♪♪ GIAMATTI: If your neighbor is a woodpecker, you'll know it.
[ Tapping ] ♪♪ Woodpeckers like to make noise.
It's how they claim a territory and show off for mates.
But with heads like hammers and bills like chisels, they do much more than sound off.
Drumming is their song... drilling is how they find food... and highly skilled carpentry is how they craft their remarkable homes.
♪♪ These holes in trees, in many shapes and sizes, make woodpeckers important to everyone in the forest.
[ Birds chirping ] They are architects, engineers, and consummate woodworkers, and this is their "hole" story.
♪♪ ♪♪ [ Birds chirping ] GIAMATTI: Among all the morning voices in a forest, there is one unmistakable sound.
[ Tapping ] It's not made by a voice at all.
[ Tapping continues ] It's a moment of percussion on a wooden instrument.
♪♪ It's the signature sound of a woodpecker.
♪♪ ♪♪ Woodpeckers don't sing.
And they drum in every kind of forest, almost everywhere in the world.
♪♪ ♪♪ They're at home in trees throughout North and South America, across Europe, Asia, and Africa.
the current count is 239 species in all.
♪♪ The Pileated woodpecker is a master of this world of wood and striking in every respect.
He's one of the largest forest birds in North America.
His name comes from the bright red crest across his pileum -- the top of his head from beak to nape.
He drums to announce himself.
Banging your head into a tree has always seemed reckless, but woodpeckers suffer no brain damage.
His head and bill can act like a hammer because his brain is small enough to sustain repeated shocks without injury.
But he does take safety precautions with his eyes.
An extra eyelid closes at the moment of every impact.
[ Distant tapping ] The Pileated slams hard into the decaying wood of a dead tree.
He pounds with intent, then pauses to listen.
♪♪ His favorite quarry is deep in the rotten wood.
He drills again... and listens again.
♪♪ Inside the tree, carpenter ants are frantic.
It's a large colony that has made a home in what must have felt like a very safe place.
♪♪ They moved in when the tree was already dead or dying, its inner layers soft and decaying.
They've chewed extensive galleries with passages and chambers where they are nurturing their young.
Now, a monster is looming.
A 19-inch killer dinosaur is at the door!
He can hear the ants scurrying in panic.
♪♪ The Pileated redoubles his efforts, using his massive beak to rip into the wood.
♪♪ He carves out an enormous oblong opening.
♪♪ Inside, the ants are deploying their best defense.
They've laid down formic acid to deter their predator's attack.
But the woodpecker seems immune... licking the wood as he gets closer and closer to the colony... tasting their chemical deterrent with no ill effect.
♪♪ ♪♪ Inevitably, the determined Pileated prevails.
The ant nest is breached, and the woodpecker begins to feast.
Trees can't hide their secrets from him.
It's as if he can see what's happening inside them.
Perhaps that's no wonder.
Trees have been his world for a very long time.
♪♪ We know that woodpeckers come from an ancient lineage that separated from other birds some 24 million years ago.
And they are different in so many ways.
[ Tapping ] Woodpeckers are all about trees.
Even in the air.
[ Squawking ] Their flight has an undulating pattern.
A few wingbeats are followed by a tucked in glide -- a way of navigating through the branches.
♪♪ They are not long-distance travelers.
They typically fly from tree to tree... and come in for vertical landings.
♪♪ With large, impressively clawed feet, they move across a tree trunk like rock climbers on walls of bark.
♪♪ They can even go exploring upside down.
♪♪ Their short legs are strong and work together with stiff specialized tail feathers to support their weight against the tree.
This tripod provides the leverage they need to work the wood.
♪♪ What began as a way to find food... [ Tapping ] ...developed into a way to communicate.
And so they "talk" to each other by drumming.
Each species taps out its own rhythm, to stake out a territory... and call for a mate.
♪♪ [ Tapping ] ♪♪ When nesting season arrives, they carve deep into trees, hollowing out a family stronghold.
These holes are the woodpeckers' universal trademark.
No matter where they live, every woodpecker of every kind makes a hole for a home.
[ Chirping ] It's a feature that unites the family, and it's what makes them such significant citizens of the forest.
