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What you're hearing is war among woodpeckers, a species called acorn woodpeckers.

The birds fight long bloody battles over access to trees where these woodpeckers nest and store their food.

You guessed it, acorns.

They build these giant acorn granaries and these are basically Acon storage structures where they store

thousands of acorns every fall. Sajas Barufe with a Smithsonian National

Museum of Natural History.

In park and in dead parts of trees, they make individual holes in which they store one

acorn at a time and some granaries may have tens of thousands of holes.

When woodpeckers that hold high quality territory die,

others come to claim it for themselves.

That's when the fighting begins.

It's a lot of energy that they put in,

and that sort of tells you how valuable big granaries are for them.

So they put in a lot of effort in the short term for this big long-term prize.

Bervay and his colleagues tracked acorn woodpeckers during these power struggles.

The researchers observed up to 12 groups of birds

sparring for a single territory, typically

with three or four birds per clan.

Individual birds may fight more than 10 hours a day for several days.

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