OYSTERCATCHERS can tell which half of their prey鈥檚 hinged shell is thinner.
But if in doubt, they peck at the right-hand half. Stephen Lea of the University
of Exeter found that the birds can detect a 0.037-millimetre difference in the
thickness of the two 鈥渧alves鈥� of a mussel shell.
Although this difference is tiny, attacking the thinner valve saves the birds
13 per cent of the effort needed to open a shell, the researchers told a meeting
of the British Ecological Society in Leeds last month. Some 56 per cent of
mussels have thinner right-hand valves, but the birds hammer the right-hand
valves 72 per cent of the time. 鈥淚f in doubt, they go right,鈥� says Lea.