-In the grasslands of the American West resides a fierce bird of prey unlike any other.

But in order to find it, you have to look in an unusual place -- underground.

[ Owl chitters ] ♪♪ Burrowing owls.

Pint-sized predators... with lots of personality.

Once abundant throughout the Americas, these unique birds are now under threat, but they have a defender.

Owl biologist David Johnson.

-Owls are so incredible and they need our help.

-He's worked tirelessly for over a decade in the hopes of restoring burrowing owls back to part of their historic range in eastern Oregon.

-Here's a rare, rare chance that has not been done anywhere in the world, but that we can do here.

Ah, it's exciting.

I think that we can win this one for conservation.

♪♪ ♪♪ [ Wind howling ] -In north central Oregon... lie the arid grasslands of the Columbia Plateau.

[ Bird chirping ] It's early spring, and arriving back from a long winter away... is a western burrowing owl.

[ Chittering ] He's returning to near where he was born in the hopes of starting a family of his own.

And the first order of business is finding a burrow.

Most western burrowing owls don't make their own nests, and instead, use the old dens of other animals, like badgers or prairie dogs.

But this is no ordinary burrow.

It's man-made.

And it's located in no ordinary place.

The Umatilla Chemical Weapons Depot.

Built in World War II for storing munitions and materiel, it once housed 12% of the US arsenal of chemical weapons.

Today, its nearly 1,000 storage vaults lie empty, but in their shadow are hundreds of other earthen bunkers, home to western burrowing owls.

[ Owl squawks ] At just 10 inches tall, burrowing owls are one of North America's smallest raptors and the world's only bird of prey that nests underground.

With their long legs and habit of being active both day and night, these aren't your typical owls.

Once abundant throughout the west, their numbers have been in decline due mainly to habitat loss, and they are listed as endangered in countries throughout the Americas.

But they've managed to regain a toehold at the Umatilla Weapons Depot, thanks in no small part to the efforts of one man.

-My name is David H. Johnson.

I'm the director of the Global Owl Project, an organization that consists of about 450 people working in 65 countries on the science and conservation of owls.

♪♪ I've been working with owls formally for 43 years now, and I got started when I was 11 years old.

An owl came and landed on my canvas tent when I was camping, a little pup tent.

And I was sitting inside the tent, and the owl was sitting outside in the moonlight, and the shadow on the tent, and it called for 20 minutes.

[ Owl calls ] And so, owls picked me.

I didn't pick owls.

And so, now, they're a constant companion and friend and I see them everywhere I go.

And they're nocturnal, which, I'm a night person, so that's an easy fit.

Now, we're going to check and see if we got anybody.

-Throughout the course of his career, David has helped conserve over a dozen different species of owls... -Yes, sir.

-...across six continents.

-Once you work directly with a given animal, you start to realize when they connect with you.

Okay, then, it's like, "Alright, I'll do what I can to help you."

And so, I felt it's a personal mission.

Alright.

When I get up in the morning, I ask myself, will the things I do today make a difference in 100 years?

And so, it's a tall order, but it helps you focus.

And so, I think about it in that kind of context.

Alright, so, I can't help everything, but I can help the owls.

And so, that's what I've gotten good at and spent my life working at.

We'll bring him back and let him go back in this burrow.

Yeah.

He's already gone down.

Okay.

Alright.

One of the big projects with the global owl efforts is here on the Umatilla Army Depot.

We got started here with a conversation in 2007 about burrowing owls.

They were concerned that... they knew they were losing these animals, and can we do something about them?

We should.

When we first started, there were three or four pairs of owls on the depot.

There had been many more in the past, but they had declined because there was a lack of burrows... because of the lack of badgers.

They had been killed off many years before that.

-Killed as bycatch in a coyote control program, badgers were eradicated from the depot in the 1980s, sending the burrowing owl population into a steady decline.

-It became a rescue mission.

They tried to put out artificial burrows to start with.

-With data collected from hundreds of natural burrows across North America, David created his first artificial burrows, designed both as the perfect home for owls... and to allow David to safely study and monitor the population.

-When I lift this up, I have direct access into the nest chamber proper.

