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When winter descends upon Europe,
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many animals have no choice but to leave.
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The migrations of many creatures
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have been a mystery until now.
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And yet they cross oceans and deserts, brave intense weather
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and travel thousands of kilometers unabated.
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Thanks to recent scientific progress
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we are finally able to follow their journey
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and discover the secrets behind their incredible migrations.
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Gray plumage, a dark colored cap.
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Some 20 grams of feathers fluttering in the bushes,
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always alert.
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It's the blackcap.
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A common European bird
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that is also one of the most intriguing.
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Every autumn,
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millions of these birds cross the continent by night
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in search of more welcoming breeding grounds.
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How do they navigate in the dark?
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How do they find their way to their winter homes?
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Even more mysteriously,
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they seem to be taking new migratory routes.
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Thanks to new technologies,
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We are finally starting to understand
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the secrets of their migration.
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(lively music)
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(serene music)
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In southern Sweden,
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nature begins transforming in early September.
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(birds chirping)
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Autumn approaches and the bushes are teeming
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with small birds searching for sweet berries.
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Sparrows, robins,
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chickadees and also an abundance of blackcap warblers.
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Only the male is really worthy of the name
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as the female actually sports a brownish red cap on her head
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This is Northern European Warbler territory
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and this is where it all begins.
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These are migratory perching birds.
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They spent the summer in Sweden
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actively preparing for their great journey.
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In a few months, Sweden will be nothing but ice.
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In order to survive,
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the blackcaps only have one solution, migrating south.
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(lively music)
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With a wingspan around 23 centimeters
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and weighing an average of only 20 grams,
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blackcaps are surprisingly athletic creatures
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capable of traveling thousands of kilometers every year.
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As autumn approaches, the birds behavior changes.
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Suzanne Akesson,
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who studies animal mobility at Lund University,
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is very familiar with these biological transformations.
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They're the precursors to migration.
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They have an internal time program
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that will help them to time various important events
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in the life cycle for example the migration.
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The mechanism is everywhere in the body.
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Every cell is sort of having their timekeeper.
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(lively music)
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When it's biological clock commands it,
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the blackcaps behavior changes drastically.
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First is a radical switch in diet.
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In the summer they are insectivores,
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so they feed on the insects they can find in the bushes
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and then slowly they will start to forage on these berries
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and other fruit.
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This is elderberries.
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So this is the various types of black camps are feeding on
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at this time of year
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and they will try to find them along the migration routes.
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Sweet?
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It's also some extra, I'm not sure.
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In the weeks preceding migration,
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the blackcap begins overeating.
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An intentional fattening that leads to a 30 % weight gain.
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(lively music)
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These sugar-rich fruits allow the bird to rapidly accumulate
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the body fat it needs for its first migratory flight.
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Another important change takes place.
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The blackcap begins to molt its feathers.
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This is a blackcap and a young bird.
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There are some feathers
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that still have the cover around the base.
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So it's molting actually.
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This is very important to have a top flight apprentice
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when you depart a long migration flights.
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With new feathers in a new diet,
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one essential change remains.
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It's a transformation that ornithologists can only see
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with help from special technology.
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In these cages, we feel the activity from above
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and we can see how they become restless.
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A songbird like the blackcaps
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during the other time of year,
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it's mainly sleeping at nighttime
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but the migration season they will suddenly become awake
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and active at night because they use the night to migrate.
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The blackcap which is active during the day
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for most of the year,
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gradually transforms into a nocturnal creature.
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That's because they migrate at night.
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Flying in the dark allows the blackcap
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to limit hot sun exposure
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while also avoiding its primary predators, birds of prey.
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(light music)
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The juvenile birds migrating for the first time,
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make the journey alone without their parents.
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How can they possibly know as they fly away in the dark
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which direction to go?
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To answer this question,
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scientists have developed this peculiar device.
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As night falls,
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the device is placed in the center of a funnel-shaped cage
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and the birds are exposed to the night sky for several hours
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The birds start fluttering
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in the direction they wish to migrate.
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The traces left by their claws on the paper
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indicate that each bird is innately programmed
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to navigate in a certain direction.
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The blackcap is very interesting
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because they have to rely on their internal genetic program
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that will tell them what direction to go
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and how far to migrate.
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The experiment has also shown
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that new behaviors are emerging.
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We have have preferred migration directions
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more to south and southeast
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but nowadays we also find birds that have other preferences
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like in this case, a more westerly orientation.
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There's some large variation between individuals
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but it's also recent evolution of migration.
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That's very exciting with the blackcaps.
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The direction the blackcap takes
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for its migration differs from one bird to another
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yet each of them instinctively knows which course to set.
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Historically, they used to leave Sweden and head south
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but for the past few years
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more blackcaps are choosing new directions
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some of which seemed unusual.
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Before being released,
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these birds are tagged with a small ring
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displaying a unique number for each individual.
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If this blackcap is recaptured elsewhere in Europe,
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its ring will record the path that it took.
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(lively music)
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The time has finally come for the blackcaps to depart.
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This evening, thousands of them will fly south.
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As they leave Sweden,
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the birds crossed Denmark in a single stretch.
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400 kilometers later after eight long hours of traveling,
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they finally reached Germany.
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This first leg seems to follow an almost perfect trajectory
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but how did they orient themselves so precisely?
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Researchers have proven that blackcaps navigate
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by observing the rotation of the celestial hemisphere.
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The stars trace concentric circles in the sky
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that are precisely centered around the geographic North Pole
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It is this stationary reference
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that allows the blackcaps to orient themselves.
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But they aren't born
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with a fully functioning internal compass.
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Young birds need at least 21 nights of studying the stars
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before being able to correctly orient themselves.
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So what happens if a cloudy night sky
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interferes with their celestial compass?
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One scientist has spent years working on a device
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to help the birds fine-tune their navigation.
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At the University of Oldenburg in Germany,
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Henrik Mouritsen and his team have built an apparatus
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that allows them to alter the magnetic field.
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Well, this is a (mumbles) system
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which can be used to change the direction
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and intensity of the Earth's magnetic field.
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Out here, the magnetic nose is pointing north
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and this is actual north
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and if I put this compass inside the coil system here
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where I have set it to change the north-south component,
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you will see now the red arrow points towards South.
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So you can put these birds a little orientation cages,
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they will jump in the direction which they wanna fly
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and then when you turn the direction of the field,
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they started jumping on different directions.
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So they they directly show you but they have now detected
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that the magnetic field has changed.
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The iron core found at the center of the earth
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generates a magnetic field
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that goes from the South Pole to the North Pole.
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The birds don't learn direction
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based on the orientation of this magnetic field
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but rather on another of its characteristics, its tilt.
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The lines of the Earth's magnetic field
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form an angle in relation to its surface
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which varies according to latitude.
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That angle was 74 degrees at their departure point in Sweden
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but it is only 65 degrees at their arrival point.
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The nine degree difference between the two angles
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tells the birds they are now 350 kilometers further south.
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But which part of the bird's body
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contains this particularly efficient GPS?
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Henrik Mouritsen thinks it's based on a visual perception
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of the magnetic field lines.
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Basically the idea is
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that you have a light-sensitive molecule in the bird's eye,
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this absorbs light
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and due to complicated quantum mechanical phenomenon,
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you can generate a chemical composts.
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And to the birds, it would mean that they would actually see
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the magnetic field.
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This chemical compass
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is apparently generated by proteins
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located on the bird's retina.
