>> Chang: TONIGHT JOIN US LIVE FOR AN UNPRECEDENTED JOURNEY INTO SPRING AND THE STUNNING CHANGES IT BRINGS TO THE WORLD AROUND US.

WE'LL BE EXPLORING ALL SORTS OF SPRING AWAKENINGS, FROM COAST TO COAST.

L IN THE ALLEGHENY MOUNTAINS WHERE RESEARCHERS ARE CHECKING ON THE HEALTH OF THE BEAR POPULATION S WH ONE CUB AT A TIME, TO THE FLORIDA EVERGLADES WHERE ALLIGATORS ARE ON THE PROWL FOR NATURE'S BOUNTY.

H WE'LL INTRODUCE YOU TO THE ROLE YOU CAN PLAY AS A CITIZEN ALLIGATORS ARE ON THE PLOW FO SCIENTIST, HELPING RESEARCHERS TRACK THE SECRET LIFE OF BIRDS.

AND OVER IN MAINE, ONE MOTHER IS ABOUT TO BRING NEW LIFE INTO THE WORLD.

JOIN US FOR A LIVE DIVE INTO THE SCIENCE OF SPRING AS WE WATCH IT D. UNFOLD ACROSS AMERICA.

HE SCIENCE OF SPRING AS WE WATCH IT UNFOLD ACROSS AME THIS IS "AMERICAN SPRING LIVE."

>> Chang: WELCOME TO "AMERICAN SPRING LIVE."

AND I'M JUJU CHANG COMING TO YOU LIVE FROM THE SIERRA NEVADA MOUNTAINS IN CALIFORNIA.

AND AS YOU CAN SEE BEHIND ME, WE'RE HAVING SOME WEATHER MOVING IN, IN THE FORM OF DARK CLOUDS.

WE MAY EVEN GET SOME RAIN, BUT THAT'S MOTHER NATURE.

IT IS STILL A BREATHTAKING VIEW OF SEQUOIA NATIONAL PARK.

AND TONIGHT AND FOR THE NEXT TWO NIGHTS, WE'LL BE CHECKING IN ACROSS THE COUNTRY WITH SCIENTISTS, RESEARCHERS AND SCORES OF NATURE ENTHUSIASTS, LIKE YOU, DIVING INTO THE SCIENCE OF SPRING TO FIND OUT WHAT'S HAPPENING AND WHY.

OUR THEME TONIGHT IS BIRTH AND REBIRTH, AND JOINING ME ON THIS ADVENTURE, NO ONE BETTER THAN WORLD-RENOWNED BIOLOGIST DR. THOR HANSON.

ADVENTURE, NO ONE BET THOR HANSON.

HEY, THOR, MY NEW FRIEND.

>> HEY, JUJU.

WO >> Chang: YOU KNOW, SPRING IS SPRINGING OUT ALL OVER US.

>> IT IS, AND IT'S AN EXCITING TIME TO BE A SCIENTIST, AS WELL.

H IT'S A GREAT TIME TO DO RESEARCH, BECAUSE SPRING IS FULL OF CRITICAL EVENTS IN THE LIVES OF PLANTS AND ANIMALS.

EVERYWHERE YOU LOOK, SPRING IS A SEASON OF NEW LIFE.

>> Chang: THAT'S TRUE, THOR, AND SPEAKING OF NEW LIFE, WE HAVE A VERY SPECIAL SPRINGTIME EVENT LOOK, SPRING IS THAT'S BEEN UNFOLDING.

WE'RE REALLY EXCITED TO SHARE IT WITH YOU.

D IT'S BEEN HAPPENING ALL THE WAY ACROSS THE COUNTRY, IN WASHINGTON, MAINE.

LET'S GO THERE.

YOU CAN HEAR THE LAMBS.

THEY ARE BABY LAMBS THAT ARE BEING BORN PRETTY MUCH EVERY DAY AROUND THE CLOCK ON MEADOWCROFT FARM.

AND WE WERE THERE AT THE VERY MOMENT THAT SHEEP FARMER NANNE KENNEDY HELPED DELIVER HER W LATEST.

[BLEATING] >> SHE'S GETTING READY TO LAY DOWN AND START PUSHING.

SHE'S CUED THE BABY UP INTO THE BIRTH CANAL.

SHE'S JUST IN PROCESS.

THE BEST POSITION FOR ME, SINCE SHE'S FUSSING AND TRYING TO GET UP, IS TO PUT MY FOOT UNDERNEATH HER LOWER SHOULDER.

BUT YOU CAN SEE SHE'S STARTING TO, UM, YOU KNOW, STRESS A LITTLE BIT, SO, I'M JUST GONNA...

THERE WE GO.

AND NOW HERE COMES THE HEAD.

THAT'S A NICE BIG BABY.

THAT'S RIGHT, PUSH ON ME, GIRL.

THAT'S RIGHT, MY MUFFIN.

OKAY.

NICE BIG BABY.

NICE BIG BABY.

NICE BIG BABY.

COME ON, THERE YOU GO.

THAT'S IT.

BY.

THERE YOU GO-- FIRST BREATH.

LUNGS HAVE BEEN...

THERE WE GO.

I'M GOING TO LET HER FINISH.

AND...

I'M GO [BLEATING, DOG BARKING] THERE YOU GO, SWEETIE PIE.

