Episode 5 David Attenborough's Natural Curiosities

The natural world is full of extraordinary animals with

amazing life histories.

Yet certain stories are more intriguing than most.

The mysteries of a butterfly's life cycle,

or the strange biology of the emperor penguin.

Some of these creatures were surrounded by myth

and misunderstandings for a very long time.

And some have only recently revealed their secrets.

These are the animals that stand out from the crowd,

the curiosities I find most fascinating of all.

Some of our most familiar animals puzzled scientific

minds for a surprisingly long time.

The mysterious comings

and goings of barn swallows led to some far-fetched ideas.

While the life cycle of the painted lady butterfly took centuries

to unravel.

But the abilities of some plants

and animals are so remarkable that they seem to be almost supernatural.

In this programme, I investigate the shocking power of a fish that

advanced our understanding of electricity,

and plants with senses that are surprising modern science.

How do these extraordinary powers help the organisms that

produced them?

The freshwater eel is surrounded by legends.

The first Europeans to explore the New World heard amazing

stories about it.

And when, in the 18th century, specimens of this strange fish

reached Europe, they created a sensation.

In 1776, Captain George Baker,

an American mariner and whaler,

made the long and difficult journey from South America across a

raging Atlantic Ocean to bring five live electric eels to London.

These are two of his actual eels.

Captain Baker and his five electric eels, or gymnotas as they were known,

set up shop in the Haymarket and offered two shillings

and sixpence for a shock, or five shillings for a spark.

Baker's eels had come all the way from the lower

reaches of the Amazon and Orinoco rivers,

where he had heard tales from the locals about their astonishing powers.

They called these fish "trembladores".

Humboldt, the famous naturalist and explorer, had described how he

had witnessed horses being killed by the repeated shocks from these fish.

And he himself accidentally stepped on one

and vividly described the effect.

"With each stroke, you feel an internal vibration that lasts

"two or three seconds, followed by a painful numbness.

"All day I felt strong pain in my knees and in all my joints."

I encountered this remarkable fish in its natural environment

when I filmed at the same rivers that Humboldt explored.

There was talk of me swimming with the eel,

but thankfully we had some technical difficulties with the diving

equipment that I was supposed to wear,

and so I stayed safely in a canoe and was able to demonstrate

another subtler, but equally remarkable, side to this fish.

The eels were constantly producing electric discharges.

Somehow they were generating a small, nonstop flowing current.

ELECTRIC DRONE

They were also able to sense electricity and were

attracted to electrical pulses emitted from my underwater detector,

suggesting that electricity plays a key role in their lives.

But at the time of their discovery,

no-one knew the full functions of their extraordinary abilities.

We now know that the shock was caused by electricity,

and I can demonstrate it by touching the animal with an electrode.

Watch.

There. You see?

The scope and the lights are flashing up and down.

Extraordinary.

But this is only a small indication of the real power of this fish.

If I were to try and pick it up, I could get

a jolt of an astonishing 600 volts, which is quite enough to kill me.

This 1960s educational film illustrated the shock,

even though the equipment used prevented

the volunteers from getting its full power.

They were to join hands and then connected to a live eel.

WOMAN SCREAMS

Firm believers in electric eels. Thank you very much.

You can imagine how startling Baker's electric eels

were 200 years ago.

In the 18th century,

electricity was becoming one of the most fashionable areas

of scientific investigation, but it was still very poorly understood.

Very few advances had been made since its discovery 150 years

earlier by Elizabeth I's personal physician, William Gilbert.

Gilbert repeated a trick that had been known about since Greek times.

Rubbing a piece of amber with cat fur, that allowed the amber

to attract a small object like a feather. Let's give it a try.

Here is a bit of amber.

There.

It had always been assumed that this amber effect was caused

by magnetism but Gilbert showed that it was something different.

He named this new force after the Greek word for amber,

electron, and so electricity was born.

Londoners of the time developed a fascination for this magical force.

Showmen staged bizarre spectacles to demonstrate its properties.

In one, a young boy attached to a friction generator

attracted small pieces of paper to his hands.

In another, a gentleman kissed a lady and was repulsed

by the charge carried through her whalebone corset.

No-one knew what to do with electricity

but a better understanding of its nature was slowly emerging.

More and more ingenious ways were developed

to create what we now call static electricity.