So, then, I can see how many eggs there are, or what the food is, or what's not happening.

-After installing the first 20 burrows around the depot over a decade ago, David saw the first signs of hope.

-We went from three pairs to nine pairs, and then up from there.

Now, we have a chance to support a population and now we can study it.

We've learned a lot about them in the process.

-With just a handful of natural burrows remaining when David first arrived, the depot is now home to more than 90 different artificial burrow sites.

-Owls pass through the regions, and they're searching for burrows because so much of their life is tied up in burrows, and their life is tied around searching for those.

So, if they come through and we put out artificial burrows, boom, they find them.

-And although David has seen steady gains over the past decade, this unique, yet isolated, population still remains vulnerable.

-Not every year can be a good year.

If there's enough of a population, okay, then, there's resiliency for those bad years.

But if there's a low number in the population, it crashes.

There's just no other way around it.

-As he heads into the final years of his recovery effort, David will be closely monitoring the health of the colony.

And if he can document over 40 breeding pairs this year, he'll know that his efforts have been successful and that the owls of the depot can survive without his constant stewardship.

♪♪ ♪♪ The season begins in early spring... when the forest owls return from their wintering grounds.

-Here, owls on the depot arrive in late March or the first part of April.

-First to arrive are the males... who immediately set about claiming one of the 92 burrow sites installed at the depot.

-The males will start to shuffle around and establish territories.

And if they're returnees, they're going to want to come back to their last place.

-Once they've picked a burrow, they're intensely defensive of it.

[ Owl calls ] Some will even nest in the exact same burrow for their entire lives.

But finding a 6-inch-wide tunnel opening from the sky is no easy task.

-What we're trying to do when we make these sand and dirt splays, these are called splays, we're trying to mimic badgers.

When badgers dig their hole, they'll have a 3-foot area around the entrance where the dirt has been kicked out, and the burrowing owls cue on that.

As they fly around, they see, ah, there's something there.

It's hard for them to see the entrance to the tunnel proper, but if they see that there's been some activity, there's... That's why we clear the vegetation around, so it gives them something to concentrate on, to focus on, because they know what they're looking for, you know?

And they know there's probably going to be a tunnel there.

And that's what they really want.

-In addition to a welcome mat, David has carefully located each burrow away from the military silos, where the owls have the best chance of survival.

-Our objective here is we want owls to prosper, okay?

And so, in so doing, you need to think like a burrowing owl and put yourself at their level.

Okay?

And how do they see the world?

How do they see predators?

How do they see this particular site?

There was a site that I first picked when I was first starting.

It was up on a knob.

We knew it was a nice, commanding view, but every year, the coyotes took all the kids.

I moved it 100 meters, now they don't get any.

It's just, sometimes, just a little difference makes all the difference.

-And in the far corner of the depot... a young male has taken up residence in one of David's burrows at site number 77.

An old piece of sagebrush serves as the perfect lookout for any signs of danger.

-Predation is an ever-present issue.

Burrowing owls are small owls and they're prey for a lot of different things -- northern harriers, marsh hawks, red-tailed hawks, coyotes, ravens.

They spend a lot of their energy and time watching for danger.

-Each year, up to 5% of the owls at the depot are lost to predation.

But predators aren't the only thing he has to worry about, as some neighbors aren't too happy about the new arrival.

[ Bird chirping ] ♪♪ ♪♪ But it will take a lot more for him to give up this prime location.

Finding the right burrow is so important that the owls of the depot have developed a unique migration strategy to ensure they get the best pick.

-When we first started work here, we knew that owls migrated.

No idea where they really went.

We assumed that they all went south.

Now, do they go to Arizona, California, Mexico, where?

Didn't really know.

So, we started with geolocators, little tiny backpacks, and they record the ambient amount of light from the sun.

And if you know sunrise and sunset, then you can back-calculate latitude, longitude.

So, we tracked -- we put tags on owls.

Okay?

I put it on pairs of owls, even.

And the female went to California and the male went to eastern Washington, went north to eastern Washington, thought something was -- What's up with that?

So... So, that was brand new, yeah.

And then, they came back together in the following spring and they nested again and all of that.