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On this model which seems like a torture device,
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imagine each nail as one of these proteins
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and the basketball as the retina.
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This is the half ball shape
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would mean that there would be molecules oriented
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in all possible axial directions.
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Then imagine you look along the magnetic field lines
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and let's say the magnetic field lines are running here,
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then this molecule here would be parallel to the field lines
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and let's say that you would see a light pixels
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around the edge of the eye, you would get dark pixels
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and you can now imagine that
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if you now move your eye like this
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you would maybe do a head scan.
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You would scan your head 90 degrees to this side,
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90 degrees to that side.
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Now that light point will kind of move over the retina,
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and this would tell you where the magnetic field lines are
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so that maybe how they could perceive it.
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This mechanism is the very first
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to highlight a quantum physics phenomenon in animal biology.
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It opens up an entirely new investigative field,
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quantum biology.
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Simultaneously guided by the stars
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and the angle of the Earth's magnetic field,
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the blackcaps begin the next leg of their journey Southwest
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along the shore of the North Sea.
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After a long night of flying,
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the exhausted birds must imperatively rest and recuperate.
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The Sun rises over the Flemish coast,
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slowly revealing a green oasis in the distance.
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The Zwin Nature Park.
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(lively music)
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Last night was quite favorable for migration
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and a great number of blackcap are landing here this morning
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This forest is lush with protective shrubbery
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and an abundance of elderberries
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making it an ideal place for a layover.
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(serene music)
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All is going well until.
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(dramatic music)
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Luckily the birds time in this net won't be very long.
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Didier Vangeluwe and his fellow Zwin Park Rangers
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quickly free them up.
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Every year this scientist
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from the Royal Belgian Institute of Natural Sciences
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tags thousands of blackcaps with identification rings.
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Here's another blackcap.
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It's been mostly blackcaps today
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but this one's already tagged.
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It says Rix Museum, Stockholm
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which is the Swedish Royal Museum.
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So this bird was tagged by our Swedish colleagues a few days
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or possibly even a few years ago.
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Today we'll measure him, determine his age
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and update his fact sheet.
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That document is how little by little, we tracked the bird
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00:16:59,310 --> 00:17:01,440
and try to understand how their migration patterns
271
00:17:01,440 --> 00:17:02,563
evolve over time.
272
00:17:03,460 --> 00:17:06,460
Let's put him in this bag so we can take a look at him later
273
00:17:08,160 --> 00:17:10,870
To raise the number of successful catches,
274
00:17:10,870 --> 00:17:13,610
Didier Vangeluwe uses a sonar trap
275
00:17:13,610 --> 00:17:15,863
to lure the birds into the net.
276
00:17:17,240 --> 00:17:19,640
Sonar emits bird calls and songs.
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00:17:21,280 --> 00:17:22,830
It boosts a natural stimulus
278
00:17:22,830 --> 00:17:25,180
that may be a little surprising to many people.
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00:17:26,849 --> 00:17:28,210
But it pertains to the fact that
280
00:17:28,210 --> 00:17:30,440
the birds usually sing at autumn
281
00:17:30,440 --> 00:17:33,390
even though we are well outside of the reproductive period.
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00:17:35,310 --> 00:17:37,340
We think the songs are a natural mechanism
283
00:17:37,340 --> 00:17:38,600
that helps migrating birds
284
00:17:38,600 --> 00:17:42,090
understand if the area they fly over is appropriate.
285
00:17:42,090 --> 00:17:44,340
It can offer them enough food for a few days.
286
00:17:45,520 --> 00:17:48,280
So we imitate nature in order to increase our odds
287
00:17:48,280 --> 00:17:49,823
of catching more birds.
288
00:17:51,397 --> 00:17:54,040
To avoid subjecting the captured birds
289
00:17:54,040 --> 00:17:57,293
to too much stress, they must be tagged quickly.
290
00:17:59,140 --> 00:18:01,330
The researchers take advantage of the moment
291
00:18:01,330 --> 00:18:03,040
to measure and weigh them.
292
00:18:03,040 --> 00:18:05,303
Male wing length, 76.
293
00:18:06,840 --> 00:18:09,090
Their weight is a precious clue.
294
00:18:12,410 --> 00:18:14,710
This one weighs 17.8 grams
295
00:18:14,710 --> 00:18:17,410
which tells us that it arrived last night.
296
00:18:17,410 --> 00:18:18,330
Such light weight
297
00:18:18,330 --> 00:18:21,300
means this bird used up all of its fat reserves.
298
00:18:21,300 --> 00:18:23,030
Now it will take a break for a few days
299
00:18:23,030 --> 00:18:24,573
to replenish its energy.
300
00:18:25,760 --> 00:18:28,080
It will likely give back up to 22 grams
301
00:18:28,080 --> 00:18:30,680
which means it will gain about five grams here Zwin.
302
00:18:31,600 --> 00:18:32,770
That's why it's so important
303
00:18:32,770 --> 00:18:34,780
to manage the natural areas efficiently
304
00:18:34,780 --> 00:18:36,980
and why it's essential to limit pesticides
305
00:18:36,980 --> 00:18:38,493
and encourage biodiversity.
306
00:18:39,400 --> 00:18:40,570
These birds have to eat
307
00:18:41,830 --> 00:18:43,920
and if they don't have a varied biotope
308
00:18:43,920 --> 00:18:45,733
with fruit bushes like they do here,
309
00:18:46,760 --> 00:18:49,410
they won't be able to replenish their energy reserves
310
00:18:50,500 --> 00:18:53,870
which in turn mean they won't be able to migrate efficiently
311
00:18:53,870 --> 00:18:55,970
or might not even survive their migration.
312
00:18:57,780 --> 00:19:00,810
You have to understand that young blackcaps like this one
313
00:19:00,810 --> 00:19:05,063
typically have an annual mortality rate that's around 70%.
314
00:19:07,030 --> 00:19:09,680
The law of the jungle makes it clear.
315
00:19:09,680 --> 00:19:12,160
If the birds are not in the best shape possible,
316
00:19:12,160 --> 00:19:14,303
they will die, there's no other way.
317
00:19:15,730 --> 00:19:17,130
On the other hand,
318
00:19:17,130 --> 00:19:20,440
the survivors will be those that are fully developed,
319
00:19:20,440 --> 00:19:24,470
know how to feed efficiently, understand the weather
320
00:19:24,470 --> 00:19:27,200
and know when they've reached peak physical fitness
321
00:19:27,200 --> 00:19:28,680
so they can choose the right night
322
00:19:28,680 --> 00:19:31,603
to travel those 200, 250 kilometers.
323
00:19:33,140 --> 00:19:35,560
This is what affects population numbers.
324
00:19:35,560 --> 00:19:37,360
Where is this one from?
325
00:19:38,730 --> 00:19:40,520
No come on,
326
00:19:40,520 --> 00:19:43,513
I'm listening but alas, I don't speak Swedish.
327
00:19:45,010 --> 00:19:46,460
As soon as they are freed,
328
00:19:46,460 --> 00:19:49,343
the blackcaps resumed their elderberry feast.
329
00:19:50,450 --> 00:19:51,720
They only have a few days
330
00:19:51,720 --> 00:19:54,093
to replenish their body fat reserves.
331
00:19:55,630 --> 00:19:57,780
For a human weighing 70 kilos,
332
00:19:57,780 --> 00:20:00,280
that's the equivalent of gaining 21 kilos
333
00:20:00,280 --> 00:20:01,503
in less than a week.
