Superb Fairy-wren Malurus cyaneus
Much of our work on the superb fairy-wren has been based around their interesting mating system in which groups of males cooperate with a single female to rear young, yet most (~75% offspring) are sired by males from outside the group. This is the highest known incidence of cuckoldry. This remarkable mating system is produced by female control of fertilization and consistent preference for certain extra-group male genotypes. We found that males living in pairs gain more paternity in their broods compared with dominant males in multi-male cooperative groups. Helpers provide an alternative source of paternal investment, and allow females to express unrestricted mate choice. High levels of extra-group matings mean helpers in this species are often not related to the young they provision, however interestingly helpers still provide care regardless of the degree of relatedness to the young.
To solicit extra-group fertilisations, male superb fairy-wrens display their brightly coloured nuptial plumage during visits to females in neighbouring territories. This ornamental plumage is lost at the end of the breeding season, and reacquired before the next breeding season. Individuals start visiting females as soon as they return to nuptial plumage, often several months before the start of breeding. After finding that males undergo the prenuptial moult earlier as they age and when they are in superior condition, we proposed that the purpose of male displays may be to advertise their quality, and that females use this variation to assess the relative quality of prospective extra-group mates. In addition to plumage, we found males use flower petals in their courtship display when soliciting extra-pair fertilisations. Interestingly, displays were never followed by an immediate copulation, so the behaviour appears most consistent with self-advertisement by males.
When we examined the natal and breeding dispersal of superb fairy-wren, we found this species exhibits male philopatry and female-biased dispersal. Some young males did disperse, and this was generally prompted by breeding vacancies in nearby territories. All females dispersed in their first year, in two distinct phases – the later phase appearing forced due to aggression from mothers. We found dispersal by established breeders was much less common, but still female-biased.
In a separate study, we used field observations and playback experiments to discover that male song is triggered most frequently by the calls of predators. Acoustic properties of this song suggest that it is a long-range signal. We suggest that a possible explanation for this unusual phenomenon is that the male song has evolved through sexual selection as an honest signal to females of male quality, for the purpose of obtaining extra-pair copulations.
Information about our current projects involving superb fairy-wrens can be found on the Research page.
Much of the work described above was conducted as part of Raoul Mulder’s PhD entitled “Evolutionary ecology of the mating system of superb fairy-wrens”. Raoul is currently Head of the School of BioSciences at the University of Melbourne. More information about Raoul can be found on the People page.
More information about this research can be found in these publications:
Cockburn, A, Sims, RA, Osmond, HL, Green, DJ, Double, MC & Mulder, RA (2008). Can we measure the benefits of help in cooperatively breeding birds? The case of superb fairy-wrens Malurus cyaneus. Journal of Animal Ecology 77: 430-438. Full text
Cockburn, A, Osmond, H, Mulder, RA, Double, MC & Green, DJ (2008). Demography of male reproductive queues in cooperatively breeding superb fairy-wrens Malurus cyaneus. Journal of Animal Ecology 77: 297-304. Full text
Cockburn, A, Osmond, HL, Mulder, RA, Green, DJ & Double, MC (2003). Divorce, dispersal and incest avoidance in the cooperatively breeding superb fairy-wren Malurus cyaneus. Journal of Animal Ecology 72: 189-202. Full text
Mulder, RA (1997). Extra-group courtship displays and other reproductive tactics of superb fairy-wrens. Australian Journal of Zoology 45: 131-143. Full text
Mulder, RA (1995). Natal and breeding dispersal in a co-operative, extra-group-mating bird. Journal of Avian Biology 26: 234-240. Full text
Dunn, PO, Cockburn, A & Mulder, RA (1995). Fairy-wren helpers often care for young to which they are unrelated. Proceedings of the Royal Society of London Series B: Biological Sciences 259: 339-343. Full text
Mulder, RA & Magrath, MJ (1994). Timing of prenuptial molt as a sexually selected indicator of male quality in superb fairy-wrens (Malurus cyaneus). Behavioral Ecology 5: 393-400. Full text
Mulder, RA, Dunn, PO, Cockburn, A, Lazenby-Cohen, KA & Howell, MJ (1994). Helpers liberate female fairy-wrens from constraints on extra-pair mate choice. Proceedings: Biological Sciences 255: 223-229. Full text
Mulder, RA & Cockburn, A (1993). Sperm competition and the reproductive anatomy of male superb fairy-wrens. The Auk 110: 588-593. Full text
Mulder, RA & Langmore, NE (1993). Dominant males punish helpers for temporary defection in superb fairy-wrens. Animal Behaviour 45: 830-833. Full text
Langmore, NE & Mulder, RA (1992). A novel context for bird song: predator calls prompt male singing in the kleptogamous superb fairy‐wren, Malurus cyaneus. Ethology 90: 143-153. Full text
Photo: Catherine Payne