[ Chirping ] In the dark forests of Poland, in Stolowe National Park, wild and eerie calls inhabit the woods.
[ Bird calls ] [ Tapping ] They belong to a pair of rarely filmed Black woodpeckers calling to each other through the trees.
[ Calling ] They are large, imposing birds, jet black with a splash of red on their crowns.
♪♪ [ Woodpecker calls ] These two have made a home in a beech tree and are raising a family 80 feet up in the air.
They dote on their three little chicks only eight days old.
The nest hole is surprisingly deep.
The adults have chiseled down 15 inches into the tree, painstakingly removing all the debris, except for a layer of wood chips that line the bottom of the hole.
At first, the little woodies nap a lot, securely tucked away in their dark wooden womb.
[ Chicks chirping ] But, soon, all the chicks are crying, all of the time... ...not the least interested in concealing their presence.
The nest is so high, it's almost predator proof.
♪♪ Their father, in his full red cap... ♪♪ ...and their mother in her smaller one... ply back and forth with food... while the chicks grow and grow.
♪♪ With daylight approaching 17 hours at the height of June, there's no rest for the weary.
Their forest is not the ancient world Black woodpeckers used to know.
Most of these trees are young, less than a century old.
But they're regaining old ground, and woodpeckers are an important part of their comeback story.
The female is searching for her favorite meal -- carpenter ants.
Her handiwork is easy to find in the forest.
Her old nest holes from previous years, even her winter roosting holes, are bringing other creatures back into this forest.
She's helping Eurasian Red squirrels... Great tits... and Boreal owls find homes here, too, where they can raise their own young.
♪♪ Her life's work is to make her world more diverse, more complex, more like it used to be.
[ Chicks chirping ] Back in the nest, the chicks are beginning to look like real woodpeckers.
From the red feathers sprouting on their own little crowns, it appears they are two females and one male.
♪♪ Their childhoods are brief.
Soon, they will fly from this lofty hole... and three more Black woodpeckers will carry on their important work... making everything new old again.
♪♪ When the year turns and the New England woods are cold and snowy... [ Tapping ] ...the Pileated remains in his forest.
He continues his search for ants and larvae, even when they've gone dormant and are no longer moving.
A dead tree is an almost constant source of insects that he can mine all through the winter.
♪♪ In the very same forest, among the smallest of his cousins are also making their way through the season.
The diminutive Downy woodpecker is named for the soft white feathers that keep them warm.
Their black and white suits, with a dash of red for the male, are a miniature variation of the bold Pileated's, and offer them a way of blending into the trees.
♪♪ Downies search for insects that winter just beneath the bark.
They often join small mixed bands of chickadees... white-breasted nuthatches... and tufted titmice.
♪♪ Several little birds may even roost together overnight if the weather is severe.
♪♪ But as winter thaws and spring arrives, the camaraderie turns to competition.
They all want nests in tree cavities, and a woodpecker hole would do nicely.
The little Downies are highly skilled carpenters and build a new nest every year.
No small bird needing a home can resist a look inside.
A chickadee can excavate its own nest in rotten wood, but a finished Downy nest would be so much easier.
A white-breasted nuthatch wants a simple renovation, something it doesn't have to build from scratch.
A little titmouse can't drill into wood at all.
It needs an empty nest hole that's move-in ready.
[ Chirping ] A lucky house wren has already laid claim to an empty hole and is bringing in her own nesting materials.
♪♪ And a family of tree swallows has commandeered another.
The female has lined the hole with feathers and pine boughs.
♪♪ All these little birds know a woodpecker hole is the safest place in the forest to raise their chicks.
[ Chirping ] As spring reaches north into the woods of Maine, a Ruby-throated hummingbird zings into the scene with a flash of green and red.
He's come all the way from the tropics of Central America, nectaring on flowers as they bloom along his route.
It's early May, and here in the north woods, flowers are still few and far between.
He's pushing the limits of his ability to refuel.
But he's got a brilliant backup plan.
[ Tapping ] He's timed his migration to meet the return of a particular woodpecker -- the Yellow-bellied sapsucker.
Sapsuckers are one of the few woodpeckers to migrate, coming back to the north just as the trees are waking up.