HERE YOU GO.

THAT WAS A BIG HEAD AND KIND OF A TOUGH GO.

THERE WE GO.

AND THAT'S PROBABLY A 12 OR 13-POUND LAMB.

CLOSER TO 13.

[BLEATING] POUND YEAH, THAT WAS JUST A TINY BIT STRESSFUL.

UH, I'M GOING TO LET THEM MOTHER-UP BEFORE I INTERFERE.

SOON AS THEY DEFINITELY HAVE CREATED A BOND, I WILL GO IN THERE AND SNIP HIS UMBILICAL CORD TO ABOUT AN INCH.

AND S I WILL DIP IT WITH IODINE, 7% TINCTURE.

I WILL STRIP THE TEATS IF THEY NEED TO BE STRIPPED, 'CAUSE THEY HAVE A LITTLE WAX PLUG, AND I HAVE TO MAKE SURE THAT THE MILK IS FLOWING, AND THEN I WILL MAKE SURE HE GETS A GOOD SIP.

BABY IS REALLY FOCUSED ON JUST TRYING TO MOVE THROUGH KIND OF ROUGH TERRAIN.

[BLEATING] >> COME ON, KIDS!

>> NOT SUPER EASY FOOTING RIGHT THERE FOR SOMEONE THAT STARTED WALKING FIVE MINUTES AGO.

[LAUGHING] YOU CAN SEE HE'S A LITTLE SHIVERY.

THEY'RE BORN WITHOUT BROWN FAT, SO THEY DON'T HAVE ANY WAY OF KEEPING THEMSELVES WARM.

THEY HAVE NO WAY TO GENERATE HEAT UNTIL THEY GET SOME OF THAT COLOSTRUM IN THEIR BELLY.

IT'S EXTREMELY HIGH IN ENERGY, AND AS SOON AS THEY GET THAT, THEY WILL BASICALLY HAVE FUEL IN THEIR TANK TO GET THEIR ENGINES GOING.

AND THERE HE IS.

>> HI, KIDS!

>> WELCOME, BABY.

WELCOME, SPRING!

>> YAY!

RIGHT?

[LAUGHING] [BLEATING] >> Chang: AND JOINING US NOW LIVE, YOU CAN SEE BABY LAMBS THAT ARE NURSING.

THIS IS A VERY BUSY, VERY CROWDED, VERY LOUD LAMB NURSERY, AND WE'RE BEING JOINED BY SHEEP FARMER NANNE KENNEDY.

NANNE, WHAT WAS IT LIKE?

WE WATCHED YOU HELP DELIVER A LAMB BABY.

[BLEATING] >> OH, THOUGH... HI, JUJU.

IT WAS A LITTLE STRESSFUL, I'LL BE HONEST WITH YOU, BUT IT WAS PROBABLY NOT AS STRESSFUL FOR ME UL AS IT WAS FOR HER.

THAT BABY ENDED UP BEING 15 AND A HALF POUNDS.

UM, I'VE BEEN DOING THIS FOR ED UP BEING ALMOST 40 YEARS, AND, UH, IT NEVER...

IT NEVER GETS... N IT NEVER LOSES ITS MIRACLE.

UM, EVERY BIRTH CAN HAVE COMPLICATIONS, BUT, UM, NOT MANY OF THEM DO.

E I DON'T LIKE TO INTERVENE, BUT I'M GLAD I DID FOR THAT ONE IN PARTICULAR, 'CAUSE IT'S A BEAUTIFUL BIG BOY, AND HE'S DOING GREAT, AND SO ARE ALL THE MOMS.

THESE GUYS ARE ACTUALLY RAISED FOR...

PRIMARILY FOR WOOL, NOT...

UH, FOR FINE WOOL, NOT MEAT BREEDS OR CARPET BREEDS OR DAIRY BREEDS.

THEY WILL HAVE A LONG AND HAPPY LIFE, UH, GETTING AN ANNUAL HAIRCUT AND, UH, GRAZING ON IMPROVED SUMMER GRASS.

UM, THEY... LI IT'S NOT REALLY ROCKET SCIENCE, BUT HONESTLY, THERE'S A LOT MORE TO IT THAN YOU MIGHT THINK.

I NEED TO CONSTANTLY KEEP WATCH TO MAKE SURE THAT THEY'RE OKAY, NK.

UH, TO KNOW WHAT IT LOOKS LIKE WHEN THEY'RE NOT, AND TO KNOW HOW TO FIX IT, UH, IF-IF SOMETHING GOES WRONG.

O SO...

SO THERE YOU HAVE IT.

AND THEY ARE HEALTHY AND WELL AND DOING GREAT.

[BLEATING] >> Chang: OH, THAT'S FANTASTIC, NANNE.

WE'RE SO HAPPY FOR YOU.

AND I HAVE TO SAY, LAMB BABIES ARE LIKE HUMAN BABIES.

THEY CAN'T FIGURE OUT WHEN TO SLEEP, SO NANNE'S BEEN SPENDING A LOT OF SLEEPLESS NIGHTS.

NOW, EARLIER, NANNE TALKED ABOUT COLOSTRUM, AND I KNOW THAT HUMAN BREAST MILK CONTAINS COLOSTRUM.

THAT'S BASICALLY WHAT SHE'S TALKING ABOUT, RIGHT, THOR?