And soon it became something more than just a quirk of rubbing amber,

it became visible as a spark.

The ability to produce this characteristic blue spark

along with its invigorating smell became the signature

of this new force and it prompted scientists to make

obvious comparisons with other natural phenomena.

THUNDER

In the American colonies, Benjamin Franklin bravely,

or perhaps foolishly, flew kites into thunderstorms and proved that

lightning and the electric spark were one and the same.

But there's another common property of lightning and static electricity.

That is the ability to shock.

It wasn't long before a comparison was made between the shock from

the early generators and the shock that could be delivered by a fish.

The electric eel wasn't the only kind of fish

known to give humans a powerful jolt.

The ancient Egyptians knew that the electric catfish could also

give shocks and they called it the "Thunderer of the Nile".

And in the nearby Mediterranean lives the torpedo ray.

Its muscle batteries make it so bulky

it can't undulate its body like other rays

but has to propel itself by waving its tail.

Like the electric eel,

it uses its discharge to stun the other fish on which it prays.

Sadly, the pressure of celebrity and having to produce shocks

and sparks to order exhausted Baker's long-suffering eels

and they didn't last the winter.

But two were preserved and expertly dissected by John Hunter,

a very distinguished Scottish surgeon of the time

and he found a great number of striped muscular layers

that proved to be where the electricity was generated.

They are now referred to as Hunter's organs.

He found these muscles along the tail and sides of the eels

arranged in stacks.

One scientist called Galvani believed that animals

had their own natural electricity even without these electric organs

and he tried to prove this by connecting wires to frogs' legs

and making them twitch.

He called this phenomenon animal electricity.

But another scientist called Volta had other ideas.

He proved that the frog was merely a conductor for electricity

with a simple experiment.

Volta replaced Galvani's frog with discs of cloth

soaked in saltwater or acid

and sandwiched them between two different metals.

I can do the same thing with filter paper,

copper two pence pieces and these simple galvanised zinc washers.

Watch.

Tuppenny piece.

Filter.

And washer.

There, nearly 0.6 of a volt.

But the amount of electricity generated was tiny.

Certainly not enough to make the sparks seen from eels.

Unlike Galvani, Volta saw no distinction

between animal electricity and his new electricity from metals

so he now looked at animals to see how he might amplify his new device.

Was it significant that the muscles

producing the electric power in the eels were arranged in stacks?

Volta decided to add more stacks to his electric pile.

We call this way of connecting electric cells together

"in series", and we now know that it increases the voltage.

But Volta was about to find this out for the first time.

He piled up his tiny cells like the bands of muscle

in an electric fish.

Here I've got ten pairs.

And just watch.

Nearly six volts.

Wonderful.

Volta could now produce heat, shocks and even sparks

from electricity in a continuous never-ending stream.

He had made the first battery, partly inspired by the electric eel.

The pieces of the puzzle had come together and the eel's example

had helped to advance our understanding of electricity.

Eels, in fact, contain natural batteries.

Stacks of special muscles.

It's amazing to think when electricity is so much

a part of our lives today that before Volta

the only source of electricity was lightning,

a few static generators

and fish like this incredible electric eel.

Understanding how electric eels managed to find their way around

revealed a hitherto unknown animal sense.

But it's not just animals that have surprised us.

We're now discovering that plants too

have intriguing abilities that are still mysterious.

We think of plants as passive, still and silent.

But they may have more in common with animals than you might think.

New research suggests that they have surprising abilities.

It depends on how you look at them.

I first started seeing plants in a different light

when making a series called The Private Life of Plants.

We used time-lapse photography to reveal the way they move.

The bramble spreads aggressively - seemingly unstoppable.

Other plants pulsed to the rhythms of day and night.

And flower buds explode like fireworks.

So, with speeded up film, we had been able to translate

their time into ours

and to realise that they're constantly on the move.

200 years ago, one plant that moved very quickly indeed

attracted the attention of a great scientific mind.

It appeared to behave like an animal

and could move fast enough to catch its own food.

Charles Darwin was fascinated by the Venus flytrap.

He called it one of the most wonderful plants in the world.

He recognised that it could move in a very different way

to that of plant growth.

This movement was not only fast but also repeatable.

Darwin experimented and found that the traps

are not triggered by raindrops

but only by a very particular stimulation of the leaf hairs,

such as an insect might make.