334
00:20:03,580 --> 00:20:06,310
The tagging team is happy with their results,
335
00:20:06,310 --> 00:20:09,163
they've tagged 85 blackcaps today.
336
00:20:11,740 --> 00:20:14,860
Each time a tagged bird is recaptured,
337
00:20:14,860 --> 00:20:19,050
that data is meticulously entered in an open database.
338
00:20:19,050 --> 00:20:21,730
Decade's worth of information is stored here
339
00:20:21,730 --> 00:20:24,070
and it's the foundation of everything we know
340
00:20:24,070 --> 00:20:25,823
about blackcap migration.
341
00:20:28,420 --> 00:20:30,520
This is the recapture data map
342
00:20:30,520 --> 00:20:34,343
which shows every blackcap capture in Belgium since 1927.
343
00:20:38,840 --> 00:20:41,580
Each purple dot corresponds to a place in Belgium
344
00:20:41,580 --> 00:20:42,963
where a blackcap was found.
345
00:20:44,730 --> 00:20:47,100
We see that most blackcaps crossing over Belgium
346
00:20:47,100 --> 00:20:49,683
hibernate around the western Mediterranean basin.
347
00:20:51,470 --> 00:20:52,550
While most of the birds
348
00:20:52,550 --> 00:20:55,610
follow a logical path heading south,
349
00:20:55,610 --> 00:20:57,830
some of them migrate in another direction
350
00:20:57,830 --> 00:21:00,403
that may seem absurd, north.
351
00:21:01,720 --> 00:21:04,690
For example, here's a blackcap
352
00:21:05,740 --> 00:21:09,410
that was ringed in Greenburgh in Belgium on September 9th
353
00:21:10,540 --> 00:21:12,060
and this bird was found in Iceland
354
00:21:12,060 --> 00:21:13,733
on November 8th the same year.
355
00:21:14,630 --> 00:21:18,720
So instead of going south east, it went northeast.
356
00:21:18,720 --> 00:21:20,630
It's likely this bird won't survive
357
00:21:20,630 --> 00:21:22,820
but this is an example of the type of mistake
358
00:21:22,820 --> 00:21:24,900
a migrating bird can make.
359
00:21:24,900 --> 00:21:25,990
It can be fatal
360
00:21:25,990 --> 00:21:28,743
but it also allows them to discover new territories.
361
00:21:30,710 --> 00:21:31,870
The tagged blackcaps
362
00:21:31,870 --> 00:21:35,143
now have all the energy they'll need to resume their trip.
363
00:21:38,070 --> 00:21:39,540
As soon as night falls,
364
00:21:39,540 --> 00:21:42,420
they'll begin their journey to their next destination,
365
00:21:42,420 --> 00:21:43,253
France.
366
00:21:46,760 --> 00:21:49,120
Over a million blackcaps have been tagged
367
00:21:49,120 --> 00:21:53,880
in the past century and thanks to the numerous recaptures,
368
00:21:53,880 --> 00:21:57,902
we know there are two primary groups of migratory blackcaps.
369
00:21:57,902 --> 00:22:00,090
Those born in Western Europe
370
00:22:00,090 --> 00:22:03,933
that migrate west around the Alps and head toward Spain,
371
00:22:05,960 --> 00:22:08,820
those born in Eastern Europe avoid the Alps
372
00:22:08,820 --> 00:22:11,773
and migrate east towards the eastern Mediterranean.
373
00:22:14,110 --> 00:22:16,710
These two population groups are separated
374
00:22:16,710 --> 00:22:18,220
by an invisible barrier
375
00:22:18,220 --> 00:22:21,453
that ornithologist call the migration divide.
376
00:22:25,810 --> 00:22:29,220
Although we've known about migration divides for a long time
377
00:22:29,220 --> 00:22:31,420
it was only in the 1970s
378
00:22:31,420 --> 00:22:34,750
that work by Peter Berthold and Andreas Helbig
379
00:22:34,750 --> 00:22:37,373
gave us of better understanding of the phenomenon.
380
00:22:43,330 --> 00:22:45,310
It is at the Max Planck Institute
381
00:22:45,310 --> 00:22:47,570
in Radolfzell, Southern Germany
382
00:22:47,570 --> 00:22:51,950
that Peter Berthold now 78 years old carries out his studies
383
00:22:51,950 --> 00:22:54,260
after the astonishing discovery he made
384
00:22:54,260 --> 00:22:55,693
thanks to the blackcap.
385
00:22:59,503 --> 00:23:01,530
We went to collect blackcaps
386
00:23:01,530 --> 00:23:03,660
at Lake Neusiedl in Austria.
387
00:23:03,660 --> 00:23:06,190
And then we tested them in emmalin funnels
388
00:23:06,190 --> 00:23:07,660
right here in our lab.
389
00:23:07,660 --> 00:23:09,500
Where did the birds want to go?
390
00:23:09,500 --> 00:23:12,890
Obviously east towards Israel in Eastern Africa
391
00:23:12,890 --> 00:23:15,640
and then we took our own birds from around here
392
00:23:15,640 --> 00:23:17,700
that normally want to fly towards Burgundy
393
00:23:17,700 --> 00:23:20,563
and France and Spain, which is what they did.
394
00:23:21,520 --> 00:23:24,170
The next step was to place the birds in an aviary
395
00:23:24,170 --> 00:23:26,633
as mixed couples and then to observe them.
396
00:23:27,580 --> 00:23:30,200
The mixed couples produced hybrid birds
397
00:23:30,200 --> 00:23:33,343
that wanted to migrate south the perfect in-between.
398
00:23:34,220 --> 00:23:36,030
It was incredible.
399
00:23:36,030 --> 00:23:38,470
That's how we proved that migration orientation
400
00:23:38,470 --> 00:23:41,760
is genetically determined or in other words innate
401
00:23:41,760 --> 00:23:43,723
and inherited from the parents.
402
00:23:47,690 --> 00:23:49,680
When migratory directions combine
403
00:23:49,680 --> 00:23:51,540
from two different parent birds,
404
00:23:51,540 --> 00:23:55,223
it leads their offspring to an entirely new destination.
405
00:23:57,230 --> 00:24:00,160
The experiment proved that the birds migratory routes
406
00:24:00,160 --> 00:24:02,090
are clearly based on genetics
407
00:24:02,090 --> 00:24:04,613
and could also change very quickly.
408
00:24:07,500 --> 00:24:09,683
Yet several questions remain.
409
00:24:11,710 --> 00:24:14,703
Do the hybrids survived their migration heading south?
410
00:24:15,810 --> 00:24:18,320
And what happens to the innumerable blackcaps
411
00:24:18,320 --> 00:24:20,363
that follow new migratory routes?
412
00:24:22,860 --> 00:24:24,150
In the heart of Vienna
413
00:24:24,150 --> 00:24:26,810
on a protected island of the Danube River,
414
00:24:26,810 --> 00:24:29,550
Miriam Liedvogel from the Max Planck Institute
415
00:24:29,550 --> 00:24:31,860
For Evolutionary Biology in Plon
416
00:24:31,860 --> 00:24:34,913
is carrying out a large international study.
417
00:24:36,330 --> 00:24:38,450
Her goal is to precisely understand
418
00:24:38,450 --> 00:24:40,570
the blackcaps migratory routes
419
00:24:40,570 --> 00:24:43,083
by following each of them individually.