>> YES, IT'S THE SAME IDEA.

COLOSTRUM IS REALLY SUPERCHARGED MOTHER'S MILK.

M NOT ONLY EXTRA NUTRITIOUS, BUT ALSO FILLED WITH ANTIBODIES FROM THE MOTHER THAT WILL HELP KEEP THAT LITTLE LAMB HEALTHY.

>> Chang: AND THERE'S NOTHING MORE ICONIC ABOUT SPRING THAN A BABY LAMB, BUT WHAT'S THE SCIENCE BEHIND WHY SO MANY OF THESE BABY ANIMALS ARE BORN IN THE SPRINGTIME?

>> WELL, WE'LL BE TALKING A LOT ABOUT TIMING, JUJU.

IM UH, WITH ALL THE NEW PLANT GROWTH OUT THERE, IT'S THE PERFECT TIME TO DO SOMETHING THAT DEMANDS A LOT OF ENERGY, LIKE RAISING LAMBS.

>> Chang: YEAH, BASICALLY, AND YOU CAN SEE HOW BUSY IT IS THERE.

N THERE IS, UM, SO MUCH ACTIVITY.

WE'LL BE CHECKING BACK IN, IN MAINE LATER IN BROADCAST.

>> OKAY.

>> Chang: BUT RIGHT NOW, I WANT C TO INTRODUCE YOU TO ANOTHER MEMBER OF OUR SCIENCE TEAM WHO'S BEEN SPENDING THE LAST FEW DAYS EXPLORING SEQUOIA NATIONAL PARK BEHIND US.

PHIL TORRES IS AN ENTOMOLOGIST.

THAT IS A SCIENTIST, LIKE YOU, WHO STUDIES INSECTS.

AND HE'S WAY BACK THERE, SPENDING TIME EXPLORING.

LET'S CHECK IN ON SEEING WHAT HE'S FOUND.

PHIL?

>> HELLO FROM WAY BACK HERE.

NOW, BELIEVE IT OR NOT, RIGHT NOW, I AM INSIDE A BURNED-OUT GIANT SEQUOIA TREE.

SEE IF I CAN MAKE MY WAY OUT OF THERE.

NOW, LOOK AT THIS THING.

UNLIKE THOSE NEWBORN BABY LAMBS WE JUST SAW, THIS TREE IS PROBABLY 1,000 TO 2,000 YEARS OLD, AND IF YOU LOOK UP THERE, THE AMAZING PART-- YES, IT'S CHARRED OUT INSIDE-- BUT IT IS STILL ALIVE.

HOW INCREDIBLE IS NATURE?

NOW, WHILE I'M OUT HERE EXPLORING THE SEQUOIA GROVE, I'M HOW INCREDIBLE IS NATU ALSO GOING TO BE PRESENTING TO YOU GUYS SOME CITIZEN SCIENCE PROJECTS.

THESE ARE PROJECTS THAT YOU CAN DO AT HOME, IN YOUR YARD, IN THE PARK DOWN THE STREET, AND CONTRIBUTE TO REAL SCIENCE.

AND IF YOU WANT TO LEARN MORE ABOUT THESE, CHECK OUT OUR PBS NATURE FACEBOOK PAGE WHERE WE WILL HAVE LINKS TO ALL SORTS OF THESE PROJECTS THAT ARE ALL JUST ABSOLUTELY AMAZING.

AND WHILE YOU'RE ON OUR H FACEBOOK, I WANT TO SEE SOME COMMENTS.

I WANT TO SEE SOME QUESTIONS.

AND AT THE END OF THIS HOUR, WE'RE GONNA BE ANSWERING SOME OF THOSE QUESTIONS LIVE ON AIR.

NOW, THERE'S ONE MORE THING I GOT TO SHOW YOU BEFORE WE GO.

ONS LIVE ON AIR.

YOU KNOW HOW THEY SAY "SPRING IS IN THE AIR"?

WELL, THIS IS FROM A GIANT SEQUOIA, AND-- WAIT FOR IT-- THAT IS POLLEN.

SPRING IS LITERALLY IN THE AIR OUT HERE.

BACK TO YOU, GUYS.

>> Chang: OH, MY GOSH, I'M GOING TO SNEEZE... >> I DID.

>> Chang: ...JUST BY WATCHING THAT HAPPEN.

E SO WE KNOW, THOR, THAT THE SEASONS CHANGE BECAUSE THE DAYS GET LONGER AND COLDER, OR WARMER, RATHER.

AND POETS HAVE BEEN WRITING ABOUT IT FOR GENERATIONS.

>> MM-HMM.

>> Chang: AND YET, SCIENCE CAN DO SOME EXPLAINING, TOO.

>> SURE.

WELL, ALL OF THIS SPRING ACTIVITY REALLY BOILS DOWN TO ONE THING-- THE EARTH IS TILTED ON ITS AXIS.

AND OUR HEMISPHERE, THE NORTHERN HEMISPHERE, IS BEGINNING TO FACE THE SUN DIRECTLY AT THIS TIME OF THE YEAR, IN SPRINGTIME.

AND IT'S JUST LIKE WARMING YOUR HANDS AT A CAMPFIRE.

EVERYBODY KNOWS YOU DON'T HOLD THEM OUT STRAIGHT IN FRONT OF YOU.