But what intrigued him most was the speed of the reaction.

He sent one of these flytraps to a friend, Dr Burdon-Sanderson,

who was performing groundbreaking work on muscles and electricity.

His tests confirmed that the tiny electrical discharge

caused by an animal muscle cell contracting was almost identical

to those signals obtained by attaching electrodes to the flytrap

when it was shutting.

Although plants have no muscles,

electrical stimulation enables them to move in a similar way to animals.

Electrical signals cause cells to change the pressure of sap

in their leaves, so creating movement.

As a result, some plants, like animals,

can actively catch their prey.

Recently it's been discovered that other plants use electricity too

but for a very different purpose.

Plants are rooted to the ground and have a small negative charge.

The higher up the plant you go, the greater the electric charge.

This creates an electric field around the flower.

We can't see it but these electrodes are picking up the energy

of this tiny field and converting it into the sound that we can hear.

Bees, on the other hand, have a positive charge.

Friction whilst flying causes them

to lose electrons, leaving them electrically charged.

As a bee approaches a flower, the charge fields around the flower

and the bee interact, and the sound changes...

FALTERING ELECTRONIC BUZZ

..there.

And when it lands, the positive

and negative fields immediately cancel each other out.

As this happens, there are two very surprising consequences.

Firstly, the plant's negatively charged pollen actually

jumps across onto the positively charged bee.

Secondly, the plant has a changed electrical field

and when another bee comes along, it detects this altered

electrical signature and avoids the flower.

The plant is, in effect, telling the bee that it has no nectar

and to come back later.

When the flower has refilled its stores of nectar, it creates

a new electric charge which attracts another passing bee.

This simple on/off signal benefits both the bee and the flower,

but it does have its limitations.

The electrical field is tiny,

so insects can only detect it at close quarters.

But flowers can also draw attention to themselves over much

greater distances and they do this by floating messages in the air.

The perfume of a flower is not just a pleasant smell,

it's also the primary way in which plants communicate with insects.

A rose can contain over 400 chemical compounds and a bee

can recognise a particular combination from over a mile away.

The very latest research has discovered

that 90% of the chemicals made by plants, are also

produced by insects and that is no coincidence.

Most flowers produce scent to persuade insects to visit them,

but others use it in a more sophisticated way...

for protection.

Cabbages communicate with each other using smell.

When the leaves of one plant are being attacked by caterpillars,

it releases a scent which warns its neighbours.

They then produce chemicals in their leaves that caterpillars

don't like and so they avoid being eaten.

And scent also serves to call in the cavalry.

Leaves that are under attack give off a chemical alarm signal that

attracts wasps which obligingly pick off the caterpillar attackers.

So, vegetables, fruits, leaves and flowers are constantly

communicating with each other using touch, vision and smell.

They seem to exploit all the senses, apart, that is, from hearing.

But there are old stories that one particular plant is able to

produce a very strange sound.

Hundreds of years ago, a plant with a root that was thought to

resemble a human body was said to emit a sound that could kill.

The root was known to have strong anaesthetic

and hallucinogenic properties. And in the first century AD,

it was called a mandragora or mandrake as it's now known.

It was associated with magic and the supernatural

and was thought to derive power from a demon that emitted a dreadful

and fatal shriek if the plant was uprooted.

Fortunately, there were creative ways of avoiding

death from the killer sound.

One account advised plugging one's ears

and then tying a starving dog to the mandrake plant.

And then, as the dog lunged for food, the plant would be uprooted.

The dog would tragically die from the mandrake's shriek

but the man would survive.

This particular story may have arisen because drinks made with

the mandrake root can produce hallucinations.

But we're just beginning to realise that the sensory abilities

of a root could be as sophisticated as the rest of the plant.

Latest research suggests that roots are communicating underground.

And we now have the technology to eavesdrop on the roots' world.

Believe it or not, the roots of these corn seedlings can make

and sense sound.

The noise is very quiet but we can hear it with this equipment,

if I place a corn seedling in front of a laser beam Like this.

Now the sound vibration can be detected

and we can hear it through a speaker...

CRACKLING

..there.

That strange crackling is the sound of corn roots growing.

It can be seen as pulses on the screen.

It's been shown, too, that the corn roots respond to the sound

when it's played back to them.

Time-lapse footage shot over just a few hours clearly shows

the roots growing towards the tiny speakers that emit the sound.