And so...wow.

So, it turns out that the strategy behind the migration -- the females go south for the winter to put on weight and have a nice mild, calm winter, and they'll come back in great shape to lay eggs.

And the males go north because then, they can be first back.

And so, if they're first back, they get dibs on the burrow and they get dibs on the best burrow, because then, they can be most successful.

So, we found that they'll risk going north and they can only do it here where it's a little bit mild.

In the other states in the plains, it's too cold, they can't do it.

Well, that's a good strategy if the weather's decent and the winters are relatively mild.

Last February was not mild.

It was deep snow and prolonged cold.

So, they got tagged and fewer males came back.

They pay a price for that strategy.

-David can only hope that enough owls return and mate successfully in order to keep the population healthy.

Not long after the males have claimed a burrow, females begin arriving at the depot... having flown 700 miles to return to their breeding grounds.

-Females will arrive just a few days later, and they're going to arrive in good shape, ready to pick their mates, or same one as last year, if they were successful.

-Central to mate selection is the male owl's territorial call.

[ Owl calling ] ...a vocalization unique to each owl.

He'll use it, not only to attract a mate, but also to ward off potential competition.

-They convey a lot of information about themselves, their age, their physical size, their health.

-Burrowing owls will often choose one mate for life, and even after 6 months apart, a female will recognize her partner's call.

-We hear kind of a monotone "cuckoo," but the owls hear many harmonics involved in the notes of the call itself, and it's a very complex call.

-Once reunited, she will head to the burrow and begin making a nest.

-On the depot here, we have put in two or three burrows per site, so the female can pick which one she wants to nest in, and then the male will have the other one for his cache burrow, and he can store extra food in there.

-At the end of a 10-foot-long tunnel lies the burrow chamber.

Buried 3 feet underground, it's a quiet, temperature-controlled room, perfect for building a nest.

While she decides on the ideal place to dig a nest cup, outside, her partner is busy gathering construction materials.

-The males will go out to collect things, materials, for the female.

From a long ways away, you know?

They'll bring in potato skins, onion skins, coyote scats, pieces of wood, grass... Sometimes, we found old work gloves from the farmers' fields.

They'll bring things a mile and a half.

-Though, not everything is suitable nest material.

-Alright.

Let's see what we got.

That's a corn cob the female brought in that the male brought over.

It's a long ways to corn cobs from here.

She brought it in because it's potential for nesting material, but oh, it's too hard.

It ends up in the reject pile.

Some of it's good.

Some of it's not so good.

♪♪ -Out at burrow 77... It appears our young male has found a mate.

[ Owl squawks ] And since they're starting what could be a lifelong partnership, they want to get to know each other first.

-They will have courtship, and they'll be sitting side-by-side, right by the burrow, kind of hunkered down.

So, they'll just sit beside one another and they'll get more and more cozy, just because they don't want to be seen.

They don't trust anything yet.

Still, predation is a real deal.

-Because burrowing owls aren't the only birds of prey returning to the depot.

Soaring in from nearby farm fields is the northern harrier, one of the top predators of burrowing owls at the depot.

♪♪ Alerted by the male's warning call... the female makes a quick run for cover.

Patient hunters, northern harriers will cruise the depot, waiting to catch an owl off guard outside the safety of its burrow.

♪♪ ♪♪ A close call.

♪♪ But the Harrier doesn't seem ready to move on just yet.

♪♪ ♪♪ A young owl peers from the safety of his burrow.

He can't let a harrier get comfortable on his perch.

[ Owl chittering ] ♪♪ But the Harrier doesn't seem too bothered.

A bolder move may be necessary.

Half the harrier's size, he puffs out his feathers to be as intimidating as possible.

But the Harrier only seems to be more interested.

♪♪ It's a tense stand off.

But the burrowing owl is not backing down.

Until, finally, the harrier decides to look elsewhere for a meal.

♪♪ ♪♪ As one of the largest remaining pieces of native grassland, known as shrubsteppe, in eastern Oregon, the Umatilla Chemical Depot is critical habitat for more than just burrowing owls.