>> Chang: THAT'S RIGHT.

>> YOU FACE THE PALMS OF YOUR D HANDS AT THE FIRE TO-TO, UH, GET ALL THAT DIRECT RADIANT HEAT FROM THE FIRE.

D WELL, IT'S THE SAME WAY WITH SPRINGTIME.

IT IS A BOOST OF RADIANT ENERGY FOR NATURE.

AND YOU CAN SEE THE RESULTS OF THAT, EVEN RIGHT AROUND US HERE ON OUR SET.

UH, FIRST OF ALL, WE'RE STANDING IN THE MIDDLE OF THIS BEAUTIFUL MEADOW FULL OF WILDFLOWERS.

WE'VE GOT PENSTEMONS AND OWL CLOVERS AND ALL SORTS OF DIFFERENT GRASSES, AND WE NOTICED EARLIER THAT RIGHT OVER HERE WE'VE GOT A BEAUTIFUL WE NOTICED EARLIER PATCH OF MILKWEED.

AND MILKWEED IS THE PERFECT FOOD FOR MONARCH BUTTERFLIES.

THOSE LITTLE CATERPILLARS WILL BE NIBBLING ON THOSE LEAVES AND WHEN IT BLOOMS, THE ADULTS CAN NECTAR ON THE BLOSSOMS.

N AND IF WE'RE LUCKY, MAYBE THAT WILL HAPPEN HERE, BUT THE GREAT THING IS, WE DON'T HAVE TO WAIT.

WE DON'T HAVE TO WAIT TO SEE BUTTERFLIES ON OUR MOVIE SET, AND THAT IS BECAUSE RIGHT BEHIND US, WE HAVE THIS LOVELY EXAMPLE OF A CALIFORNIA BUCKEYE TREE, WHICH IS RELATED TO A HORSE CHESTNUT.

AND IT IS IN FULL BLOOM RIGHT NOW, AND IT HAS BEEN FESTOONED WITH PAINTED LADY BUTTERFLIES.

CHECK IT OUT.

>> Chang: AND YOU KNOW, IT USUALLY TAKES MANY WEEKS FOR SPRING TO UNFOLD, BUT THERE IS ONE WAY-- >> I'M CURRENTLY IN THE BEAUTIFUL EASTERN SIERRAS HERE IN CALIFORNIA IN WHAT IS NOW KNOWN INYO NATIONAL FOREST.

I HAVE JUST STARTED A MOUNTAIN BIKE RIDE.

I AM CURRENTLY AT JUST UNDER 8,400 FEET IN ELEVATION, AND ALTHOUGH IT LOOKS LIKE WINTER, IT IS MOST INDEED CERTAINLY SPRING.

AND WHEN IT COMES TO THE EMERGENCE OF SPRING, SPECIFICALLY, IT MOVES FROM A SOUTHERN TO NORTHERN LATITUDE, SO IT MOVES UP THAT GRADIENT.

BUT HERE ON THE MOUNTAIN TODAY HERE IN CALIFORNIA, I'M GONNA BE EXCHANGING THAT LATITUDE FOR ELEVATION.

SO STARTING UP HERE HIGH UP ON THE MOUNTAINS AT 8,400 FEET, I'M LOOKING FOR, AND ALREADY SEEING SIGNS OF SPRING, U WHETHER IT'S WILDLIFE, INCLUDING THE BIRDS, OR THE SMALL MAMMALS THAT I'M ALREADY SEEING TRACKS FOR HERE ON THE SNOW.

AND THE SNOW IS STARTING TO GET A LITTLE BIT SOFT.

IT'S SHOWING SIGNS OF MELTING.

RT AND THE MELTING PROCESS IS REALLY IMPORTANT FOR THE EMERGENCE OF SPRING, BECAUSE UP HERE ON THE MOUNTAIN, AS THE SNOW MELTS, IT TRAVELS DOWNWARD.

AND THAT SLOW MELTING PROCESS IS UN REALLY WHAT PROVIDES THE MOISTURE FOR A LOT OF THE PLANT COMMUNITIES BELOW US AT LOWER ELEVATIONS.

THIS IS ACTUALLY A HUGE ISSUE COMMUNITIES BELOW US FOR CLIMATE CHANGE.

WHEN WE HAVE WARMING TEMPERATURES THAT INCREASE TOO RAPIDLY, THE SNOW MELTS VERY, VERY FAST, AND IT DOESN'T PROVIDE ENOUGH TIME FOR THE SOIL BELOW AT LOWER ELEVATION TO ABSORB THAT MOISTURE, TO ABSORB THAT WATER.

AND AS A RESULT, THAT CREATES ISSUES OF PLANT COMMUNITIES DOWN AT LOWER ELEVATION.

UP HERE, HOWEVER, THERE IS STILL SNOW ON THE GROUND.

MOISTURE'S NOT AN ISSUE TODAY.

IT IS PRETTY COLD, HOWEVER.

SO RIGHT HERE, I HAVE GOT A THERMOMETER, AND I'M GOING TO TEST THE SNOW TEMPERATURE, WHICH WE WOULD EXPECT TO BE BELOW FREEZING BECAUSE IT'S SNOW.

AND EVEN THOUGH IT'S 60 DEGREES FAHRENHEIT IN THE AIR AROUND ME, THE SNOW IS HOVERING JUST AT FREEZING.

