The crossbills are birds in the finch family Fringillidae. These birds are called crossbills because their beaks cross at their tips. Adult males tend to be red or orange in color, and females green or yellow, but there is much variation.

These are specialist feeders on conifer cones, and the unusual bill shape is an adaptation to assist the extraction of the seeds from the cone. These birds are typically found in higher northern hemisphere latitudes, where their food sources grow. Crossbills breed very early in the year, often in winter months, to take advantage of maximum cone supplies.

Feeding behavior

The different species are each adapted to specializing in feeding on different conifer species, with the bill shape optimized for opening that species of conifer. This is achieved by inserting the bill between the conifer cone scales and twisting the lower part of the bill, enabling the bird to extract the seed at the bottom of the scale with its tongue. The Red Crossbill is so dependent upon conifer seeds it even feeds them to its young.

A crossbill's odd bill shape helps it get into tightly closed cones. A bird's biting muscles are stronger than the muscles used to open the bill, so the Red Crossbill places the tips of its slightly open bill under a cone scale and bites down. The crossed tips of the bill push the scale up, exposing the seed inside.