PARENTAL CARE BY THE WILLIE WAGTAIL IN SOUTHERN VICTORIA

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 a verage 8 times/h early and 12-14 times/h late in their development. Fa ecal-sac removal occurred 2-3 times/h throughout the nestling period. Territorial intrusions by conspecifics occurred on average less than o nce/h, and those by potential predators about once/h; most elicited de fensive 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, whil e their male partners initiated new nesting attempts. The magnitude -a nd nature of male parental involvement was consistent with an evolutio nary link between biparentalism and social monogamy.