420
00:24:50,780 --> 00:24:52,280
We walk around on site
421
00:24:52,280 --> 00:24:54,480
and listen carefully for the blackcaps call.
422
00:24:57,200 --> 00:25:00,460
Once we have a general idea of where they're located,
423
00:25:00,460 --> 00:25:01,910
that's where we hang our net.
424
00:25:10,180 --> 00:25:12,000
We're really in the heart of Vienna
425
00:25:12,000 --> 00:25:13,950
in the very center of the city.
426
00:25:13,950 --> 00:25:16,360
The number of blackcaps found on this island
427
00:25:16,360 --> 00:25:18,783
in the middle of the Danube is incredible.
428
00:25:20,080 --> 00:25:23,570
If you walk along that path, you'll hear them everywhere.
429
00:25:23,570 --> 00:25:25,323
They nest very close to here.
430
00:25:26,320 --> 00:25:28,343
Our experiments take advantage of that.
431
00:25:30,380 --> 00:25:32,530
We've already caught a blackcap in our net.
432
00:25:33,860 --> 00:25:34,860
Let's go pick it up.
433
00:25:43,380 --> 00:25:44,770
There.
434
00:25:44,770 --> 00:25:47,083
Hey you, hello.
435
00:25:50,740 --> 00:25:51,573
A blackcap
436
00:25:51,573 --> 00:25:54,053
only weighs about 20 grams on average.
437
00:25:55,360 --> 00:25:57,450
Scientists must hence used tools
438
00:25:57,450 --> 00:25:59,233
adapted to that body weight.
439
00:26:01,520 --> 00:26:03,250
Miriam Liedvogel and her team
440
00:26:03,250 --> 00:26:07,893
have embraced a new piece of technology, a geo locator.
441
00:26:09,360 --> 00:26:13,030
This ultra lightweight receptor only does one thing,
442
00:26:13,030 --> 00:26:16,033
record the date and intensity of sunlight.
443
00:26:19,988 --> 00:26:22,690
That's the light sensor.
444
00:26:22,690 --> 00:26:24,053
It's outside the feathers.
445
00:26:25,200 --> 00:26:27,610
It records the length of the day
446
00:26:27,610 --> 00:26:29,900
and the maximum height of the sun.
447
00:26:29,900 --> 00:26:32,040
Using those two coordinates,
448
00:26:32,040 --> 00:26:34,653
we can calculate the longitude and latitude.
449
00:26:38,470 --> 00:26:41,870
That information allows us to follow their entire journey.
450
00:26:41,870 --> 00:26:43,610
We know when the bird has left here,
451
00:26:43,610 --> 00:26:46,293
where it makes it stops, where it spends the winter.
452
00:26:47,820 --> 00:26:49,610
The device will tell us all of that
453
00:26:49,610 --> 00:26:52,493
when we recaptured the bird and download its data.
454
00:26:54,620 --> 00:26:56,780
The downside of the Geo locator
455
00:26:56,780 --> 00:26:59,530
is that it doesn't transmit data remotely.
456
00:26:59,530 --> 00:27:02,330
The device will have to be retrieved the following year
457
00:27:02,330 --> 00:27:05,640
when this blackcap comes back to Austria.
458
00:27:05,640 --> 00:27:07,830
Luckily, the males are territorial
459
00:27:07,830 --> 00:27:09,550
so they have a tendency to nest
460
00:27:09,550 --> 00:27:12,630
in the same location year after year.
461
00:27:12,630 --> 00:27:14,110
But before any of that,
462
00:27:14,110 --> 00:27:17,060
they first need to survive their journey.
463
00:27:17,060 --> 00:27:20,070
The mini backpack must be precisely placed
464
00:27:20,070 --> 00:27:23,033
so as to not encumber the bird in any way.
465
00:27:24,180 --> 00:27:25,240
So our main objective
466
00:27:25,240 --> 00:27:26,800
is to attach these backpacks
467
00:27:26,800 --> 00:27:28,260
so that they're comfortable for the birds
468
00:27:28,260 --> 00:27:30,690
so that they have enough space to move around
469
00:27:30,690 --> 00:27:33,330
and they're gonna put some body mass on to migrate
470
00:27:33,330 --> 00:27:35,480
and we want to make sure that there's enough leeway
471
00:27:35,480 --> 00:27:38,630
for them to fly comfortably with these backpacks.
472
00:27:38,630 --> 00:27:40,370
One of the goals of this experiment
473
00:27:40,370 --> 00:27:42,270
is to prove that the hybrid birds
474
00:27:42,270 --> 00:27:45,050
which are born in the heart of the migratory divide
475
00:27:45,050 --> 00:27:49,040
are able to migrate south and return to their birthplace.
476
00:27:49,040 --> 00:27:50,960
This is why Austria was chosen
477
00:27:50,960 --> 00:27:52,733
as the site for the experiment.
478
00:27:54,676 --> 00:27:57,453
Austria is ideal for this research.
479
00:27:59,370 --> 00:28:01,230
This is where most of the geo locators
480
00:28:01,230 --> 00:28:02,693
are placed on the birds.
481
00:28:04,670 --> 00:28:08,838
The first year we installed about 200 geo locators in total,
482
00:28:08,838 --> 00:28:12,983
the following year we must have placed another 150 or so.
483
00:28:16,240 --> 00:28:17,290
In Austria,
484
00:28:17,290 --> 00:28:20,513
two groups of blackcap populations intermingle.
485
00:28:21,820 --> 00:28:26,040
Those who migrated West and of those heading east.
486
00:28:26,040 --> 00:28:28,420
To ensure a well-rounded experiment,
487
00:28:28,420 --> 00:28:33,420
the 350 geo locators were set in distinct geographic areas.
488
00:28:34,090 --> 00:28:35,550
Some were placed in the area
489
00:28:35,550 --> 00:28:38,730
that's home to blackcaps migrating West,
490
00:28:38,730 --> 00:28:42,030
others on easterly migrating blackcaps
491
00:28:42,030 --> 00:28:43,650
and others still were placed
492
00:28:43,650 --> 00:28:45,730
in the heart of the migration divide
493
00:28:45,730 --> 00:28:48,433
where the hybrid blackcaps migrate south.
494
00:28:52,540 --> 00:28:55,633
But the southern migration route is highly dangerous.
495
00:28:57,930 --> 00:29:00,263
The birds are forced to brave the Alps,
496
00:29:01,150 --> 00:29:04,490
cross the Mediterranean Sea at its widest part
497
00:29:04,490 --> 00:29:09,263
and tackle the ultimate obstacle, the Sahara Desert.
498
00:29:11,400 --> 00:29:13,960
Are the hybrid blackcaps capable of surviving
499
00:29:13,960 --> 00:29:15,740
such a trying ordeal?
500
00:29:15,740 --> 00:29:18,230
Most scientists wonder.
501
00:29:18,230 --> 00:29:20,790
But Miriam Liedvogel is the only one
502
00:29:20,790 --> 00:29:23,273
who actually has a way to find out.
503
00:29:26,730 --> 00:29:31,003
This young male is ready and his geo locator is in place.
504
00:29:34,340 --> 00:29:36,520
But before beginning the great journey
505
00:29:36,520 --> 00:29:40,063
males and females gather for one last grooming session.
506
00:29:41,510 --> 00:29:43,840
Their feathers need to be in optimal condition
507
00:29:43,840 --> 00:29:46,093
for the upcoming long-distance flight.
