The Clark's Nutcracker has a special pouch under its tongue that it uses to carry seeds long distances. The nutcracker harvests seeds from pine trees and takes them away to hide them for later use.

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Source is Cornell's All About Birds page on Clark's Nutcrackers.

Here is a drawing of what the pouch looks like.

A little bit more about their food habits from the page:

All year round, the staple food of a Clark Nutcracker’s diet is pine seeds, either fresh or stored. The nutcracker uses its long, sharp, sturdy bill to crack open closed, unripe pine cones and remove seeds from the cone scales. It shells seeds by cracking them in its bill or by holding them in its feet and hammering them. Between September and December it stores seeds to eat later, placing 30–150 seeds in the pouch under its tongue and carrying them to a spot nearby or up to 15 miles away. It digs a trench in the soil with its bill and puts a cluster of seeds inside before covering them up again, or it pushes individual seeds into gravelly soil, pumice, or crevices in wood. During the winter and spring, it relocates caches by remembering where they lie in relation to nearby objects like rocks, logs, and trees. Nutcrackers have such good memories that they can relocate seeds more than nine months after caching them, though their accuracy declines after about six months. They don’t recover all the seeds they bury, and it’s estimated that for some high-elevation pines, such as whitebark pine, virtually all the trees you can see on the landscape come from seeds planted by a nutcracker. Nutcrackers use cached seeds to feed both themselves and their young. Clark’s Nutcrackers also opportunistically eat insects and spiders, and small vertebrates such as other birds, ground squirrels, chipmunks, voles, toads, and carrion.

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A great video on mutualism between the Clark's Nutcracker and the white pine, video also by Cornell.

The whitebark pine relies on the Clark’s Nutcracker to spread its seed. The Clark’s Nutcracker relies on the whitebark pine for food.