Long-billed curlews, the largest shorebird in North America, migrate north from the coasts of California and Mexico to mate and raise their young.

As well as common nighthawks.

A species currently in steep decline, nighthawks fly all the way from South America in order to utilize the depot's pristine habitat.

Thankfully for these imperiled species, a third of the depot is set to become a permanent wildlife refuge administered by the Confederated Tribes of the Umatilla Indian Reservation.

-This is part of the tribe's Aboriginal territory, an important part of it, and it represents an imperiled habitat, shrubsteppe.

It used to be very common throughout their territory, but in Oregon, on the Columbia Plateau, this is some of the very last contiguous pieces of it.

So, the Army Depot inadvertently protected a very large track of this.

This is some of the last that we have, and it's in pretty darn good shape.

What's unique and valuable about it, not just from the critter's eye view, but just ecologically, functionally, the mix of different natural species that we have.

So, if you get these monocultures of cheatgrass, you don't have that kind of mix of forbs and grasses that's so important for some of the species that are shrubsteppe dependents.

We've got a heavy cryptogamic crust, which is a mix of algaes, and bacteria, and fungus, and mosses.

Creates an armor for the soil.

Some of this cryptogram is hundreds of years old, it takes a very long time for it to establish, and once it's disturbed, it's very, very difficult to get it back.

-It's estimated that 87% of native shrubsteppe habitat has been lost across the Columbia Plateau.

For the many species that depend on this fragile ecosystem, the depot will remain a small source of hope.

-We need to be able to have places like this that we can use as laboratories to test methods on large landscapes, where we can actually roll them back and restore them to their natural function and their natural composition to the greatest extent possible.

-By mid-April, all the burrowing owls have returned to the depot, so David and a team of volunteers head out to count nesting pairs and the amount of eggs each has laid.

It will be the first of many data points he will collect in order to understand the health and stability of the owl colony.

-When the females come back, they're in good shape.

They weigh 220 grams, 230 grams, ready to lay their average number of 8.8 eggs on the depot.

They give it their best.

You can tell that this is a female because of her... her brood patch goes up to her neck and it goes out to her wing pits.

It's a huge skin patch, and it's so that she can incubate all those eggs.

So, she's got to cover them, incubate them, turn them, all kinds of stuff.

Usually, by the end of April, females will have laid eggs, and then, the male will be busy hunting.

-For our young male at burrow 77, it's time for his work to really begin.

-So, their job is to bring food off, drop it at the doorstep, give a little pizza delivery call, and off they go hunting again.

-For the next 6 weeks, he will be the primary provider for the female and their growing family.

And like any raptor, he's perfectly adapted for the job, with large ears located asymmetrically on his head and sharp binocular vision, he pinpoints prey with precision.

And once he locks onto a target... he rarely misses.

He's lethal, both in the air... ...and on the ground... ...where his long legs help him chase down prey with deadly accuracy.

He'll be working around the clock, catching insects and small rodents, to ensure the survival of his new family.

-If it's a good food year, great, everything works well.

If it's a bad food year like this year, then things don't go very well.

Okay?

The male's working as hard as he can.

He's losing weight.

She's losing weight.

She'll get down to 140 grams.

You know, she was 230 when she arrived, and the males were 175, and now they're 130, 125, and they're just giving it their all.

-Without enough prey, fewer chicks may survive and the season could even end in total nest failure.

-And so, it's kind of a tearjerker when you realize just how invested they are in specific sites and how they push for success.

And then, if it doesn't work out, there's real consequences.

-David keeps a constant watch for signs of the population's health, and one of the easiest ways is through owl pellets.

All the undigested parts of a day's meal.

-Look at this.

Come over here.

We got one right here.

So, the owls have been eating a lot of insects already.

There's a darkling... part of darkling beetle here that's black.

Right there.

So, a lot of insects.

And this is a little early in the season for them to be doing that, they should be having some more fur.

There's some fur from small mammals.

That's their main -- there we go.

Bones.

That's their main... what drives their nesting cycle stronger.

But this is a good way to tell the activity, but also how they're doing.

It gives you a barometer about how healthy things are right now in this early season.