SO IT'S 31 DEGREES FAHRENHEIT, JUST OVER ZERO FOR YOU CELSIUS FANS.

AND THE SNOW ITSELF ACTS AS A PRETTY GOOD INSULATOR.

SO GETTING A LITTLE BIT CLOSER DOWN TO THE BOTTOM AT THE SOIL, IT SHOULD BE A TINY BIT COLDER THAN IT IS ON TOP.

SO STICKING THIS THERMOMETER ALL THE WAY DOWN AS FAR AS I CAN, I'VE LOST A DEGREE.

IT IS 30 DEGREES FAHRENHEIT.

AND EVEN THOUGH THE SNOW IS COLD, THE ANIMALS ACTUALLY MAKE USE OF THIS AS A RESOURCE, SO THERE ARE LOTS OF SPECIES THAT ARE SUBNIVEAN, OR SPECIES THAT LIVE BELOW THE SNOW.

AND I'M LIKELY STANDING ON TOP OF SOME REALLY COOL TUNNELS OF SOME MICE OR SOME GROUND SQUIRRELS THAT ARE TRYING TO BASICALLY PROTECT THEMSELVES FROM OTHER SPECIES, OTHER PREDATORS THAT LIVE HERE YEAR ROUND.

WHAT I'M GONNA DO NOW IS WE'RE GONNA GO DOWN IN ELEVATION.

I'M GONNA EXPECT THAT WE'RE GONNA MAYBE SEE SOME MORE PLANTS, MAYBE LESS SNOW, PROBABLY SOME MORE BIRDS, MAYBE EVEN SOME DIFFERENT SPECIES, AS WELL.

SO I'LL SEE YOU GUYS IN A COUPLE THOUSAND FEET.

, I'M GONNA KEEP BIKING DOWN, AND WE'RE GONNA SEE WHAT WE CAN SEE.

>> Chang: AND THAT IS IMOGENE CANCELLARE.

SHE IS AN ADVENTURER, A SCIENTIST, A BIOLOGIST, AND IN THIS INSTANCE A BICYCLIST.

AND IN ONE DAY, SHE'S GONNA EXPERIENCE THE CHANGE, FAST-FORWARDING THROUGH SPRING ON THAT ONE BIKE RIDE.

BUT I WANT TO TAKE A MINUTE NOW TO LOOK AT FOOTAGE THAT WE HAVE FROM CORNELL LAB OF ORNITHOLOGY.

MI IT'S A BIRD CAM.

AND JUST BEFORE WE CAME ON THE AIR, WE MANAGED TO WATCH THIS LITTLE CHICK BEING BORN.

>> IT'S JUST INCREDIBLE.

THERE, THERE COMES THE CHICK.

YOU CAN SEE HIM COMING RIGHT OUT OF THAT SHELL.

TWO MORE IN THE NEST THERE.

CO THIS IS FROM A RED-TAILED HAWK.

IT'S REALLY AN EXTRAORDINARY SIGHT.

>> Chang: AND WHAT'S INCREDIBLE IS THAT YOU CAN WATCH LIVE BIRD CAMS AND TAKE PART IN WHAT WE ARE CALLING "CITIZEN SCIENCE," RIGHT, AND WATCH THE BEHAVIOR.

LOOK IT.

OH, HERE IT COMES OUT OF THE EGG.

AND I'VE LEARNED THAT NOT-- ONCE ENTIST THEY'RE CALLED HATCHLINGS, WHEN THEY GET READY TO LEAVE THE NEST, THEY'RE CALLED EGG.

FLEDGLINGS.

I'M LEARNING THINGS EVERY DAY.

E AND WE'LL COME BACK AND TAKE A LOOK AT THEIR PROGRESS LATER ON IN THE BROADCAST.

>> THAT'S RIGHT.

>> Chang: THE MAMA, THE MAMA BIRD'S GONNA BE BACK ANY MINUTE, I'M SURE.

>> MM-MM, MM-MM.

>> Chang: AND AROUND US HERE IN THE SIERRA NEVADAS, YOU CAN SEE THAT THE SNOW MELT IS DEFINITELY KICKING IN.

BACK THERE IS A SNOW-CAPPED MOUNTAIN THAT IS MELTING RAPIDLY AND ADDING WA-WATER TO THE RIVER RUNNING BENEATH US HERE, AND FILLING UP THE KAWEAH RESERVOIR JUST A FEW MILES DOWNSTREAM.

AND A COUPLE WEEKS AGO, GUESS WHAT?

WE SET UP TIME-LAPSE FI CAMERAS OVER THERE.

LOOK WHAT'S BEEN HAPPENING.

S >> IT'S REALLY AN INCREDIBLE S BEEN HAPPENING.

SHOT.

JUST WATCH THE COLORS CHANGE AS THE PLANTS GREEN UP AND THEN BLOSSOM.

AND THIS IS HAPPENING NOT ONLY FROM THE INCREASE IN SUNLIGHT, BUT ALSO FROM THAT OTHER KEY SPRING INGREDIENT, WATER, WHICH IS ESSENTIAL FOR PLANT GROWTH AND FOR ALL OF THE THINGS THAT DEPEND UPON THOSE PLANTS.

