Social organisation and parental care in the Western Yellow Robin Eopsaltria griseogularis in Dryandra Woodland, Western Australia

Abstract

We studied the social organisation and parental care in the Western Yellow Robin Eopsaltria griseogularis in Dryandra Woodland, Western Australia. Of the nine territories in our Tomingley study site, five were of breeding pairs and four were of groups, two of which were cooperative groups of three or four individuals attending nestlings and fledglings. The mean height of six nests, all built in Wandoo Eucalyptus wandoo eucalypts, was 2.7 m above the ground. At one nest, diurnal female incubation constancy was 75.5%, duration of incubation sessions averaged 10.8 minutes and absences from the nest 3.5 minutes. Incubation feeding of the female on the nest by the male occurred at a mean rate of 1.7 times per hour. Mean number of food-delivery trips per hour during the nestling period at a nest with four attendants was 27.3 for Days 6–13, and 16.9 at a nest with three attendants for Days 4–14. Nestling diet was mostly soil arthropods, but also included skinks (Scincidae). Of six nests monitored, young fledged at three (a nest success of 75%), one failed, and the outcome for two nests was unknown. The Eastern Yellow Robin E. australis and the Western Yellow Robin have similar social organisation, incubation behaviour and nestling growth, but rates of food delivery to nestlings were far greater in the Western Yellow Robin. Compared with the Eastern Yellow Robin, nest predation is low in both the Western Yellow Robin, despite a high rate of nest visitation, and White-breasted Robin Quoyornis georgianus. These differences in nest predation and predators between eastern and south-western Australia are discussed.