[ Birds chirping ] [ Thunder rumbles ] -Luckily for the owls... ...a spring rainstorm rolls over the depot.

♪♪ The spring rains bring a boom in the population of insects and rodents across the region.

And it comes just in time.

It's been a month since the first eggs were laid, and deep in the burrows... [ Owlets chirping ] ...the owl families are growing.

A mother at burrow 77 has seven owlets... ♪♪ ...each weighing no more than an ounce.

Just a few days old, their eyes have yet to open, and they're unable to fully thermoregulate, so they huddle near Mum for warmth.

♪♪ It's a healthy new brood.

♪♪ But seven new owlets... means Dad has no time to rest.

As night falls, he flies high into the air.

And then, hovers, intently watching and listening for any movement on the ground.

Fine, comb-like edges on his feathers disturb the flow of air across his wings, muting the sound of his flight, allowing him to both better listen for and go undetected by potential prey.

Even from 30 feet in the air, he can see the faintest movement on the ground.

Once he locates a target, he dives in with deadly accuracy.

♪♪ [ Owlets chirping ] It's a lot of effort.

But a small rodent will be a full meal for multiple chicks.

With all the burrows across the depot brimming with new life, David is back out documenting the progress.

-You can hear the babies.

They're tiny.

[ Owlets chirping ] So, these guys, this one's about 2 days old.

This one hatched today.

There's four.

We record the hatch date of the oldest chick.

When does the first one hatch?

There's two things that it tells us.

One is that then we know that we want to come back 20 days later.

That's about the right time for banding the kids.

And also, if we know hatch date, then we know aspects about climate change and other information about weather effects.

Are they late this year, are they early this year?

Is there a pattern in the hatch dates through time?

That's how you learn and that's a good metric to use.

-David's not the only one who's noticed all the new activity in the burrow.

♪♪ [ Magpie screeching ] It's also gotten the attention of a black-billed magpie.

Magpies are known to prey on the young of other birds, and this one caught Mum at a rare moment away from her chicks.

They may seem helpless, but the owlets have a defense -- at even the slightest hint of danger, they give their defensive call... [ Owlets hissing ] ...which sounds nearly identical to an angry rattlesnake.

♪♪ ♪♪ Best not to find out which one it is.

[ Magpie calls ] As spring gives way to summer, the depot is bustling with new life.

Curlew chicks are taking their first steps away from the nest.

In a tree near the old barracks, a brood of great horned owls tries to stay cool in the midday heat.

And on a hillside behind burrow 77... a litter of coyotes has just emerged from their den.

♪♪ ♪♪ [ Owlets chirping ] After nearly 2 weeks in the burrow, it's starting to feel a little crowded, and the chicks finally take their first timid steps outside.

♪♪ ♪♪ With the chicks venturing out of the burrow, Mum can finally stretch her wings and do some nearby hunting of her own.

♪♪ ♪♪ After 6 weeks of strenuous effort, Dad will take the help.

♪♪ In just 8 short weeks, the owlets will need to be 18 times their current size, meaning each one needs two to three meals a day in order to stay healthy.

So, Mum and Dad work tirelessly to provide a constant meal service.

It's all in the hopes of giving the owlets the best chance for survival during their first winter migration, just a few months away.

♪♪ [ Bird screeches ] At the height of summer... [ Bird calling ] ...the depot is a symphony of birds... [ Bird chirping ] ...and the burrowing owls are no exception.

[ Owl chitters ] [ Owl screeches ] [ Owlet calls ] [ Owls hooting ] Of their many distinct vocalizations, one of the most important is the male's territorial call.

[ Owl hoots ] And it's been of particular interest to David.

-I want to get the guy's voice, but I don't want him to trash my equipment in the process.

We've been recording the calls of the males.

[ Owl hoots in distance ] [ Owl chitters ] So, the idea there is that, when females pick mates, on the depot, they never pick any of their relatives.

They're always unrelated birds.

It makes good sense why they would want to do that, but the calls are part of that story.

[ Owl hoots ] So, the question I've been asking is... do males pass down their vocalizations to their sons, grandsons, great-grandsons, by lineage?

Okay?

