Escargots for breakfast

The path to the coast winds down a shallow valley where the bedrock lies close to the surface. If you look carefully, each protruding stone is seen to be surrounded by a scatter of broken snail shells, banded yellow, pink or brown.

These dining spots are known as thrushes' anvils: the stones are used by the birds to bash and crack the shells of their favourite snack, so as to get to the juicy flesh inside. You can see the bird in action here. I never see thrushes at it so I suspect the carnage takes place in the early morning when the snails are still abroad in the damp grass. It's learned behaviour: young thrushes have to discover the correct procedure by trial and error. Any hard enough material can be used for an anvil, gravestones are a favourite.

The victims, distinguished by their colourful shells, are banded or grove snails Cepaea nemoralis, and their relationship with their escargot-loving predators demonstrates evolution at work. Studies since the 1950s have found that song thrushes tend to prefer the snails with the most conspicuous shells, and this preference seems to be a major selection pressure for colour polymorphism in the snails. The yellow-banded forms appear to be better camouflaged in grassland, whereas the darker forms are better camouflaged in woodland. It follows then that in this area of short turf it's the reddish snails that are more likely to become a bird's breakfast and therefore the yellowish ones have a better chance of survival and reproduction.

I found this poem by Giles Watson, written with reference to the Iraq war.

Thrush's Anvil

Close by the shamrock and the moschatel,
She keeps her woodland slaughterhouse:
An exposed root, slung with snail flesh
Impaled on sherds of its own shell.
They lie scattered, as if some unsuspected
Cluster bomb had dropped amongst them:
The globules quiver, dripping, gashed open,
Smithereened. No! Do not liken
Her frenzy to our own: her wastage
Is stirred by frantic mother's desperation;
We only wish to thrash profits and democracy
Out of the orphans we create.