ES SO THERE REALLY IS A BIOLOGICAL REASON, JUJU, WHY PEOPLE SAY L THAT APRIL SHOWERS BRING MAY FLOWERS.

REASON, JUJU, WHY PEOPLE SAY >> Chang: ABSOLUTELY.

WATER IS VERY MUCH THE STARTING B GUN IN MANY WAYS FOR SPRING.

AND I COULD WATCH THAT TIME-LAPSE PHOTOGRAPHY ALL DAY.

AND ALL OF THAT WATER THAT'S ADDED INTO THE SYSTEM, IT CREATES NEW PLANTS AND CHUTES THAT EMERGE, AND OBVIOUSLY, THE ANIMALS COME OUT AND TAKE TO ADVANTAGE OF THEM, INCLUDING THOSE COMING OUT OF HIBERNATION.

LET'S GO NOW TO THE ALLEGHENY MOUNTAINS IN MARYLAND.

LOOK AT THAT GLORIOUS SUNSET.

THAT'S WHERE WILDLIFE BIOLOGISTS ARE TRACKING A FAMILY OF BLACK BEARS AS PART OF A LONG-TERM STUDY OF THE HEALTH OF THEIR POPULATION.

JOINING US NOW IS DR. RAE WYNN-GRANT.

SHE IS A LARGE CARNIVORE ECOLOGIST.

BEARS ARE LARGE.

DR. RAE, I UNDERSTAND YOU'RE ON THE TRAIL OF A MOTHER BEAR RIGHT NOW.

>> THAT'S RIGHT.

HT I'M HERE IN THE FOREST WITH A TEAM OF BIOLOGISTS, AND AS YOU >> THAT'S RIGHT.

I AM HERE IN THE FOREST WI CAN PROBABLY SEE, IT'S DUSK HERE, WHICH, LUCKILY, IS ONE OF THE TIMES OF DAY THAT BLACK BEARS ARE MOST ACTIVE.

SO WE'RE REALLY HOPING IT MEANS WE'RE ABLE TO FIND SOMETHING.

I'M USING TELEMETRY EQUIPMENT TO MEANS HELP ME TRACK A BEAR RIGHT NOW.

THIS IS AN ANTENNA AND A RADIO DEVICE WHICH HAS A FREQUENCY BETWEEN THE COLLAR THAT THE BEAR IS WEARING WITH A DEVICE ON IT.

AS I GET CLOSER AND CLOSER TO THE ANIMAL, IT WILL EMIT A BEEPING SOUND, AND ONCE I'M ALMOST UPON THE ANIMAL, IT WILL BE VERY, VERY LOUD.

TODAY, I'M TRACKING A FEMALE BEAR THAT GAVE BIRTH THIS WINTER TO TWO CUBS.

R THAT GAVE BI AND I'M REALLY HOPING WE'RE ABLE TO FIND THEM, BECAUSE WE WANT TO CHECK ON THEIR HEALTH AND I'M REALLY HOPI WELL-BEING.

I'M HOPING THAT WE SEE THE CUBS AND THE MOTHER, BIGGER, STRONGER, AND FATTER THAN THE LAST TIME WE FOUND THEM.

THAT MEANS THAT THEY'RE HEALTHY.

THAT MEANS THAT THEY'RE STRONG.

IT ALSO TELLS US THAT THE ECOSYSTEM IS PROVIDING ENOUGH HAT THEY RESOURCES TO SUPPORT THEM THIS SPRING.

BIOLOGISTS ALL OVER AMERICA USE DEVICES JUST LIKE THIS TO TRACK BLACK BEARS.

A SOMETIMES TO FIND INDIVIDUALS, LIKE I'M DOING, BUT OTHER TIMES JUST TO MONITOR THE BEHAVIORAL PATTERNS AND MOVEMENTS OF OF ENTIRE POPULATIONS.

A COUPLE WEEKS AGO, I WAS FORTUNATE ENOUGH TO GO INTO THE DEN OF A HIBERNATING FEMALE BEAR.

AS CHECK IT OUT.

OKAY, HERE HE'S COME TO TRANQUILIZE THE MOTHER BEAR IN THE DEN.

>> THAT'S A GOOD SIGN, WHEN THEY'RE SCREAMING LIKE, THAT THEY WANT HER TO WAKE UP.

"MOM, WAKE UP."

>> SO THE CUBS ARE BEHIND THE MOTHER.

SHE'S TRANQUILIZED, BUT THE CUBS ARE MAKING A LOT OF NOISE RIGHT BEHIND HER.

THEY WANT MOM TO WAKE UP SO THAT THEY CAN KEEP NURSING.

SO WE'LL MAKE SURE THAT WE WRAP UP THIS WORK REALLY QUICKLY SO THAT THEY CAN BE ALL BACK TOGETHER.

HERE, BABY.

HI, BABY.

HI.

HI.

HEY.

HI.

HI.

WELCOME TO THE...

THEY HAVE NEVER BEEN EXPOSED TO THE OUTDOORS BEFORE.

THEY WERE BORN IN THEIR DEN ABOUT EIGHT OR TEN WEEKS AGO AND THEY'VE NEVER LEFT.

SO BEAR CUBS AT THIS AGE CAN'T THEIR D THERMOREGULATE, WHICH MEANS THAT THEY'RE NOT ABLE TO CREATE THEIR OWN BODY HEAT.

