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These acorn shells are the scraps after a big feast.

The long one is from a coast live oak.

This round one's from a black oak.

And this fuzzy one is from a tanoak.

These are the noisy diners: acorn woodpeckers, cracking open and enjoying some acorns.

And here's their well-stocked pantry.

It's called a granary, and it's where they store their acorn collection, high up in these redwoods, to protect it from jays, squirrels and deer.

Acorn woodpeckers are the only animals that store their acorns in carefully-made holes in trees.

The birds drill a few new ones each year.

It took generations to make the thousands of holes in this granary.

Their holes rarely hurt the trees.

They only bore into the bark, where there's no sap that could rot the acorns.

That's why they also store them in dry, dead trees.

Keeping their pantry stocked takes a lot of work.

So acorn woodpeckers live in family groups: four or five of them in something like a commune.

This adult male is showing junior who's boss.

Everyone works and the acorns belong to all of them.

In spring, acorn woodpeckers have their choice of food: Tasty insects.

Oak flowers full of pollen.

Sap that they suck out of shallow holes like these.

When those delicacies are gone in the winter, they'll have acorns.

They don't have much protein, and they taste bitter, but the birds can stock up on them.

If the coast live oaks didn't make acorns that year, the black oaks might.

That's why acorn woodpeckers live where there's more than one species of oak.

The birds need to keep their acorns snug in their holes so other animals can't pull them out.

So they tap the acorns to check.

If they're loose, they look for a smaller hole.

Maybe this one?

This one is just right.

Whoops!

Once in a while, they lose an acorn.

But that's OK. A dropped acorn could sprout another oak for future generations.