They return to the same trees year after year.
Birches are among their favorites.
They tap into different streams of the tree's plumbing according to the type of sap they seek.
The first holes in early spring intercept the sap coming up from the roots into the wood.
These holes are small, round, and deep.
Immediately, sap wells up in the wounds and spills over.
This is called birch water.
It's thin but full of minerals and hormones.
The tree works to stem the flow and seal the wound.
So the birds tap to the left and tap to the right, moving around the trunk.
As spring unfolds, sapsuckers switch to a living layer of inner bark that sends all the nutrients made by the leaves down to the tree's roots.
♪♪ This sap is loaded with sucrose, and sapsuckers can't resist the sugary syrup.
These shallow holes are large and square and contribute to a conspicuous pattern that moves up the tree.
♪♪ ♪♪ A well-worked sapsucker tree stands out like a beacon to the little Ruby-throated hummingbird.
He plans to claim it as his territory, just in time to impress an arriving female.
She's so eager for birch syrup, she can already taste it.
But... she's going to have to wait her turn.
♪♪ Hummers live so close to the edge, they fiercely defend every source of food they have.
Even when it's an entire tree!
♪♪ ♪♪ Even the little male, who was here first, is given a hard time.
♪♪ Insects, too, love the tree's sweet, sticky flow.
But for them, it's a honey trap.
Ingenious sapsuckers don't need to drill into wood for beetles and grubs.
Sap does the catching for them.
♪♪ And even bees taste better... dipped in sugar.
It may take years, but inevitably, the sapsuckers' holes gird the birch completely.
Nutrients from the leaves can no longer reach the roots, and the tree finally dies.
But death is not the end of a tree's story.
Now it becomes food and shelter for a host of new creatures, chief among them the horned passalus, also known as the patent-leather beetle.
♪♪ This large black beetle finds the perfect home inside dead deciduous trees, with protection from wild swings in the weather... and with all the wood it can eat.
Its larvae will develop here, too, gradually gaining a taste for wood.
The beetles need dead trees to survive... and beetles help keep the forest system humming by nourishing so many birds and mammals.
But the forest has many partners, and the greatest may be these remarkable beings.
♪♪ ♪♪ Fungi bear "fruit" that carry their seed-like spores.
We know them as mushrooms.
♪♪ Neither plants nor animals, fungi recycle all the components of the forest, spreading filaments underground in an organic internet.
♪♪ They break down fallen wood and send its nutrients far and wide... ...to be reincarnated into living trees.
But while they're still standing, dead trees are essential architecture just as they are.
[ Tapping ] ♪♪ Year after year, a small Hairy woodpecker makes nest holes in a flooded stand at the edge of a beaver pond.
♪♪ A dead tree with last year's hole is exactly the home Eastern bluebirds need to raise their own family.
♪♪ ♪♪ As they feed their chicks, the bluebirds have no idea how deeply connected everything in their forest is.
All the bluebirds know is that the nest is precious... and they fiercely defend it... even from the little woodpecker who made it.
♪♪ ♪♪ The value of trees to woodpeckers rises to a dramatic crescendo in central California's Carmel Valley.
It's a story that unfolds across a sweeping savanna of oaks and golden grasses.
These gnarled old oaks have stood their ground for some 500 years.
Their wide-reaching branches are festooned with lace lichen, and their bark is so thick and corrugated, they have weathered almost every challenge for centuries.
But a closer look reveals something astonishing.
♪♪ Acorns, by the tens of thousands, are tattooed into every nook and cranny.
♪♪ Acorns don't grow this way.
Someone has hammered each one into the bark.
[ Squawking ] That someone is actually a band of little round-eyed, clown-faced, Acorn woodpeckers.
♪♪ They live in highly structured families of a dozen or so, each family claiming some 15 acres of oaks and open country.
The trees are their prized possessions.
Because every autumn, they produce a windfall.
♪♪ Thousands upon thousands of nutritious acorns.
♪♪ The acorns are woodpecker gold -- high in vitamins, minerals, fats, and protein.
Collecting them is the woodpeckers' obsession.
♪♪ The acorns are ferried back up to the tree and packed into small holes pecked out for the purpose.