AND SO THEY NEED A MOTHER BEAR OR A BIOLOGIST LIKE ME TO MAKE SURE THEY STAY WARM WHILE THEY'RE OUT OF THE DEN.

OKAY.

SO WE HAVE NOTICED THAT WE HAVE A BOY, A BEAUTIFUL LITTLE BOY.

>> YEP, A MALE.

WE'LL TUCK HIM INTO A LITTLE BAG.

WE'LL SEX THEM, WEIGH THEM, MEASURE THEM, GET THEM TAGGED SO THAT WHEN WE FIND THEM AGAIN IN THE SUMMER, WE KNOW WHO THE INDIVIDUALS ARE.

AND WE CAN SEE THAT HE'S ABOUT SIX... >> SIX-AND-A-HALF IS WHAT I'M GONNA CALL THAT MALE.

IF I COULD HAVE YOU HOLD THE MALE JUST LIKE THAT, WE'RE GONNA MARK THIS BEAR WITH A PIT TAG, WHICH IS LIKE A OLD THAT T MICROCHIP THAT YOU WOULD PUT IN YOUR PET DOG, ONLY A DIFFERENT FREQUENCY.

>> A PIT TAG IS A GREAT WAY TO IDENTIFY THE BEAR IF WE COME ACROSS IT AGAIN.

EAR TAGS CAN SOMETIMES COME OFF T AS THE BEAR LIVES ITS LIFE CLIMBING TREES AND WHATNOT, BUT A PIT TAG STAYS IN PRETTY MUCH FOREVER.

SO WHEN WE FIND THESE PRECIOUS G LITTLE CUBS AGAIN IN THE SUMMER, WE WANT TO MAKE SURE THAT THIS R. FEMALE STILL HAS TWO CUBS.

IF SHE DOES, THAT MEANS THE ECOSYSTEM IS HEALTHY, THAT MEANS SHE'S HEALTHY, AND THAT MEANS THERE'S ENOUGH FOOD SOURCES HERE IN THIS FOREST FOR THEM.

THAT MEANS THERE'S ENO >> THIS IS JUST LIKE GETTING YOUR EARS PIERCED, SO ANYONE WHO'S EXPERIENCED THAT KNOWS THAT IT'S QUICK AND EARS ARE PRETTY PAINLESS.

>> AND THEY'LL HEAL FAST.

>> THESE EAR TAGS LOOK PRETTY LARGE RIGHT NOW, BUT THAT'S JUST BECAUSE OF THE SMALL SIZE OF THE CUBS.

ALL DONE.

ALL WE HAVE TO DO NOW IS CONTINUE KEEPING HIM WARM UNTIL WE PUT HIM BACK IN THE DEN WITH MOM.

IS >> ALL RIGHT.

CHRIS, CAN YOU GRAB HER COLLAR THERE?

IN ONE, TWO, THREE.

LET'S SEE A GOOD BREATH ON HER.

>> SO, A TEAM OF BIOLOGISTS HELPS TO PROCESS THE FEMALE.

A WE HAVE A VETERINARIAN WHO MAKES SURE THAT ALL OF HER VITAL SIGNS ARE LOOKING GOOD.

SO HER HEART RATE, HER BREATHING RATE.

IT TELLS US ABOUT THE STATE OF THIS BEAR IN PARTICULAR, BUT ALSO THE ECOSYSTEM AND THE HEALTH OF THE ECOSYSTEM.

>> 187 MINUS 25 FOR THE BASKET.

>> 162.

>> 162.

>> MOTHER BEAR IS HEALTHY, STRONG, VERY BIG, WHICH IS A GREAT SIGN.

THESE GUYS ARE JUST ANXIOUS TO START NURSING AGAIN.

WHICH THEY CAN DO BEFORE SHE WAKES BACK UP.

SO, WE'RE JUST ABOUT DONE.

MOM AND BABIES ARE BACK IN BA TOGETHER IN THE DEN.

IT WAS A HUGE EFFORT TO PUT THE MOTHER BEAR BACK IN, AS YOU CAN IMAGINE.

SHE'S HEAVY, SHE'S SEDATED.

THE BABIES WERE EASY.

THEY'RE IMMEDIATELY GOING TO START NURSING ON HER.

THE MOTHER WILL WAKE BACK UP IN THE NEXT HOUR OR SO.

SHE'LL BE GROGGY, BUT ESSENTIALLY SHE'S GONNA STAY IN HER STATE OF HIBERNATION.

THAT'S THE REALLY COOL THING T ESSENTIALLY SHE'S ABOUT DOING THIS DEN WORK, IS THAT THE BEARS NEVER LEAVE THAT HIBERNATION STATE UNTIL THEY'RE G OFFICIALLY READY ONCE THE WEATHER CHANGES.

>> Chang: IT'S EXTRAORDINARY, THE RESEARCH THAT THEY'RE DOING.

BUT LOOK, THERE'S THE MOTHER BEAR.

WE CAUGHT UP WITH THAT FAMILY JUST A COUPLE DAYS AGO.

AND LOOK AT THE BABY BEAR SCRAMBLING UP THE TREE.

>> LOOK AT THAT.

LOOK AT HIM CLIMB.

TH AND WHEN YOU SEE CUBS LIKE THAT, THERE'S A LOT OF INFORMATION THERE.

