(Soft piano music over title) (Nature sounds: waves lapping, bird calls) TOM HORTON / NARRATOR: Regular as the moon and the seasons.

(Sound of thunder and rain) NARRATOR: Sudden as the wind and the storm.

Slow as rain percolating through the deep duff of forest floors and wetland ponds.

Up and down.

In and out.

Back and forth.

Here and gone.

Such are the essential rhythms of Chesapeake Bay.

(Bird calls) NARRATOR: Overlaying all of this, connecting the Bay and its watershed to the far reaches of the Western hemispheres is the migration shed: the seasonal comings and goings of creatures from swans, to eels, butterflies to shorebirds.

Their roots worked richly into the Chesapeake fabric.

In late fall, slants of afternoon sun burnish the hues of autumn foliage.

High above a V of tundra swans halloo their arrival.

♪ ♪ They're among the most magnificent birds in North America and the largest of waterfowl.

(Swans calling) NARRATOR: Traveling thousands of miles from the high Arctic summer to their winter home on Chesapeake Bay.

The swans master the buffeting wind as if carving their descent from some firmer, more stable substance than thin air.

♪ ♪ As the birds approach touch down, their aerodynamic lines begin to reshape.

Sinuous... Fluid... Necks arch...

Breasts swell... Big paddle feet swing smoothly down to break their forward motion.

Wings cup, curve, back pedal the air.

A gentle "plish" of water parts to embrace the tired travelers.

(Soft pensive music) NARRATOR: In Britain, there's a word for this glorious return.

"Swan fall," it is called because the birds seem to almost drop from the sky once they reach their wintering grounds.

The swans at first do little but rest and sleep, floating with long necks coiled across their backs.

Bills tucked into a wing.

They're among the wariest of waterfowl, and as they root close to the marsh bank for soft clams and the nutritious root systems of underwater vegetation.

(Playful mysterious music) NARRATOR: One of the adults is always on the lookout for the slightest movement of a raccoon, a fox, a human.

(Ethereal music) (Swan calls) NARRATOR: Some hundred thousand tundra swans migrate east from Alaska and the Yukon on the wing up to 9000 miles a year.

Coming and going.

A majority wintered on the Chesapeake until declines of sea grasses and clams shifted greater numbers to coastal North Carolina.

Overall, the population is stable and healthy.

(More swan calling) (Piano music) NARRATOR: From a distance, they look like snow banks or ice floes clumped together.

♪ ♪ (Swan calls) December slips into January and February, when the swans are often joined by thousands of snow geese.

(Geese and Swan calls) (Bird call) NARRATOR: One day in mid-March, the angle of the sun, the growing length of daylight triggers something deep in the swan's ancestral memories.

It's time to be leaving.

(Swan calls) NARRATOR: Then, it is quiet.

The Bay has lost its wildest voice until swan fall comes around again.

(Sound of creek) NARRATOR: The brackish tidal creek draining fresh water from a remnant crease of swamp transecting suburban sprawl is in full spring mode.

Willows and maples mint new green, ospreys hover, cormorants dive.

The stream of motorists on Racetrack Road takes scant notice.

Maybe the sight of Alexis Park and Keith Whiteford going over the guardrail and down the steep creek bank in hip waders, draws a glance, but none of the drivers could imagine what summons the two Maryland Department of Natural Resources biologists here each spring.

KEITH WHITEFORD: Oh, yeah.

That's not bad.

ALEXIS PARK: Yeah, that's a good catch.

We have an eel trap located at Turville Creek that basically collects glass eels.

As glass eels are entering the coastal bays, from the continental shelf, from the Atlantic Ocean, they're making that journey up looking for freshwater.

So, we have an eel trap out there that we put freshwater through to attract the glass eels.

And as they enter the trap, they will go up the ramp into a well and then drop into a bag that we have attached to the side of the trap.

And we will do counts on those glass eels.

If there's a small number of eels, we'll actually count them individually.

If there's a large number of eels, we do a volumetric count.

KEITH: You want the sample pretty clean.

ALEXIS: Yeah, just checking the sample, making sure there's nothing in there.

It's to give us a relative abundance index of that of the glass eels, of the young of the year.

(Dramatic music) NARRATOR: Along with great blue herons and humans, eels are probably the most widely distributed of all Chesapeake species.

The returning eels will spread throughout the Chesapeake, and it's 40 some rivers and thousands of streams eating, being eaten, vital parts of the ecosystem.

KEITH: In most years our sampling period is approximately 8 to 9 weeks.

Our best year we've caught approximately 250,000 eels.

Our worst year in total was probably 20,000 eels.

And this year, so far we're probably between 70 and 75,000 eels.

