Parental Care by the Willie Wagtail in Southern Victoria

Abstract

The parental care regime of a population of socially monogamous Willie Wagtails was studied over four breeding seasons in southern Victoria. Incubation constancy was 95%, while brooding constancy was 82% early in the nestling period, reducing to 29% later. Nestlings were fed on average 8 times/h early and 12–14 times/h late in their development. Faecal-sac removal occurred 2–3 times/h throughout the nestling period. Territorial intrusions by conspecifics occurred on average less than once/h, and those by potential predators about once/h; most elicited defensive responses from the territory-holders. Male and female partners made equal contributions to most aspects of parental care behaviour; however, females possibly predominated in the care of fledglings, while their male partners initiated new nesting attempts. The magnitude and nature of male parental involvement was consistent with an evolutionary link between biparentalism and social monogamy.