird (Melanoptila glabrirostris) from the Americas and the Abyssinian catbird (Parophasma galinieri) from Africa are unrelated birds that belong to different families.

References

  1. 1 2 Frith, Clifford B. (1991). Forshaw, Joseph, ed. Encyclopedia of Animals: Birds. London: Merehurst Press. pp. 228–331. ISBN 1-85391-186-0.
  2. ↑ "Problem Wildlife". Dse.vic.gov.au. 2013-02-27. Retrieved 2013-03-27.
  3. 1 2 "Spotted Bowerbird" (PDF). Retrieved 2013-03-27.
  4. 1 2 Rowland, Peter (2008). Bowerbirds. Australian Natural History Series. Collingwood: CSIRO Publishing. pp. 1–26. ISBN 978-0-643-09420-8.
  5. 1 2 Higgins, P.J. and J.M. Peter (editors); Handbook of Australian, New Zealand and Antarctic Birds, Volume 6: Pardalotes to Shrike-thrushes ISBN 0-19-553762-9
  6. ↑ Frith, Clifford B.; "Egg laying at long intervals in bowerbirds (Ptilonorhynchidae)"
  7. ↑ Based on the formula of egg mass = 0.258m0.73, where m is body mass. From Rahn, H., Sotherland, P. and Paganelli, C. V., 1985. "Interrelationships between egg mass and adult body mass and metabolism among passerine birds" in Journal für Ornithologie 126:263–271.
  8. ↑ Hoyt, Donald F. (1979). "Practical Methods of estimating the Volume and Fresh Weight of Bird Eggs". Auk 96 (1): 73–77.
  9. ↑ Species search by Australian Bird and Bat Banding Scheme
  10. ↑ "Satin Bowerbird". Environment.gov.au. 2007-04-13. Retrieved 2013-03-27.
  11. ↑ Wasser, D. E. and Sherman, P.W.; "Avian longevities and their interpretation under evolutionary theories of senescence" in Journal of Zoology 2 November 2009
  12. ↑ Gilliard, Ernest Thomas (July 1956). "Bower ornamentation versus plumage characters in bower-birds.". Auk 73 (3): 450–451. doi:10.2307/4082011. JSTOR 4082011.
  13. ↑ Kusmierski, Rab; G. Borgia; A. Uy; R.H. Crozier (1997). "Labile evolution of display traits in bowerbirds indicates reduced effects of phylogenetic constraint". Proceedings of the Royal Society of London B 264 (1380): 307–313. doi:10.1098/rspb.1997.0044. PMC 1688255. PMID 9107048. Retrieved 17 November 2013.
  14. ↑ Hamilton, William D; M. Zuk (1982). "Heritable true fitness and bright birds: a role for parasites?". Science 218 (4570): 384–387. doi:10.1126/science.7123238. JSTOR 1688879. PMID 7123238.
  15. ↑ Doucet, Stephanie M.; R. Montgomerie (2003). "Multiple sexual ornaments in satin bowerbirds: ultraviolet plumage and bowers signal different aspects of male quality". Behavioral Ecology 14 (4): 503–509. doi:10.1093/beheco/arg035.
  16. ↑ Doucet, Stephanie M.; R. Montgomerie (2003). "Structural plumage colour and parasites in satin bowerbirds Ptilonorhynchus violaceus: implications for sexual selection". Journal of Avian Biology 34: 237–242. doi:10.1034/j.1600-048x.2003.03113.x.
  17. ↑ Borgia, Gerald; K. Collins (1989). "Female choice for parasite-free male satin bowerbirds and the evolution of bright male plumage". Behavioral Ecology and Sociobiology 25: 445–454. doi:10.1007/bf00300191.
  18. ↑ Diamond, Jared. "Biology of Birds of Paradise and Bowerbirds", Annual Review of Ecology and Systematics, Vol. 17: 17-37 (Volume publication date: November 1986).
  19. ↑ Maxmen, Amy (9 September 2010). "Bowerbirds trick mates with optical illusions". Nature News. doi:10.1038/news.2010.458.
  20. ↑ Sibley, CG; Schodde, R; Ahlquist, JE (1 January 1984). "The relationship of the Australo-Papuan Treecreepers Climacteridae as indicated by DNA-DNA hybridization". Emu 84 (4): 236–241. doi:10.1071/MU9840236.

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