Abstract

The breeding biology and demography of the southern emu-wren (Stipiturus malachurus) were studied over three breeding seasons (2000–02) in the south-west of Victoria, Australia. The nesting biology of the species was typical of the family Maluridae: clutch size ranged from two to three eggs, the incubation period averaged 19 days, and nestlings fledged, on average, 14.2 days after hatching. In total, 6% of nests successfully hatched and 67% of broods produced fledglings, with a mean of 1.8 young fledged per clutch. Nest failure was mainly due to predation, mostly by snakes. Cooperative breeding was observed for the first time in this species, with male offspring delaying breeding to help raise younger siblings. Juveniles were capable of breeding in their first year and dispersed as far as 1.2 km away. Males provided a high level of investment in offspring and this, together with an absence of extra-pair courtship displays, differentiates the emu-wrens from their highly promiscuous relatives, the fairy-wrens. Mortality of individuals was high and the mean duration of pair bonds was short (5.63 ± 0.62 months, n = 62). Population numbers fell dramatically in September 2001, when almost half the adult population disappeared, which suggests that this population could be vulnerable to local extinction.