508
00:29:53,600 --> 00:29:56,280
This small pond on the edges of the Danube
509
00:29:56,280 --> 00:30:00,320
serves as a peaceful place where many different bird species
510
00:30:00,320 --> 00:30:03,463
that normally keep their distance gather for a bath.
511
00:30:07,770 --> 00:30:09,340
As the Sun sets
512
00:30:09,340 --> 00:30:12,403
the blackcaps embark on their long night of flying.
513
00:30:14,010 --> 00:30:17,263
They join the immense cohort of nocturnal migrants,
514
00:30:18,260 --> 00:30:21,340
a gathering of hundreds of thousands of other blackcaps
515
00:30:21,340 --> 00:30:24,403
already on their way to their winter destination.
516
00:30:26,770 --> 00:30:29,300
After migrating for a month and a half,
517
00:30:29,300 --> 00:30:32,020
the Scandinavian blackcaps heading west
518
00:30:32,020 --> 00:30:33,423
enter the Rhine Valley.
519
00:30:39,945 --> 00:30:43,170
(light music)
520
00:30:43,170 --> 00:30:46,283
Today's pit stop treat, grapes.
521
00:30:50,120 --> 00:30:52,193
Tomorrow, it will be apples.
522
00:30:53,550 --> 00:30:55,770
These sugar heavy fruits are key
523
00:30:55,770 --> 00:30:58,450
as the blackcaps remarkable metabolism
524
00:30:58,450 --> 00:31:01,803
transforms sugar into fat in record time.
525
00:31:05,120 --> 00:31:09,120
A few days later, the migrating birds come face-to-face
526
00:31:09,120 --> 00:31:11,930
with an immense mountain chain blocking their path,
527
00:31:11,930 --> 00:31:12,763
the Pyrenees.
528
00:31:15,520 --> 00:31:17,820
After flying overnight for nine hours,
529
00:31:17,820 --> 00:31:20,093
they once again need to refuel.
530
00:31:22,540 --> 00:31:25,630
How do the blackcaps keep up such an intense effort
531
00:31:25,630 --> 00:31:26,803
week after week?
532
00:31:28,780 --> 00:31:30,930
In the matter of long-distance runners,
533
00:31:30,930 --> 00:31:33,340
the blackcaps dig deep into their reserves
534
00:31:33,340 --> 00:31:35,233
on each leg of their migration.
535
00:31:40,080 --> 00:31:43,183
But they do so much more efficiently than mankind.
536
00:31:50,270 --> 00:31:52,700
The blackcaps remarkable metabolism
537
00:31:52,700 --> 00:31:56,930
allows it to transform lipids into energy ten times faster
538
00:31:56,930 --> 00:31:58,713
than most other vertebrates.
539
00:32:01,240 --> 00:32:05,400
During its journey it powers its strong pectoral muscles
540
00:32:05,400 --> 00:32:09,123
with a constant flow of energy from its body fat reserves.
541
00:32:10,470 --> 00:32:12,810
This is how the blackcap is able to fly
542
00:32:12,810 --> 00:32:15,113
for hours on end without foraging.
543
00:32:17,780 --> 00:32:18,833
Unlike this runner.
544
00:32:28,740 --> 00:32:30,260
It's late November
545
00:32:30,260 --> 00:32:32,510
and the first winter sleet hits the Pyrenees.
546
00:32:33,630 --> 00:32:35,900
The blackcaps make their way across
547
00:32:35,900 --> 00:32:38,513
either by going around or over the top.
548
00:32:40,910 --> 00:32:44,860
In two weeks, these passerines cover 1200 kilometers
549
00:32:44,860 --> 00:32:46,563
to get to southern Spain.
550
00:32:49,220 --> 00:32:52,310
For most of the blackcaps coming from Western Europe
551
00:32:52,310 --> 00:32:56,321
arriving in Andalusia, marks the end of their journey.
552
00:32:56,321 --> 00:32:58,821
(light music)
553
00:33:03,560 --> 00:33:06,530
Having left Northern Europe more than two months ago,
554
00:33:06,530 --> 00:33:09,483
the birds finally reached their winter destination.
555
00:33:12,390 --> 00:33:16,050
Located on the southernmost tip of the Iberian Peninsula,
556
00:33:16,050 --> 00:33:18,140
the Lowes Alcornocolles massive
557
00:33:18,140 --> 00:33:21,314
is in El Dorado for migrating blackcaps.
558
00:33:21,314 --> 00:33:23,897
(serene music)
559
00:33:26,800 --> 00:33:29,410
The young birds that survived their first journey,
560
00:33:29,410 --> 00:33:31,810
discover their new surroundings.
561
00:33:31,810 --> 00:33:33,950
A world of abundant food
562
00:33:33,950 --> 00:33:35,820
and where the temperature rarely drops
563
00:33:35,820 --> 00:33:37,653
below 10 degrees Celsius.
564
00:33:42,400 --> 00:33:43,770
If blackcaps could speak
565
00:33:43,770 --> 00:33:45,960
the native languages of their homelands,
566
00:33:45,960 --> 00:33:48,883
this forest would sound like the Tower of Babel.
567
00:33:53,170 --> 00:33:56,640
One would hear English, German,
568
00:33:56,640 --> 00:33:59,363
French and Scandinavian languages.
569
00:34:00,470 --> 00:34:04,323
But another language would also be present, Spanish.
570
00:34:07,320 --> 00:34:09,320
That's because these mountains are home
571
00:34:09,320 --> 00:34:12,823
to another group of blackcaps that haven't moved all year.
572
00:34:13,730 --> 00:34:16,793
These blackcaps don't migrate at all.
573
00:34:21,630 --> 00:34:25,130
A researcher at the Complutense University of Madrid,
574
00:34:25,130 --> 00:34:27,920
Javier Perez Tris studies the relationship
575
00:34:27,920 --> 00:34:29,870
between these sedentary blackcaps
576
00:34:29,870 --> 00:34:31,670
and the thousands of migrating birds
577
00:34:31,670 --> 00:34:33,223
that meet here each winter.
578
00:34:34,950 --> 00:34:37,510
Even though they're all part of the same species,
579
00:34:37,510 --> 00:34:41,026
their cohabitation is not always peaceful.
580
00:34:41,026 --> 00:34:43,359
(mumbles)
581
00:34:45,940 --> 00:34:47,373
So they arrived already.
582
00:34:49,360 --> 00:34:51,020
This must be the migratory blackcaps
583
00:34:51,020 --> 00:34:53,670
because they serve it at seldom use by the residents.
584
00:34:54,820 --> 00:34:56,110
If you look at the forest,
585
00:34:56,110 --> 00:34:59,147
this is the habitat of the resident population of blackcaps
586
00:34:59,147 --> 00:35:01,653
in the Jakarta area.
587
00:35:02,940 --> 00:35:06,520
The migrants are arriving to the place like in high numbers
588
00:35:06,520 --> 00:35:09,580
so the amount of blackcaps is 20 times as much
589
00:35:09,580 --> 00:35:11,833
as they are in Summer.
590
00:35:13,200 --> 00:35:15,640
The interesting thing is that the juvenile migrants
591
00:35:15,640 --> 00:35:18,040
they are apparently pushed outside the forest
592
00:35:18,040 --> 00:35:21,150
to the shrub lands like these ones that you see here.
