Fig. 1

South Hills crossbills foraging on lodgepole pine cones. Crossbills forage in a very stereotypic manner. a First, crossbills orient so that the vertical axis of the bill is aligned with the elongated surfaces of the cone scales, and then bite between adjacent and often hard, woody scales. Their crossed and decurved mandibles are key because they enable crossbills to exert and withstand strong forces at the mandible tips. Once the mandible tips reach between adjacent cone scales, the lower mandible is abducted laterally (b), spreading the scales apart, and exposing the seeds at their base. After using their tongue to reach into the gap between the scales to lift the seed out, crossbills secure the seed in a lateral groove in their palate. Their lower mandible cracks the seed coat, and the tongue and lower mandible remove and discard the seed coat before the kernel is swallowed (photos: the author)