There is much speculation

about the purpose of this curious phenomenon.

Perhaps it helps roots avoid growing into hard objects or being too

close to competing plants.

It could act like simple echolocation,

we just don't know but it's the first clear evidence that

plants have a rudimentary form of hearing

and might even be communicating underground using sound.

Sensitive equipment is creating a new window into the plant world

and it seems that, like animals, they have a sophisticated

sense of their environment and possess abilities that not

so long ago, we would have thought of as supernatural.

BIRDSONG

Swallows have successfully nested

and raised their young in this barn for several years.

These chicks will soon leave the nest and make their first

exploratory flights around the farm

but in a few weeks' time they will suddenly vanish.

Where do they go to?

In the past, that gave rise to some extraordinary speculations.

In fact, in the 18th century, it became a very long-running

debate, headed by some well-known Church figures.

And swallows are not the only birds that appear

and disappear with the changing seasons.

For centuries, people speculated about where such birds go.

One explanation was that some birds changed into others by growing

different adult plumage.

Perhaps the redstart turned into a robin...

..or the garden warbler into a blackcap.

Since these species where seldom present at the same time

the explanation seemed entirely plausible.

The barnacle goose was another mystery.

Each winter, huge, noisy flocks of them

appear on European shores, apparently from out of nowhere.

No-one had ever seen them build a nest or raise young.

The barnacle goose gave rise to some extraordinary folklore as this

mediaeval illustration shows.

It was thought that the geese grew on underwater trees,

starting life as small marine creatures called goose barnacles.

Goose barnacles do, of course, exist, they're small

shelled marine organisms with what looks like the head,

which is in fact enclosed by a shell, attached by a stalk, which

was thought to resemble the neck of a bird, to a bit of wood or a rock.

The confusion about the nature of the barnacle goose was put to

good use by some.

Since it was unclear whether it was a bird,

a fish or some other creature, you could surely be

allowed to eat it on days when meat was forbidden by the church.

But the most commonly held belief was that birds

disappear in winter because they hibernated.

Swallows and their close relatives, the swifts and martins,

were thought to do so in mud at the bottom of ponds and rivers

and it's easy to see how this idea originated

because the birds spent much of their time near water, skimming low

over the surface, hunting for insects or taking a drink.

It wasn't until the Middle Ages that another theory was proposed that

some birds may migrate

and one of its strongest proponents was an influential religious leader.

Frederick the second of Hohenstaufen was a powerful holy

Roman Emperor and known for his unorthodox views.

He ignored the philosophy of the Church

and based his knowledge of natural history on direct observation

rather than what was ordained.

Frederick was also a keen falconer and he wrote this book,

The Art Of Falconry,

and in it, surprisingly,

there are entire chapters on the migration of birds.

His confidence came from the fact that,

unlike his contemporaries and those before him,

he had actually observed birds in the field for himself.

He had no doubt about the migration and so,

little patience for the myths surrounding the barnacle goose.

He considered the story to be quite ridiculous

and argued that the birds simply breed in distant lands.

His views started a debate that split people into two camps,

those believing in the old hibernation theory

and those who supported the idea that birds migrate.

This was the start of a new era which was to sweep away myths

and focus instead on facts and careful observation.

Across Europe, the evidence for bird migration started to accumulate.

In Germany, a 12th century monk is said to have taken

a swallow from its nest and attached a parchment note to its leg

that read, "Oh, swallow, where do you live in winter?"

The following spring the bird returned with a note saying,

"In Asia, in the home of Petrus, that is Israel."

The story may not have been true, but it certainly gave the right hint.

In the early 16th century, a Bishop from Sweden called

Olaus Magnus reignited the debate about swallows with this picture.

He claimed that in winter, fishermen often drew up

swallows in their nets, hanging together in a mass.

This astonishing assertion provided ample fuel

for the anti-migration lobby and, unlikely as it was,

the view that swallows spent their winter underwater

became increasingly entrenched.

By the 18th century, the debate about migration versus hibernation

had come to a head and across the continent opinions were divided.

But new evidence was about to come from an unusual source.

Edward Jenner was an English country doctor who also had a deep

interest in natural history.

He noted that although swallows often splash in water

as they skim across it, they never immerse themselves.

Were they to do so, he suggested, their wings would become

so wet that they would be unable to fly.

