Breeding Biology and Social Behaviour of the Eastern Race of the Splendid Fairy-wren Malurus splendens melanotus

Abstract

Black-backed Fairy-wrens Malurus splendens melanotus, a little known race of the Splendid Fairy-wren, were studied at Brookfield Conservation Park, South Australia for three breeding seasons from 1995 to 1997. Here we present observations of breeding biology with an emphasis on female social behaviour as they pertain to mating strategy. Breeding was concentrated during October–December with 50% of females on active nests in November. Females built nests alone, with nest-building activity concentrated in the mornings and afternoons. Inexperienced (one year old) females took longer (mean = 12.27 days) to complete a nest than experienced (two or more years old) females (mean = 7.42 days). The time to complete a nest did not decrease with successive nests or as the season progressed. Incubation lasted 13-14 days (mean = 13.83 days). Females incubated the eggs throughout the day, with longer bouts in the early mornings and late afternoons. The daily periods of incubation increased from days 1-8 and decreased from days 9-14. Female feeding rates (mean = 2.07 visits/nestling/hour) did not vary with larger group sizes, but groups with secondary males made a greater number of total feeding visits to nestlings. Two intensively studied females used a smaller home range than their social mates and one female exhibited differential use of her home range according to the stage of breeding. Males were more likely to be absent from their territories than females (16.3% v. 8.5% of observations, respectively). Females displayed and acted aggressively to potential predators, neighbouring females and dispersing females. Wing-fluttering displays were seen in various contexts and elicited different responses from group members depending on the breeding stage. We discuss our observations in relation to studies of the nominate race M. s. splendens.