Breeding and population parameters of robins in a woodland remnant in northern New South Wales, Australia

Abstract

Breeding and population parameters of the Scarlet Robin (Petroica multicolor) and Eastern Yellow Robin (Eopsaltria australis) were studied by colour-banding and nest monitoring at Imbota Nature Reserve, a 270-ha woodland remnant, on the New England Tableland of New South Wales in 2000–02. Yellow Robin density was one pair or group to ~30 ha, or 0.1 bird ha⁻¹, with pairs or groups occupying home-ranges of ~5–6 ha. Scarlet Robin density was one pair to ~25 ha or 0.08 bird ha⁻¹, with pairs occupying home-ranges of ~10 ha. Yellow Robins laid in August—January, mainly August—November, and fledging reached a peak in September—October; Scarlet Robins laid in August—December, with a peak of laying and fledging in September—October. Nesting success was 33% for Yellow Robins (n = 40 nesting attempts), with overall production of 0.6 fledglings per attempt, and 9% for Scarlet Robins (n = 45), with production of 0.1 fledglings per attempt; Mayfield values for nest-survival were 24% and 8% respectively. Predation, frequently by medium-sized or large birds, was the main cause of nest-failure (71% for Yellow Robins, 86% for Scarlet Robins). Fledgling survival to independence was 73% for Yellow Robins and 64% for Scarlet Robins. Annual survival of adult Yellow Robins averaged 71%; that of Scarlet Robins was 58%. The Yellow Robin population in Imbota may be self-sustaining, whereas the Scarlet Robin population may depend on immigration.