And we still have the rest of April.

So, we still have, you know, three more weeks of the survey left.

NARRATOR: The biologists will release the little eels trapped here today to continue their upstream journey.

(Sound of water rushing through dam) KEITH: Before the Conowingo Dam and the other dams were built above Conowingo, the eels were freely able to move up the entire, Susquehanna River up into New York.

And once those dams were built, there was a major blockage, which negatively impacted, you know, a lot of their habitat, being able to reach, you know, all that freshwater habitat.

So there has been a movement to pass eels, either through eel ladders or trap and transport, where they actually catch eels and then move them, and stock them above Conowingo Dam.

So that has been going on since, I think around 2005 or 2006, and they've stocked over, you know, several million eels so far in those last 20 years.

ALEXIS: Glass eels are obviously a delicacy for almost anything and everyone.

As an eel gets larger, they actually become one of the...kind of the top predators in a system.

There's still a lot of unknown about the American eel.

It has a very complex kind of life cycle.

A lot of fish in the Chesapeake Bay are anadromous, where the American eel is catadromous and it actually will spawn out in the ocean in the Sargasso Sea.

The larvae will then drift with the currents and move along the continental shelf, basically turning into glass eels at that time and working their way up into the coastal bays of Maryland and into the Turville Creek area, where we can sample them.

KEITH: They will transform from that glass eel to an Elver stage.

ALEXIS: That's a nice dark one right there... KEITH: And the Elver stage is basically just a small yellow eel...

It will spend up to 15 years in freshwater in the the...the yellow eel stage.

ALEXIS: They all look like they're getting a little darker.

KEITH: Darker...yeah... And then they will basically transform into their last life stage, is the silver eel.

All in preparation to make that migration back out to the Sargasso Sea to spawn.

And from Maryland, that journey could be a thousand miles to 1500 mile journey back to the Sargasso Sea in which they would spawn and then die.

NARRATOR: Frostburg University biologist Rich Raesly uses an electroshocking device to sample Deer Creek on the upper Chesapeake for mature eels that will soon leave for the Sargasso.

What triggers a given eel to go is poorly understood.

RICH RAESLY: We were using a backpack electrofisher to catch eels in Lower Deer Creek.

Ah, the electrofisher has a small battery that puts a weak electric current into the water.

And since eels and other aquatic organisms have more salts in their fluid, body fluids, and tissues than surrounding water, the current passes through the organism and temporarily immobilizes them.

As soon as we cut the current, the eel swims away.

RICH: Deer Creek, uh drains, an area of Harford County, Maryland.

Um, the watershed that it flows through is largely agricultural, but there has been a lot of housing development that can potentially have adverse effects on the organisms that live there.

MAN: Good job.

KEITH: So, I grew up in Baltimore County and across the street from our house, a very, very small stream.

And I was always in the stream catching crayfish, minnows, eels.

It wasn't until I actually went to college to realize every eel that I caught as a little little boy actually traveled well over a thousand miles to 1500 miles from the Sargasso Sea, back to that stream.

(soft music) ♪ ♪ LISA GARRETT: My love of monarchs started when I was young.

My dad, he brought home a National Geographic that showed that, they had found out where the monarch butterflies had been migrating in Mexico.

I was fascinated to find out that the monarchs that we had been seeing flying around were the same monarchs that would fly from Pennsylvania, where I lived all the way down to Mexico and stay over winter in the mountains.

Takes the journey about three weeks.

It could be longer depending on storms and really bad wind fronts.

And when it's bad storms, they need to go into shrubs or trees and hang and protect themselves.

And there might be 20 to 50 or even 100 of them all together.

When I first learned about the monarchs, they kept saying that the population was decreasing.

Well, we used to farm where the fields would be left with hedgerows along the edges.

But in modern times, we're doing better living through chemistry, where farmers are doing, plant to the edge, and then they spray herbicides to kill off anything else that would be competing with the crops.

And when they do that, there's no more milkweed.

That also applies to their plants, like the goldenrods, and many of the asters, and the other plants that they need to fuel their migration.

Those are also been wiped out.

The monarchs, they show us that for thousands of years, that a little teeny creature starts out as a little egg like this, just a little bit bigger than a dot on your paper, and it grows up to be a butterfly that will fly for 2000 miles, stay over winter in Mexico, up in the mountains, sleep there, mate, then fly back up and start the generations all over again.

It shows such resilience.

Migration to me is an amazing thing.

(Bright optimistic music continues) LISA: The female lays the eggs on the underside, near the tip of the leaf of the common milkweed, swamp milkweed, other milkweeds in the milkweed family, that is their host plant.