♪♪ This turns the acorns into treasure -- a seasonal abundance that can be made to last.
When other foods are scarce, acorns will be here - safe in their shells and ready to eat.
This is prosperity for the family, a true measure of wealth.
But wealth, it turns out, is a whole lot of work.
♪♪ Now they constantly test and turn the acorns as they dry and shrink, to make sure each one is still snug in its hole.
♪♪ ♪♪ If the hole seems too big... ...they look for a better fit, tapping the acorn back in tight.
It's a process fraught with difficult decisions.
♪♪ And an acorn dropped could be lost forever.
Every member of the family serves on acorn security duty.
♪♪ A ground squirrel boldly climbs the oak only to find the entire tree is woodpecker property.
[ Woodpeckers squawking ] ♪♪ Any outsider, whether furry or feathered, is swiftly dispatched.
What worries the family most are raiding parties of competing Acorn woodpeckers.
All across the valley, groups keep an eye on each other's holdings, waiting for an opening to take them over.
♪♪ Woodpecker spies are everywhere, and though they all look alike to us, the home team always knows who doesn't belong.
[ Squawking ] ♪♪ ♪♪ While Acorn woodies remain tree-bound and devoted to their oaks, other woodpeckers have found success beyond the woods in open country.
[ Squawking ] Across the American West, there lives a remarkable bird who's expanding woodpecker horizons.
She barely looks like a woodpecker at all.
Her feather palette is unlike any other in the family.
Her face is deep red, her belly bright pink.
And she sports an interesting collar of silvery-gray.
This is a Lewis's woodpecker, named for the explorer Meriwether Lewis of Lewis and Clark fame.
Her nest, at least, is traditional woodpecker, a deep hole chiseled out of a large cottonwood.
But from here, she flies out to an open perch to scan the landscape for something to eat.
In nesting season, the grasslands are rich in flowers... and in the insects that come to pollinate them.
As the pollinators rise from their flowers, the Lewis's launches into the air.
Instead of a woodpecker, she becomes a flycatcher, snapping up her prey on the wing.
♪♪ It's a technique called "hawking."
In real time, it's hard to see if she's successful.
But slowed down, it's impressive how adept she is.
♪♪ ♪♪ She returns to the nest trip after trip... ...with beakfuls of nutritious bugs for her chicks.
♪♪ ♪♪ And tops them off with gooseberries for dessert!
♪♪ And then, there are woodpeckers so unorthodox, they've abandoned trees altogether.
Just outside of Tucson, Arizona, in the Sonoran Desert, the Gila woodpecker, with its beautifully patterned back and wings, is tucked into the only tree-like structure around -- a giant saguaro cactus.
Mature saguaros like these could be 200 years old.
The woodpecker holes themselves might date back 50 years.
Many generations of Gila woodies come and go in the life of a grand desert sentinel.
♪♪ Nesting in a cactus takes planning in advance.
After carving out the nest cavity in between the spines, the Gila must wait several months for the inner pulp to dry into a tough, leathery casing.
With the nest ready to go, the male brings an impressive gift to the female, who is now sitting on eggs.
And she delicately consumes it, one spidery leg at a time.
♪♪ Once chicks are in the nest, both parents fly out on foraging sorties... ...with the typical flap-flap-glide that works so well in forests.
♪♪ ♪♪ Though cacti are not trees, and the Sonoran is not a forest, the Gilas have found a woodpecker way to thrive here.
Yet thousands of miles to the south, there's a woodpecker that has left even the semblance of trees far behind.
It lives where no woodpecker should be at all -- in open Alpine meadows 8,000 feet up in the Andes of Argentina.
It carves holes here, not in wood, but in clay cliffs and the banks that line high country streams.
[ Chirping ] This is the Andean flicker.
He's called a "flicker" because his wings are tinged with gold and flash and flicker in the sunlight as he takes to the sky.
♪♪ Out in the grasslands, flickers make a living by using their long woodpecker beaks to probe for worms and insects in the soil.
He's very committed to his mate.
They like to forage close together, hitching across the open terrain like woodpeckers going up a tree.
[ Calling ] They call back and forth to stay in constant contact.
[ Calling continues ] After a moment, the male checks back in.
