Choosing What to Eat

Abstract

In the last two chapters, we discussed the way feeding flocks build up on rich food supplies. Birds use the presence of conspecifics or birds of other species to select fields with high surface densities and predictable spatial distributions of earthworms, and areas within fields where worms are locally abundant. Locating rich feeding areas, however, is only one problem facing hungry birds. Earthworms occur at different depths in the soil, in different sizes and so on, making it easier or more difficult for birds to detect and capture them. Is there any way we can predict how (or, indeed, whether) birds should choose between the different types of worm they encounter?