Then, the egg takes 3 to 4 days to hatch.

When it hatches, the caterpillar comes out.

It's very tiny.

Then, it will eat the milkweed leaves through the next couple days of its life.

After it gets a certain size, it sheds its skin and gets bigger.

It does that five times until it's a full-grown caterpillar.

And then that is a total of about 9 to 12 days, depending on sunlight and temperature.

And it goes and finds a branch or a stick, or the side of a building, or a water fountain.

Lots of weird places.

And they form their chrysalis, which is a beautiful emerald green with gold spots.

They'll be in the chrysalis, um, in the pupa stage for 9 to 12 days, depending on temperature and weather.

And then when it emerges as an adult, it takes it about 4 to 6 hours to come out, to pump its wings.

♪ ♪ And when their wings harden, then about six hours after they've come out, they're able to fly.

The fourth generation, each year that is born at the end of August, the beginning of September, when they come out as an adult, they have much larger abdomens and slightly larger wings.

Something that we learned about monarchs is that their number one source of information is their sight.

And they can see different colors of the spectrum better than us.

They can see the ultraviolet better than us.

So, milkweed must glow to them.

(Dramatic music) ♪ ♪ LISA: I have a local Mennonite family.

(Laughter) LISA: And one of the daughters has been tagging monarchs because they let milkweed grow all around their farm.

(Girl rides bicycles) (Dog barks) - I'm Anna Cox.

We live here in southern Maryland.

We have approximately a 40-acre farm, um, about 15 acres in mixed produce, flowers that we raise for the local farmers market.

Years ago, we took the children to the, different programs at the local nature center.

And one of the programs they had was with tagging monarchs.

So, we said, "Well, that sounds like a good homeschool project for some science experience.

Hands on."

ANNA: Uh, they're very good at netting them.

You have to make a quick swoop and, twist to keep them in the net.

They'll be fluttering around inside the mesh, but it's...it's such a fine weave that it's not going to damage them.

Even those who aren't tagging are generally spotting and they'll holler "monarch!"

And somebody goes running with the net.

Um, my 11-year-old is a little shorter, so she has a ladder propped up against the garden shed, and she'll run to the top of the ladder and that's her lookout post.

We get the tag from the local nature center.

It's just a very tiny circle with, data numbers on it.

YOUNG GIRL: And then you put the tag on a specific spot right here on its little wing.

Right on the larger spot.

So be right here on this side.

It has its code on it.

ANNA: And then you'll release them and they will fly off.

It does not harm them at all.

The tag is lightweight enough that, um, it doesn't impede their activities at all.

And off they go.

One year we actually ran out of tags after 200.

That was our best year ever.

We have a lot of butterflies because we promote the pollinators in general with plantings.

We also try to really limit any kind of spraying so that we don't damage, the pollinator population.

LISA: To think that you were a living creature that crawled around and ate leaves, and then you go into this chrysalis and you jellify and turn into, like, jello, and then you reform yourself into a monarch butterfly.

I think it blows people's minds.

I think that's why people are excited about metamorphosis for years and years.

ANNA: And we believe that that's a, a strong, um, indication of a creator that...that cannot have just happened by chance.

And then the migration, how something that only weighs a few grams, without any map or GPS or having ever done it before, can migrate to an area that they've never been before.

And then make it back later.

Not that same butterfly, but several generations later will actually come back.

And that is a miracle how that can happen.

(Nature sounds) ♪ ♪ NARRATOR: Spring and fall, the coast from Virginia to Delaware swells with birdlife seeking sanctuary and fuel along migratory routes that span whole hemispheres.

(Optimistic music) (Boat engine) - I'm Alex Wilke and I'm a coastal scientist at the Nature Conservancy's Virginia Coast Reserve, which is based on the Eastern Shore of Virginia, which is um located at the very southern end of the Delmarva Peninsula.

I started working here almost 22 years ago and I was doing my graduate work with American oystercatchers, looking at the impacts of predators, and predation on their nesting success.

I immediately fell in love with this place.

There's no other place like it on the entire Atlantic coast.

And one of the groups that really stands out in terms of the relative importance of this place is shorebirds.

(Ocean waves) ALEX: Whether, you're an oystercatcher looking for a good beach to lay your eggs, and raise your young, or whether you're a whimbrel that maybe just arrived here from Brazil on your way to your breeding grounds in the Arctic.

There's vast mudflats to feed on and marshes to rest in so that you can successfully make the rest of that journey.

If you think about these birds flying along the western Atlantic flyway, they've spent all their fat reserves.

They've spent all their energy.

They need to stop and rest and refuel for a period of weeks.