593
00:35:21,150 --> 00:35:24,530
So this is an open habitat and they have to move in the open
594
00:35:24,530 --> 00:35:26,600
between the bushes and this is risky for them.
595
00:35:26,600 --> 00:35:29,850
So they get exposed to (mumbles) and all the radiators
596
00:35:29,850 --> 00:35:30,900
that can attack them.
597
00:35:35,060 --> 00:35:36,858
While the youngest migratory blackcaps
598
00:35:36,858 --> 00:35:39,440
are pushed to the edge of the forest,
599
00:35:39,440 --> 00:35:42,803
the adults claimed territory beneath the cork oaks.
600
00:35:48,720 --> 00:35:52,350
Javier Perez Tris can spot morphological differences
601
00:35:52,350 --> 00:35:54,930
that exist between the migratory birds
602
00:35:54,930 --> 00:35:57,667
and the sedentary ones in a single glance.
603
00:36:04,580 --> 00:36:05,830
12.5, 1.5, 5.
604
00:36:10,730 --> 00:36:12,660
This is a migrant for sure.
605
00:36:12,660 --> 00:36:14,960
So the main difference between the two birds,
606
00:36:14,960 --> 00:36:17,290
between the migrant and and the resident
607
00:36:17,290 --> 00:36:20,880
is the wings of the migrants are much longer,
608
00:36:20,880 --> 00:36:25,550
they are more pointy and the tail is comparatively shorter.
609
00:36:27,000 --> 00:36:29,180
The legs are typically shorter also.
610
00:36:29,180 --> 00:36:31,970
I mean this is very good at migrating
611
00:36:31,970 --> 00:36:35,640
and then the migrants typically have a lighter structure
612
00:36:35,640 --> 00:36:38,980
so you don't carry so much load.
613
00:36:38,980 --> 00:36:43,850
The residents, they have long legs, bigger bills,
614
00:36:43,850 --> 00:36:48,020
rounded wings better for maneuvering in those vegetation.
615
00:36:48,020 --> 00:36:50,000
At the same time by being bigger,
616
00:36:50,000 --> 00:36:54,050
we think that they can afford confrontation (mumbles)
617
00:36:54,050 --> 00:36:55,380
with the migrants that come from the north
618
00:36:55,380 --> 00:36:57,080
and exploit the same territories,
619
00:36:57,080 --> 00:36:59,640
they use for the whole year.
620
00:36:59,640 --> 00:37:03,910
Probably they are not very (laughing)
621
00:37:03,910 --> 00:37:05,460
I mean very fond of each other.
622
00:37:08,880 --> 00:37:10,539
The birds that coexist
623
00:37:10,539 --> 00:37:12,480
in this Andalusian forest
624
00:37:12,480 --> 00:37:14,830
prove that different behaviors can be present
625
00:37:14,830 --> 00:37:18,023
in creatures that are technically the same species.
626
00:37:25,620 --> 00:37:28,503
Some of the blackcaps decide to go a lot further.
627
00:37:29,640 --> 00:37:33,200
These tireless travelers cross the Strait of Gibraltar
628
00:37:33,200 --> 00:37:36,100
and continue until they reach the Magreb countries
629
00:37:36,100 --> 00:37:37,783
or even Western Africa.
630
00:37:39,800 --> 00:37:42,800
All these birds chose to leave at the right time
631
00:37:42,800 --> 00:37:46,313
as winter has now taken over all of northern Europe.
632
00:37:51,618 --> 00:37:54,940
(lively music)
633
00:37:54,940 --> 00:37:56,990
In southern England,
634
00:37:56,990 --> 00:37:59,223
morning frost or more and more frequent.
635
00:38:02,650 --> 00:38:05,290
The forests and hedges now have little to offer
636
00:38:05,290 --> 00:38:06,173
to passerines.
637
00:38:08,500 --> 00:38:11,400
A blackcaps chances of survival are very low
638
00:38:11,400 --> 00:38:13,423
in such hostile environments.
639
00:38:16,670 --> 00:38:21,200
Yet against all logic, some blackcaps take the risk
640
00:38:21,200 --> 00:38:23,293
of hibernating in these latitudes.
641
00:38:27,130 --> 00:38:29,160
In Chilbolton in Hampshire,
642
00:38:29,160 --> 00:38:32,193
one man is lucky enough to have witnessed this himself.
643
00:38:34,570 --> 00:38:36,930
A bird lover since he was a boy,
644
00:38:36,930 --> 00:38:40,010
Glynne Evans has noticed this mysterious phenomenon
645
00:38:40,010 --> 00:38:42,083
growing in scale over the years.
646
00:38:46,760 --> 00:38:51,070
50 years ago we never used to see blackcaps in gardens
647
00:38:51,070 --> 00:38:56,070
in winter in England and that's comparing with 25 blackcaps
648
00:38:58,220 --> 00:39:02,260
that I've encountered in the garden this winter.
649
00:39:02,260 --> 00:39:05,300
I mean always these things are very fascinating.
650
00:39:05,300 --> 00:39:07,770
You get these strange changes that take place
651
00:39:07,770 --> 00:39:09,063
and one wonders why.
652
00:39:14,380 --> 00:39:16,540
The presence of these wintering blackcaps
653
00:39:16,540 --> 00:39:17,493
is a mystery.
654
00:39:19,090 --> 00:39:20,823
Why are there numbers rising?
655
00:39:22,170 --> 00:39:24,003
How did they survive the winter?
656
00:39:25,960 --> 00:39:29,270
Glynne is part of a vast network of voluntary observers
657
00:39:29,270 --> 00:39:33,210
that work in collaboration with scientists from the BTO,
658
00:39:33,210 --> 00:39:35,483
the British Trust for Ornithology.
659
00:39:36,370 --> 00:39:38,840
Greg Conway is the Program Coordinator
660
00:39:38,840 --> 00:39:42,510
and he has several explanations for the birds behavior.
661
00:39:42,510 --> 00:39:44,310
The wings distribution of blackcap
662
00:39:44,310 --> 00:39:47,720
is increased by it was 77%.
663
00:39:47,720 --> 00:39:49,800
We know that the climate has changed
664
00:39:49,800 --> 00:39:51,940
quite considerably since the 1980s.
665
00:39:51,940 --> 00:39:53,890
We've got substantial warming
666
00:39:53,890 --> 00:39:56,360
across pretty much the whole the British Isles.
667
00:39:56,360 --> 00:39:57,550
That could be at a point now
668
00:39:57,550 --> 00:39:59,940
where that makes it more suitable for the birds.
669
00:39:59,940 --> 00:40:01,970
They can survive better in these areas
670
00:40:01,970 --> 00:40:03,600
but there are other factors as well.
671
00:40:03,600 --> 00:40:06,150
I mean in the British Isles people really love the birds
672
00:40:06,150 --> 00:40:10,420
so we find between 48 maybe 55 percent of households
673
00:40:10,420 --> 00:40:11,720
actually put food out for birds
674
00:40:11,720 --> 00:40:13,320
during the course of the winter.
675
00:40:13,320 --> 00:40:17,330
So that's a substantial resource for many wintering birds.
676
00:40:17,330 --> 00:40:19,913
(lively music)
677
00:40:21,710 --> 00:40:22,550
Great Britain
678
00:40:22,550 --> 00:40:25,873
is currently Europe's biggest bird food consumer by far.