So, other vocalization studies on owls, and there are not very many, but they've said, "Okay, this owl is different than this one."

We can tell the differences, but can we tell the similarities?

And is it passed on?

[ Owl chirps ] Well, we've been banding owls here now 10 years.

We know the lineages.

We actually know the individuals.

And through time, the males and females, and their mates, and their offspring.

And so, here's a rare, rare chance to really be able to look at that sort of lineage, relationships, and to look and see if vocalizations are part of that mate selection process.

So, that actually gets into the evolution of owls, right, into one of the core parts of owls that has not been done anywhere in the world, but that we can do here.

Ah, it's exciting.

Okay, trying for the male voice here, and this is a cache burrow.

-Before he can begin analyzing the data, David still has a few more owls to record and capture, but catching a male burrowing owl, and getting him to call on cue, is easier said than done.

So, using his extensive owl knowledge, David devised a way of doing both at once.

-So, I found that, if I took an MP3 player and a little speaker, and I put that in the burrow, and I played the call of an underweight 2-year-old, single male... a punk, okay?

And I put that in there, and I just wanted to be a pesky intruder.

The resident male hears that, and he's not having it.

[ Owl hooting ] He's got no room for somebody like that in there.

And so, that's his burrow.

So, he'll come in first.

They don't really want to fight because the risk of injury is high.

If you get a talon in your eye or something, it's game over.

So, they'll do everything else but.

They'll lower their voice.

They'll sound tougher.

[ Owls hooting ] They come up, they put their wings out, and they strut back and forth.

"Come out, come out, come out, come out!

Don't make me come in there!"

[ Owl hooting ] After a few minutes of that, if that guy doesn't come out, they go in after him.

I catch them all.

♪♪ [ Owl hooting ] -In total, David records the calls of 149 males that span six generations.

-We'll put all those together.

We'll do the analysis blind.

We'll just listen to the calls.

We'll do the analysis and the timing of calls and harmonics of the calls itself.

And then, we'll do a cluster analysis and we'll see how they group together.

And then, we'll look and say, we know all these birds because they're banded, and we can look at the band numbers and say, are they relatives or are they not?

Yeah?

Okay.

We'll find out.

It's exciting.

-But he won't have results until the end of the season, after analysis by a bird vocalization specialist.

Until then, David can only wonder.

-I think we'll find out that they'll be related.

I do think that, I think the genetics are strong and the patterns are strong.

But as a scientist, I'm not going to want to prejudge.

Let's just see it.

We'll do it the hard way and we'll find out.

Then, we'll know the truth.

♪♪ -Back at burrow 77... the young owlets are growing fast, and starting to help out around the burrow, trying their turn at look-out... and guarding against intruders.

♪♪ But real danger lurks nearby.

A coyote from a nearby den is on the hunt.

Dad senses danger and sounds the alarm.

[ Owl screeches ] But even from his high vantage point, it's hard to keep track of a stalking predator in the tall summer grass.

♪♪ Luckily, it's just a curious pup.

♪♪ But an unwelcome guest nevertheless.

[ Owl screeching ] Despite being small enough to fit in your hands, burrowing owls can really pack a punch.

♪♪ After a quick sniff around, the pup decides not to press its luck.

♪♪ ♪♪ ♪♪ As dusk turns to darkness, the burrowing owls across the depot really come alive.

Despite being active during part of the day, the burrowing owls do most of their hunting at night.

-So, what goes on at night?

Well, they're very active hunters.

They generally will hunt small mammals, and insects, and small snakes.

-The chicks wait patiently in the safety of the burrow, while their parents supply a constant stream of food.

Under the cover of darkness, parents will venture farther from the burrow in search of prey.

-So, we find that they will do some long-distance flights, 2, 3, 4 kilometers, to go hunting, the males.

So, they're going long distances and they're very agile.

They're kind of rockets at night.

-A mature owl can catch up to 50 insects in a single night.

-So, catching moths in flight.

They'll catch pocket gophers.

Others have a specialty to wolf spiders.

There was one nest site that I went to, and outside on the apron -- 33 wolf spiders.

This guy was a killer.

Yeah.

They're tough.

Some of these guys are specialists.