Places like the Virginia Coast Reserve where you have 80 miles of undeveloped barrier island coastline, that is a sweet spot for them.

Within our migratory bird program here at BCR, we...we really have some amazing opportunities to not only manage and protect shorebirds that are on the ground right here in our backyard and using this system, but we also have a really good opportunity to study these birds and look at where else do they go during the rest of their life cycle.

MARIO BALITBIT: So, this is an eastern willet.

There are two types of willets in the world.

There's a western willet that breeds in the middle of the United States and eastern willets that breeds along the coastal Atlantic and to the Gulf, Gulf of Mexico.

During that breeding season, you know, they're here till about September in our region.

Uh, maybe even a little bit late into October.

And then they migrate over the ocean, over the Atlantic towards Bermuda.

And then they drop straight down to South America.

So, they're long distance migrants.

They're traveling about 4000 miles in one direction.

ALEX: There's amazing technology that's available right now that you can put on these birds to track their movements.

And, there's all different kinds, but one kind that we're using right now is called a GPS Transmitter.

These are very small devices.

They're solar powered devices, so they can continually recharge their batteries.

MARIO: You position these around the legs.

Not the wings.

So, you want them to still have full range of motion.

They're collecting a data point every 10 minutes or so.

They're also collecting altitude, which is the most important part of our of our project, essentially, which is relating their migration to an offshore wind site that's being developed out of Virginia Beach.

What we're trying to gauge is how high these birds are flying, and if they might be impacted by the turbines that are being developed out there.

♪ ♪ ALEX: Spring migration here in coastal Virginia is absolutely phenomenal because you have this huge push of shorebirds that are moving from southern non-breeding grounds up to breeding grounds to the north of us.

And that all happens in a relatively short period of time because these birds are wired to get to their breeding grounds, get to business, do what they need to do and then get back to their non-breeding grounds.

We have one opportunity here in particular called "the whimbrel watch," which is a really incredible time of the year.

So, late afternoon as night falls, we sit out on the marsh and we watch these birds rise up out of the marsh and head uh...to the north, and northwest of us.

Some of those birds will literally not touch the ground until they reach their breeding grounds thousands of miles away.

And so, they can be flying for 3...4 or 5 days nonstop.

So, it's an incredible event.

NARRATOR: A long distance champion among shorebird migrators is the red knot, which makes an incredible annual circuit.

Argentina to the Arctic and back: up to 19,000 miles.

Its numbers have fallen to an estimated 26 to 40,000, from an historic abundance of 90 to 180,000.

Flights of famished knots, along with multitudes of stilts, plovers, ruddy ternstones, and other migrants peak along the Delaware Bay shores, each May to gorge on the eggs of spawning horseshoe crabs.

The horseshoe crabs themselves have been struggling here in the world epicenter of their abundance.

Among the most ancient living creatures, they have been little changed in fossil records, stretching back some 400 million years.

The larger females move up onto the beach as the tide rises.

They dig a hole, deposit their eggs, then pull the males along to fertilize them.

A month later, the eggs will hatch.

It's a shotgun approach to procreation that ensures plenty of eggs will be exposed to nourish shorebirds.

A couple of weeks of incessant pecking at tiny gray green crab eggs strewn on the beaches can more than double a bird's weight.

Watching the crabs come ashore on the full moon is to go back in time.

Long before the dinosaurs, before trees, before grass.

Moon and the lap of sea on sand and the shell on shell grating of Limulus Polyphemus.

It's as elemental a scene as one can enter on today's Earth.

(Pensive piano and violin music) ALEX: In general, sadly, across the globe, shorebird populations are in decline.

I don't think there's any debate about that.

And they're struggling in a lot of cases.

You know, habitat loss and degradation in so many parts of the world, it's so bad that these birds are losing the places that they need to survive.

Climate change and sea level rise, you know, their coastal habitats that they depend on are changing or disappearing or their food sources are being impacted.

There's just so many threats that they're facing.

We still have a long way to go to make sure that these populations are robust and resilient.

NARRATOR: Migratory monarchs have been proposed for the federal endangered species list, while eels and tundra swans remain relatively healthy.

Not long after the last monarch has passed in November, as the silver eels stream from the Chesapeake's mouth for Sargassum deeps, there come the lovely wild hallooing of "swan fall," the descent of the tundras from on high to grace the winter time.

Long distance migration is a giant annual bet.

A gamble that destinations and vital way stations will still be there intact, as there's no turning back.

The stakes are nothing less than survival.

These movements, these rhythms are gifts from afar.

Symbols of renewal and hope.

Obligation to protect our little portions of the glorious, webs of life, ritual, and beauty.

♪ ♪