679
00:40:38,740 --> 00:40:39,980
The sale of bird food
680
00:40:39,980 --> 00:40:42,620
is a multi-million Euro annual business
681
00:40:42,620 --> 00:40:44,673
that shows no signs of slowing.
682
00:40:46,420 --> 00:40:48,790
It's encouraged by the country's garden stores
683
00:40:48,790 --> 00:40:49,983
and supermarkets.
684
00:40:52,160 --> 00:40:56,720
This winter, some 60, 000 tons of seeds, fat balls,
685
00:40:56,720 --> 00:41:00,133
dried insects and fruit were offered to the birds.
686
00:41:02,130 --> 00:41:04,370
But while these industrial food products
687
00:41:04,370 --> 00:41:06,290
are a joy for the passerines.
688
00:41:06,290 --> 00:41:08,040
Ornithologist wishing to observe
689
00:41:08,040 --> 00:41:10,340
specific types of birds in their gardens
690
00:41:10,340 --> 00:41:12,603
are forced to cook up something of their own.
691
00:41:14,690 --> 00:41:17,040
That's just what Glyne Evans does,
692
00:41:17,040 --> 00:41:21,250
having perfected his very own recipe for blackcaps.
693
00:41:21,250 --> 00:41:23,730
Blackcaps are insectivores birds
694
00:41:23,730 --> 00:41:27,050
and the commercial fat balls are rather hard for them.
695
00:41:27,050 --> 00:41:30,020
So I try and make a match of it a bit softer.
696
00:41:30,020 --> 00:41:33,120
Rather like this which appears quite hard.
697
00:41:33,120 --> 00:41:35,760
But if I stick a spoon in
698
00:41:35,760 --> 00:41:40,260
you see that it's much softer than the hard things
699
00:41:40,260 --> 00:41:43,843
that we get from commercial suppliers.
700
00:41:46,600 --> 00:41:48,620
With an increasingly mild weather
701
00:41:48,620 --> 00:41:51,210
and an abundance of available food,
702
00:41:51,210 --> 00:41:54,883
the blackcap is now able to survive the English winter.
703
00:42:00,180 --> 00:42:03,040
Yet one question remains,
704
00:42:03,040 --> 00:42:04,940
are these blackcaps the same ones
705
00:42:04,940 --> 00:42:06,880
we see in England in summer?
706
00:42:06,880 --> 00:42:09,713
Or as some believe, are they from somewhere else?
707
00:42:11,090 --> 00:42:13,900
Benjamin Van Doren from Oxford University
708
00:42:13,900 --> 00:42:16,973
hopes to have the answer to that question soon.
709
00:42:18,780 --> 00:42:23,090
Last winter, he fit about 30 blackcaps with geo locators
710
00:42:23,090 --> 00:42:25,153
to find out where they spend the summer.
711
00:42:26,240 --> 00:42:28,200
It's crucial that the young scientist
712
00:42:28,200 --> 00:42:31,333
retrieves as many of his geo locators as possible.
713
00:42:33,850 --> 00:42:35,580
He meets up with Glyne Evans,
714
00:42:35,580 --> 00:42:38,513
who rigged his garden with capture nets for the occasion.
715
00:42:39,750 --> 00:42:42,320
You have information from ringing blackcaps
716
00:42:42,320 --> 00:42:45,070
but there have only been a handful of recoveries
717
00:42:45,070 --> 00:42:48,860
of these birds that have spent the winter in Britain
718
00:42:48,860 --> 00:42:50,360
and have been captured elsewhere.
719
00:42:50,360 --> 00:42:52,730
So these blackcaps could be going elsewhere
720
00:42:52,730 --> 00:42:54,560
or could be staying in the UK
721
00:42:54,560 --> 00:42:57,750
or could be doing other things that we would have no idea
722
00:42:57,750 --> 00:43:00,930
without tracking them individually with geo locators.
723
00:43:00,930 --> 00:43:04,050
Last winter we deployed 36 geo locators
724
00:43:04,050 --> 00:43:08,113
we'll hope to get back at least 12%, 15% if we can.
725
00:43:11,080 --> 00:43:12,950
Of the 36 blackcaps ringed
726
00:43:12,950 --> 00:43:14,950
with geo locators in this garden,
727
00:43:14,950 --> 00:43:17,053
only three have returned this winter.
728
00:43:20,610 --> 00:43:23,363
But Benjamin Van Doren can finally smile.
729
00:43:25,070 --> 00:43:28,773
The data he's collected reveals something extraordinary.
730
00:43:30,310 --> 00:43:34,740
The first bird that we captured left the UK on March 29
731
00:43:34,740 --> 00:43:36,808
and then we can see it spent the summer months
732
00:43:36,808 --> 00:43:40,870
in eastern France and worked its way back to the UK
733
00:43:40,870 --> 00:43:42,393
by early November.
734
00:43:43,300 --> 00:43:45,380
Is very weird for a bird to do.
735
00:43:45,380 --> 00:43:46,930
I don't know any other examples of birds
736
00:43:46,930 --> 00:43:50,910
that in the northern hemisphere migrated south
737
00:43:50,910 --> 00:43:53,260
for the summer and north for the winter.
738
00:43:53,260 --> 00:43:56,780
The second bird, it went all the way to southern Germany
739
00:43:56,780 --> 00:43:59,260
potentially the Western Czech Republic.
740
00:43:59,260 --> 00:44:00,450
The third bird we caught
741
00:44:00,450 --> 00:44:02,500
it seems to have gone to a similar location,
742
00:44:02,500 --> 00:44:05,150
potentially a little bit further south towards Italy.
743
00:44:07,260 --> 00:44:09,170
The data collected from the three birds
744
00:44:09,170 --> 00:44:10,173
is baffling.
745
00:44:12,830 --> 00:44:16,620
In autumn when the majority of birds headed south,
746
00:44:16,620 --> 00:44:20,620
these three blackcaps migrated towards the Northwest.
747
00:44:20,620 --> 00:44:23,900
Global warming and an abundance of food from humans
748
00:44:23,900 --> 00:44:26,593
allowed them to survive the English winter.
749
00:44:31,520 --> 00:44:32,830
It seems as though England
750
00:44:32,830 --> 00:44:35,123
is becoming a new migratory destination.
751
00:44:49,376 --> 00:44:52,126
(dramatic music)
752
00:44:53,120 --> 00:44:54,690
As soon as winter ends,
753
00:44:54,690 --> 00:44:57,303
the blackcaps prepare for the return trip.
754
00:44:59,711 --> 00:45:02,420
The first to go are those that spent winter
755
00:45:02,420 --> 00:45:03,703
in the United Kingdom.
756
00:45:07,420 --> 00:45:08,460
In early March,
757
00:45:08,460 --> 00:45:11,240
the blackcaps that spent winter in western Africa
758
00:45:11,240 --> 00:45:13,810
rejoin the birds from the Iberian Peninsula
759
00:45:13,810 --> 00:45:16,053
that are already in route towards the north.
760
00:45:20,437 --> 00:45:21,660
Three weeks later,
761
00:45:21,660 --> 00:45:25,013
these birds reach the foothills of the Pyrenees Mountains.
762
00:45:30,230 --> 00:45:31,660
Their arrival coincides
763
00:45:31,660 --> 00:45:34,863
with the flowering of the willow trees and wild cherries.
764
00:45:37,620 --> 00:45:39,430
With few insects around,
765
00:45:39,430 --> 00:45:43,323
the blackcaps adapt once again filling up on nectar.