-As the day breaks, the chicks are well-fed and ready to do a little adventuring of their own.

♪♪ During the cool hours of early morning is when they're most active.

It looks playful, but it's also practice for becoming skilled predators.

The owlets bob and twist their heads in order to hone their sharp sense of sight and hearing.

With ears that are positioned asymmetrically, a sound will reach one ear before the other, enabling them to quickly triangulate prey with pinpoint accuracy... ...and then go in for the attack.

♪♪ But it's a skill that definitely takes practice to perfect.

And all that work can be pretty exhausting.

Time for a nap.

At 25 days old, the owlets are nearly fully grown, sometimes even outweighing their parents.

It means that it's time for David to band the chicks and collect his final data for the year.

-We band the youngsters on the left leg because they are known-age birds now.

So, when we recapture a bird some years later, it's got a band on its left leg, I can go back in my database and find out, Is it 2 years old?

3, 4, 5, 6, 7, 8?

I know exactly how old that bird is.

And so, that gives us other insights.

Is your population older birds or is it all young birds?

Understanding the age of the population, the age cohort, really tells you a lot about some of the dynamics that are tugging at it and pressing it, you know?

And so, having known-age birds is really, really helpful.

You have to.

-Each owlet gets dusted with flea powder.

And David takes measurements to understand the productivity and health of all the owls at the depot.

Over the past 16 years, David has banded over 6,000 burrowing owls, including every owl hatched at the depot.

-We have some 8-year-old owls on the depot, some 7-year-olds and 6-year-olds.

Those are the grizzled old-timers, and I think more than 6 is an old bird.

And so, it's a short life, and they really go for it, and they give it their all.

-David and his team will work every day for the next 3 weeks to document and band every owl on the depot.

Once they've finished, he will finally know the true health and stability of the population.

♪♪ ♪♪ By late summer, there's a restless energy at the burrow.

♪♪ After watching their parents come and go for the past month, the owlets seem eager to see the wider world.

♪♪ At 30 days old, their flight feathers are all grown in.

And it's time to see what they can do.

♪♪ Soon, everyone is jumping and flapping... seeing who will be the first to fledge.

♪♪ ♪♪ Then, on a particularly windy day, one owlet gets lift off... and stays airborne for an exhilarating few seconds.

Suddenly, everyone's making short flights around the burrow.

♪♪ ♪♪ And it's not long before they're soaring high.

♪♪ ♪♪ ♪♪ Over the course of just 2 weeks, the owlets will go from completely grounded to skilled aviators... ♪♪ ...if not always sticking the landing.

It's now the beginning of the end for our young family at burrow 77.

-At 45 days, they're skilled fliers, okay?

And then, they'll start hunting on their own.

They will follow the male around as he's hunting because now, they can follow him.

And so, instead of waiting for him to come back, they'll go just follow him around.

-By the end of summer, the burrow site will be empty.

-They are here until about the third week of October, and then, they all migrate.

It's like they pick up on a third Thursday and off they go.

The female will go back to exactly the same burrow that she was at last year.

It's amazing.

It's amazing.

♪♪ ♪♪ -For David, it's been an unexpectedly good year.

By the end of the season, he documents a record 63 breeding pairs that hatched more than 450 owlets.

As for his audio study, more analysis is needed, but preliminary results suggest a possible genetic correlation in the timing of the male territorial call.

[ Owl hooting ] And with his unique data set that spans six generations of owls, David is hopeful that there will be even more discoveries as the analysis continues.

-Every year, I learn more.

All the time, more.

I study them.

It's a passion.

No, there's no doubt about that.

I continue to be just astonished.

The more I learn, the more questions I have, and the more fun it becomes to really learn about these animals.

They are absolutely amazing.

-And with a third of the depot becoming a wildlife refuge, David can be sure that this unique population of burrowing owls will continue to thrive for generations to come.

-That's a common question.

Why do owls matter?

I think of it that, if our world didn't have those animals, we would just simply exist.

We're not living anymore.

There's all kinds of examples about the benefits.

We take such short-sightedness of our own values to recognize that these things have been here well before us, and they have everything to value this planet, just like us.

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