Abstract

In south-east Australia, Corvus coronoides and Corvus mellori are slow to reach sexual maturity and spend their immature period in nomadic flocks. Seasonal fluctuations in the numbers of corvids present in any one district correspond to differences in the availability of food and are due largely to the movements of nomadic flocks. Lambing flocks of sheep provide a local abundance of food, mainly in the form of afterbirths and carrion. Few healthy lambs are killed by corvids but many sick animals are finished off by them, a distinction not appreciated by most farmers. Dystocia, twin births, weakness, and desertion are the main circumstances that predispose lambs to serious attacks. Aviary experiments suggest that on the south-east mainland of Australia C. coronoides and C. tasmanicus are the only species capable of damaging lambs.

A change in sheep management, particularly by providing shelter for lambing flocks, will ensure a greater and more permanent improvement in lambing results than will control of corvids which at best has only a temporary effect.