766
00:45:45,160 --> 00:45:47,480
Less than six weeks after leaving Andalusia,
767
00:45:47,480 --> 00:45:52,200
the first migratory birds arrive at their destination.
768
00:45:52,200 --> 00:45:55,740
The blackcaps that nest in France, Belgium and Switzerland
769
00:45:55,740 --> 00:45:56,943
are already home.
770
00:46:01,690 --> 00:46:05,010
In the (mumbles) Valley in the heart of the Austrian Alps,
771
00:46:05,010 --> 00:46:08,463
blackcaps returned from every possible direction.
772
00:46:17,390 --> 00:46:21,123
Miriam Leidvogel is waiting for them here in the forest.
773
00:46:23,200 --> 00:46:26,130
This valley is in the heart of the migratory divide
774
00:46:26,130 --> 00:46:30,193
making it a great location for recapturing hybrid blackcaps.
775
00:46:34,220 --> 00:46:36,920
Birds from the southwest, the southeast
776
00:46:36,920 --> 00:46:41,325
and maybe even from England all come here for mating season.
777
00:46:41,325 --> 00:46:44,750
(birds chirping)
778
00:46:44,750 --> 00:46:47,369
It's now the male's turn to sing.
779
00:46:47,369 --> 00:46:50,119
(birds chirping)
780
00:46:51,590 --> 00:46:53,943
New couples form every day.
781
00:46:56,900 --> 00:46:59,333
Soon the first eggs will appear.
782
00:47:01,510 --> 00:47:05,740
Since returning the blackcaps have once again become diurnal
783
00:47:05,740 --> 00:47:08,793
and taken up a high protein insect based diet.
784
00:47:14,430 --> 00:47:17,573
This is exactly what their fledglings need to grow quickly.
785
00:47:25,390 --> 00:47:28,150
Males and females must also regularly remove
786
00:47:28,150 --> 00:47:30,560
the excrements produced by their chicks
787
00:47:30,560 --> 00:47:33,953
which is conveniently wrapped in small airtight packets.
788
00:47:37,168 --> 00:47:39,668
(light music)
789
00:47:51,300 --> 00:47:54,890
Joseph Hemburger, the valleys leading ornithologist,
790
00:47:54,890 --> 00:47:56,253
is already hard at work.
791
00:48:03,250 --> 00:48:06,760
The night before Miriam Leidvogel spotted a male
792
00:48:06,760 --> 00:48:08,913
that seemed to have a Geo locator.
793
00:48:10,520 --> 00:48:12,590
Capturing the bird and retrieving the data
794
00:48:12,590 --> 00:48:15,883
from its geo locator is crucial for the ornithologists.
795
00:48:17,840 --> 00:48:21,610
To be successful, they'll need every bit of their know-how
796
00:48:21,610 --> 00:48:23,383
and also a little luck.
797
00:48:26,017 --> 00:48:26,873
[Female translator] How's it going?
798
00:48:26,873 --> 00:48:28,560
There's a male in the net,
799
00:48:28,560 --> 00:48:29,393
I'll go, get him.
800
00:48:29,393 --> 00:48:30,713
[Female Translator] Wonderful.
801
00:48:34,581 --> 00:48:38,450
Yes, this one was ringed with this geo locator a year ago.
802
00:48:38,450 --> 00:48:40,570
Maybe he went to Africa or something,
803
00:48:40,570 --> 00:48:41,770
we're about to find out.
804
00:48:42,630 --> 00:48:44,323
Let's remove the geo locator.
805
00:48:50,600 --> 00:48:55,570
The bird is okay.
806
00:48:55,570 --> 00:48:56,573
We can release him.
807
00:49:01,350 --> 00:49:04,150
Now to visualize exactly where he was located,
808
00:49:04,150 --> 00:49:06,400
we need to download the data to the computer.
809
00:49:09,020 --> 00:49:11,830
This data, the very latest of the season,
810
00:49:11,830 --> 00:49:16,193
is being added to 66 other findings taken all over Europe.
811
00:49:19,890 --> 00:49:23,693
The blackcaps migratory map is slowly starting to change.
812
00:49:30,917 --> 00:49:34,330
[Female Translator] The data seems okay.
813
00:49:34,330 --> 00:49:35,390
The information we need
814
00:49:35,390 --> 00:49:38,813
to trace this migratory blackcaps itinerary is all here.
815
00:49:41,320 --> 00:49:43,780
What we can see is exactly what we wanted to know
816
00:49:46,040 --> 00:49:47,550
which is that the hybrid birds
817
00:49:47,550 --> 00:49:50,233
do indeed follow intermediate itineraries.
818
00:49:52,800 --> 00:49:55,160
They don't follow the east or west trajectories
819
00:49:55,160 --> 00:49:56,823
around the Mediterranean Sea,
820
00:49:58,070 --> 00:49:59,720
they go straight down the middle.
821
00:50:01,690 --> 00:50:03,610
What the data proves with certainty
822
00:50:03,610 --> 00:50:06,830
is that it's possible for a bird to fly over the Alps,
823
00:50:06,830 --> 00:50:09,970
the Mediterranean Sea and the Sahara Desert
824
00:50:10,870 --> 00:50:12,870
before returning unharmed.
825
00:50:12,870 --> 00:50:15,423
That was not obvious before we had this data.
826
00:50:16,330 --> 00:50:19,480
So for us, the blackcap is particularly interesting
827
00:50:19,480 --> 00:50:21,290
because it has an immense repertoire
828
00:50:21,290 --> 00:50:23,540
of possible migratory routes.
829
00:50:23,540 --> 00:50:26,630
It easily adapts to different environmental conditions
830
00:50:26,630 --> 00:50:29,150
and it can overcome numerous barriers.
831
00:50:29,150 --> 00:50:30,740
This is a very robust bird
832
00:50:30,740 --> 00:50:34,010
that quickly adapts to any new territory for example,
833
00:50:34,010 --> 00:50:36,750
those that survive winter on the British Isles.
834
00:50:36,750 --> 00:50:39,803
I wholeheartedly believe this is the bird of the future.
835
00:50:43,270 --> 00:50:45,090
These dedicated researchers
836
00:50:45,090 --> 00:50:48,210
have learned that the blackcap shows complex behavior
837
00:50:48,210 --> 00:50:50,853
and evolving migratory skills.
838
00:50:53,800 --> 00:50:56,160
Its incredible ability to adapt
839
00:50:56,160 --> 00:51:00,900
allows it to modify its itinerary, change its diet
840
00:51:00,900 --> 00:51:04,033
and succeed where many other species are failing.
841
00:51:06,510 --> 00:51:08,900
It's one of the few migratory passerines
842
00:51:08,900 --> 00:51:10,753
whose population is growing.
843
00:51:13,450 --> 00:51:15,910
By migrating in the opposite direction
844
00:51:15,910 --> 00:51:17,700
and spending winter in England,
845
00:51:17,700 --> 00:51:20,020
it demonstrates an amazing defiance
846
00:51:20,020 --> 00:51:22,003
in the face of human activity.
847
00:51:24,750 --> 00:51:28,210
If the future of biodiversity belongs to the animals
848
00:51:28,210 --> 00:51:30,940
with the best capacity for adaptation,
849
00:51:30,940 --> 00:51:33,813
the blackcap is certain to be among them.
850
00:51:35,710 --> 00:51:38,293
(lively music)
67246
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