To test his idea, Jenner reportedly held a swift

underwater for two minutes.

Not surprisingly, it died.

Jenner went on to devise another experiment to

discover where the birds go.

He took 12 swifts from their nests and marked them

by taking off two of their claws.

The following year, some of the birds he'd marked were caught

again in exactly the same spot.

Although Jenner could not discover where his swifts had been

over the winter, he was the first to show that they returned to use

the same breeding sites in the following years.

And we now know that this is true for swallows as well.

About the same time, across the Channel, a German bird enthusiast

had come up with a similar idea.

Johann Frisch caught several birds near his house and attached

to their legs woollen threads like this which he'd dipped

in red watercolour.

He predicted that if swallows really did spend

the winter at the bottom of lakes, the red colour would be washed off.

The following spring, Frisch's swallows returned

and the threads where unchanged.

It was a very simple but very effective experiment.

Evidence against the hibernation theory continued to mount

and eventually a new technique put the final nail in its coffin...

systematic bird ringing.

This bird has just been fitted with its own individual marker.

A small metal ring on its leg with a unique code of numbers.

It's part of a national scheme that's been running for over 100

years and provides scientists with invaluable data on bird movements.

Early in the 20th century, the study of migration really took off.

Birds were recovered on their breeding and wintering grounds

and often en route, too.

600 years after Frederick von Hohenstaufen had first started

the debate, real evidence was beginning to accumulate.

In the summer of 1911, a metal ring just like this one,

was clipped onto the leg of a young swallow in Staffordshire.

The number on the ring was B830.

18 months later, the same bird was caught by a farmer in South Africa.

Here, at last, was the indisputable proof that swallows migrate

and spend the winter thousands of miles away.

Off you go. There we are.

Today, of course, we know that the swallows' migration is

one of the most impressive in all the animal kingdom.

It takes it across the largest desert in the world, the Sahara,

it's a gruelling and dangerous journey

and many die on the way from exhaustion or starvation.

They travel for nearly four months, covering nearly 10,000km

and eventually reach southern Africa.

And bird ringing also helped to dispel the myth of

the barnacle goose.

In the 1960s, a Norwegian expedition, ringed geese nesting

on the Arctic island of Spitsbergen. That autumn, some of the same

birds were sited on the west coast of Scotland, some 2,000km away.

Frederick von Hohenstaufen had been proved to be absolutely correct.

It took centuries to discover the truth behind the swallows'

seasonal movements.

But in their time, they baffled the minds of many great naturalists and

started one of the longest-running of all scientific debates.

But in the end, the true story proved to be even more extraordinary

than the fantastic myths that where invented to explain it.

Just like the swallow,

the painted lady butterfly seems to appear magically out of nowhere

and that started some extraordinary ideas and controversies.

The painted lady is one of our largest butterflies

and a familiar summer visitor to our gardens.

And yet, its appearance

and disappearance each year, has puzzled us for centuries.

It's only now that we're beginning to understand this extraordinary

life cycle and discover where it vanishes each year.

Early naturalists were confused by the sudden

appearance of painted ladies each spring because they were

unaware of the connection between butterflies and caterpillars.

For a very long time it was widely believed that butterflies

arise from rotting material by what was called spontaneous generation.

In the 1830s, a German scientist named Renous was arrested for heresy

for claiming that he could change caterpillars into butterflies.

Arresting someone for something now known to be common knowledge

may seem rather extreme, but at the time, many still believed that

caterpillars and butterflies were completely different creatures,

created by the hand of God.

Needless to say, people had been well aware of the existence of

both butterflies and caterpillars since the earliest times.

But the thought that any two were related,

let alone the same species, seemed impossible...

and it's easy to see why.

Not only do caterpillars and butterflies look like very

different types of animals, but the colours and patterns

of a caterpillar don't match up with those of its adult form.

The only way to know which lava and which butterfly go together

is to keep caterpillars and watch them turn into butterflies.

But it wasn't until the 17th century that anyone left

a record of doing that.

One of the first was a remarkable woman named Maria Sibylla Merian.

Merian was born in Germany at a time

when women still had little formal education

and no role in the scientific world, but she was an accomplished

artist and painted plants and insects she saw around her.

To do that, she kept caterpillars, fed them on leaves

and watched them turn into butterflies.

Merian produced hundreds of beautiful paintings of butterflies

and their stages of development

along with the plants on which they feed.

