Biology of the Southern Scrub-robin (Drymodes brunneopygia) at Peron Peninsula, Western Australia

Abstract

The ecology of the Southern Scrub-robin was examined at a 55-ha study site on the eastern side of Peron Peninsula, Western Australia. The scrub-robin was a sedentary, ground-dwelling species occurring in pairs, and sometimes alone. Pairs maintained permanent, all-purpose territories throughout the year, and males regularly defended the boundaries of their territories by song and by chasing intruders. Territory sizes ranged from 2.8 to 7.1 ha, with a mean of 4.0 ha. The female alone was observed building the nest and incubating the one egg, but both adults were seen feeding young. The incubation period was estimated at 16 days and the nestling period at 9–12 days. Scrub-robins primarily gleaned prey from leaf litter and sand. Analysis of scats showed that ants comprised a major component of the diet in both spring and summer. Other dietary items in spring included beetles, lepidopteran larvae, termites, hemipterans, spiders and fruit of Enchylaena tomentosa. In summer there was a higher proportion of termites in scats than in spring. The ant fauna within scrub-robin scats was dominated by a species of Iridomyrmex and a species of Crematogaster, both 2–3 mm in length. The Crematogaster species was selected more frequently than it occurred in litter samples, while the Iridomyrmex species was eaten in a lower proportion than sampled in the litter. The scrub-robin’s use of litter substrates for feeding and nesting, and its clutch size of one and potentially low reproductive rate, suggest that it may be vulnerable to changes in the quantity and quality of the litter layer in the Western Australian wheatbelt.