[ Calling ] This time... there's no reply.
♪♪ ♪♪ He seeks higher ground to call again.
[ Calling ] With no wood to work with, Andean flickers seldom drum.
Calling is all he can do.
[ Calling ] ♪♪ With the anxious moment over, the reunited pair share a brief display... [ Chirping ] ...and settle down to forage again.
♪♪ Adapting to life in the open seems to have made Andean flickers more eager than other woodpeckers for a social life.
♪♪ They even nest in small colonies with maybe a dozen birds sharing a cliff in close proximity.
They also tolerate a small neighbor eager to use their nest holes, too.
Blue-and-white swallows like the same high-altitude grasslands, though they forage in the air and don't compete with the flickers for food.
And their busy chatter adds life to the little village on the cliffs of the flickers' high frontier.
[ Chirping ] ♪♪ The social scene is much more intense back in the oak trees of California.
As nesting season comes around, the family life of Acorn woodies becomes more cooperative, more competitive, and more complex than ever.
In every family group, there may be three or four females that breed... and three or four males that breed, too.
The males are distinguished by white foreheads and bright red crowns.
The females also have white foreheads, but their crowns are black and red.
[ Squawking ] These breeding birds all mate with each other, but never stray outside the group.
The rest of the family are helpers, older siblings waiting to move up to breeding status.
The females manage to sync their breeding to lay their eggs at the same time.
They all use the same nest and take turns incubating the group's eggs.
But it's a male's duty to tend the eggs through the night, and whether this one's a father or not, he's come to take over... and settles down in the dark.
Soon enough, the family is hard at work.
Not every egg hatches, but the family now has three chicks to raise.
The chicks are naked and blind, but they're loud... [ Chicks chirping ] ...and quick to respond when an adult comes with food.
Now the ready supply of acorns really pays off.
The chicks can start out on nutritious acorn mash and never go hungry.
In just 18 days, they're sprouting long, dark feathers.
Soon, they develop their first crown plumage, and they all appear to be male.
All Acorn chicks wear male plumage until their first winter.
No one knows why.
♪♪ At every feeding, each chick wants all the attention.
But they're all getting plenty of food.
Every adult in the group -- the mothers, the fathers, all the helping aunts, brothers, uncles, and sisters -- is bringing them a constant supply.
♪♪ ♪♪ But one female has her own agenda.
Somehow, she's well out of sync with the other females and drops into the nest now to start laying eggs -- right in the middle of the mayhem!
The female tries over and over to incubate the new eggs, but it's no use.
These eggs will never hatch.
But the chicks are doing well under all the relentless parenting.
It's been just three weeks since they hatched.
Now the adults stop entering the nest and encourage the youngsters to climb to the hole.
♪♪ Though this little woodpecker is so eager to look out on an exciting world, he can have no idea what changes are on their way to his valley.
Ready or not, he's launching into it.
♪♪ ♪♪ Every spring, a new class of young woodpeckers graduates from their nest holes to take on the challenge of growing up.
♪♪ Their abilities will surely be tested under the stress of rising temperatures and unpredictable weather.
Some forests will be parched for water.
[ Thunder crashes ] Others will have too much.
♪♪ Already, trees and insects are on the move.
But woodpeckers have skills honed over many millions of years.
They will not be caught standing still.
♪♪ Bright and beautiful Red-bellied woodpeckers have been steadily moving north for some 70 years.
Historically, they were residents of the American Southeast, only rarely seen north of the New York border.
♪♪ But by 1980, Red-bellies were nesting around Boston and the southern Great Lakes.
♪♪ As the millennium dawned 20 years later, they had crossed into Canada, from Quebec to central Ontario.
♪♪ [ Calling ] Today, these woodpeckers-on-the-move are continuing their conquest of the North, a range expansion of a thousand miles.
[ Calling ] ♪♪ A warming world is a boon to them... and they have seized the moment.
♪♪ For every coming change, there will be winners and losers.
And as woodpeckers everywhere face the future, may their resilience and innovative homes help secure their survival.
♪♪ ♪♪ ♪♪ ♪♪ To learn more about what you've seen on this "Nature" program, visit pbs.org.