Her drawings are so exquisite

and detailed that they still rank among the best in the world.

Among the things she observed with great care, were things like this.

A curious, yet strangely beautiful object, it's a chrysalis,

the intermediate stage between a caterpillar and a butterfly.

She was one of the first to record the remarkable change

that takes place in the chrysalis.

It's one of nature's most extraordinary transformations.

At the age of 52, she sailed from Europe to South America on a

two-year expedition to study insects in the tropical jungles of Surinam.

It was an exceptional journey for any naturalist

at the time and particularly for a woman.

When she returned, she produced this beautiful book.

It turned out to be popular

because it was one of the few to be published

not in the scientific language of Latin but in Dutch.

Because of this,

her work was largely dismissed by scientists of the time

but Merian was one of the first naturalists to correctly

connect the caterpillar with its pupa and the adult form.

Today, Merian's book is widely

recognised as a pioneering work of scientific observation

and it put an end to the idea of spontaneous generation.

Around the same time, further evidence for the connection

between butterflies and caterpillars came from a different source.

In 1669, a Dutch scientist by the name of Jan Swammerdam published

the results of experiments which would finally prove that the

caterpillar and butterfly are one and the same animal.

Swammerdam was a master of the miniature and dissected the

caterpillars and pupae of butterflies and moths

under a microscope. With a steady hand and endless patience,

he carefully cut into the layers of skin with tiny scissors

and what he discovered was truly astonishing.

He found some of the body parts of a butterfly.

The structures were fragile and not complete but Swammerdam had proved

that caterpillar and butterfly are, indeed, one and the same animal.

We now know that without the caterpillar, there can be no butterfly.

Yet, for a very long time,

the painted lady seemed to be an exception.

Every spring, the adult butterflies would appear across Britain

without any sightings of their caterpillars.

While some butterflies hibernate in Britain, there was no sign

of painted ladies doing so.

Some speculated that they flew to warmer climates as birds do.

But how could a tiny insect cross the English Channel?

In the 20th century, swarms of butterflies moving across Europe

finally provided evidence that painted ladies do, indeed,

cross the sea.

And they were found to fly all the way from North Africa to Britain.

But there were almost no records of painted ladies making

the reverse trip south.

So, for years, it was thought that Britain must be

a dead-end for the most northerly stragglers.

And then, in 2009, the public was asked to help solve the mystery.

Among 12,000 sightings there were reports of painted ladies

flying out to sea in the autumn.

And a radar station detected them flying south

at heights of 500 metres, way beyond the sight of human eyes.

We now know that the painted ladies migration is a round-trip

of over 12,000km. But it's not made by any one individual.

Each only flies part of the way,

passing on the migratory baton to the next generation.

It's like a relay race with up to six generations of butterflies involved.

The painted ladies epic journey from one continent to the next

would be a truly astonishing feature in any animal

but for a tiny creature like this, it seems really extraordinary.

How does it battle the wind

and the weather and navigate across vast bodies of water?

And with no single individual ever undertaking the whole migration,

how do they find the way?

It seems that painted ladies are pre-programmed to either fly

north or south and this is determined whilst

they are still caterpillars, possibly by temperature

and day length and also by the plants they feed on but how

does this information get passed on from caterpillar to butterfly?

The answer may be hidden within the chrysalis.

Recently CT scanners have allowed us to look inside a pupa.

They reveal that some organs remain intact during the transformation.

A one-day-old pupa clearly shows the gut and breathing tubes

which only change slightly as the chrysalis develops.

Could it be that the brain or nerves also remain intact

and that memories are passed on?

Recent experiments in the lab appear to support this idea.

Scientists taught caterpillars to avoid specific

smells by linking them with an unpleasant reaction.

Later on, as adults, the same individuals remembered these

smells and chose to keep away from them.

If the experiences of a caterpillar can be carried over

to the adult, then maybe cues for migration can also be passed on.

Although we've unravelled much of the painted lady's life-cycle,

many questions remain. How far does each individual travel?

And do offspring follow similar routes to their ancestors?

One day we may know the answers but, for now,

they remain some of the unsolved mysteries of nature.

The arrival each spring of our painted lady butterflies

and our swallows never ceases to delight us

but now we also understand the extraordinary journeys

they undertake when they disappear again at the end of summer.