A red crossbill’s beak looks like an accident. The two halves overshoot each other at the tip and cross, like scissors left half shut. It is the tool. The bird slips the crossed points between the scales of a closed pine cone and bites down, and because the tips can’t meet, closing the bill levers the scale open instead, and the tongue takes the seed. Chicks hatch with ordinary straight beaks; the crossing comes in over their first weeks, about when they will need it. In the early 1990s Craig Benkman trimmed the tips of captive crossbills straight, and the birds could no longer get into closed cones until the points grew back. About half of them cross one way and half the other, and each works a cone from the side it was built for. A pair of pliers that does its job by failing to close.