THOSE ARE PROBABLY EIGHT TO TEN-POUND BEAR CUBS, WHICH IS REALLY A HEALTHY SIZE FOR A THREE-MONTH-OLD CUB.

>> Chang: AND WE SHOULD EMPHASIZE THAT RAE AND HER TEAM ARE WILDLIFE PROFESSIONALS, AND THEY CLEARLY TAKE THE WELFARE OF THE BEARS VERY SERIOUSLY.

IT'S THEIR TOP PRIORITY.

>> IT IS.

IT IS.

AND THEY LEARN QUITE A LOT FROM THAT KIND OF RESEARCH IN THAT SEEING HEALTHY CUBS THIS TIME OF YEAR TELLS THEM SOMETHING ABOUT LAST SEASON, TOO, BECAUSE IF THAT MOTHER BEAR HAD NOT GOTTEN ENOUGH TO EAT OVER THE COURSE OF THE SPRING, SUMMER AND FALL, HER EMBRYOS WOULD NOT HAVE IMPLANTED INTO THE WALL OF THE UTERUS.

AND THAT IS A PROCESS THAT IS COMMON IN BEARS, AND IT IS ONE THAT IS CALLED DELAYED IMPLANTATION BY SCIENTISTS.

>> Chang: AND THERE GOES THE MAMA RIGHT NOW, CLIMBING UP THE LAYED IMPL BEAR, CHASING AFTER HER CLEARLY STRESSED-OUT LITTLE ONE.

BUT WHAT-WHAT... HOW DO THEY KNOW WHEN IT'S TIME FOR THE BEARS TO EMERGE FROM THE DEN?

>> WELL, THAT'S A REALLY GOOD QUESTION.

E FOR THE BEARS TO EMERGE FR AND IT'S ANOTHER GREAT EXAMPLE OF TIMING AND THE IMPORTANCE OF TIMING.

THEY'RE BORN IN THE DEN, BUT TH THEY DON'T EMERGE UNTIL SPRINGTIME WHEN THE GRASSES AND THE SEDGES AND THE INSECTS AND ALL THE OTHER THINGS THAT THEY NEED TO EAT ARE ABUNDANT.

>> Chang: I'D LOVE TO BRING DR. RAE IN ON THIS CONVERSATION AS WE'RE WATCHING THE MAMA BEAR AND THE BABY BEARS THAT WE TRACKED.

DR. RAE, WHEN YOU TRACK A FAMILY LIKE THIS, DO YOU GROW ATTACHED TO THEM?

>> OH, JUJU, I CAN'T HELP IT AT ALL.

EVERY SINGLE TIME I'M ABLE TO SEE THESE NEW ANIMALS BORN IN THE DEN AND THEN FIND THEM A LITTLE BIT LATER THRIVING, IT JUST MELTS MY HEART.

I ALWAYS GET ATTACHED.

I REALLY WANT TO FIND THIS ANIMAL AGAIN, AND SO I'M GONNA KEEP LOOKING.

>> Chang: AND WITH YOUR TELEMETRY, YOU'RE OUT ON THE PROWL.

WE CAN SEE IT.

THANK YOU SO MUCH, DR. RAE.

AND THANK YOUR TEAM FOR US, AS WELL.

YOU KNOW, THOR, ONE OF THE REASONS WHY THE BLACK BEARS ARE THRIVING ON THE EAST COAST IS THAT FORESTS OUT THERE ARE THRIVING TO A DECLINE IN LOGGING.

BUT HERE IN CALIFORNIA, THE FORESTS ARE UNDER A DIFFERENT KIND OF THREAT.

AND PHIL HAS BEEN EXPLORING THE GIANT SEQUOIAS OVER AT SEQUOIA NATIONAL PARK, AND HE HAS MORE.

PHIL.

NIA, THE FORESTS ARE >> HEY, YOU GUYS.

DO I HAVE SOMETHING TO SHOW YOU.

OKAY, TAKE A LOOK AT THIS.

THIS IS ALL BLACK HERE FROM NATIONAL PARK.

GO AHEAD, PHIL.

>> DO I HAVE SOMETHING TO SHO FOREST FIRES, BUT YET THIS TREE IS PROBABLY 1,500 YEARS OLD, ES, BUT YE MEANING IT'S SEEN A LOT OF FOREST FIRES.

AND IF YOU LOOK UP, YOU'LL SEE IT'S NOT JUST SURVIVING, IT IS THRIVING OUT HERE.

S NOW, NOT ALL TREES SHARE THAT SAME FATE WHEN IT COMES TO THE FOREST FIRES.

YOU CAN SEE THIS ONE HERE DIDN'T DO SO WELL.

IT CLEARLY GOT BURNED UP.

THIS ONE, THIS PINE, YOU'RE DOING ALL RIGHT, AREN'T YOU?

NOW, I WANT YOU TO TAKE A LOOK AT THIS MAP OF THE WESTERN N UNITED STATES.

LAST YEAR WAS ABSOLUTELY DEVASTATING FOR SO MANY COMMUNITIES AND SO MANY AREAS WHEN THESE FOREST FIRES GOT WAY OUT OF HAND IN A RECORD-BREAKING ANY AREAS YEAR.

NOW, CLIMATE SCIENTISTS BELIEVE OF THAT WITH CLIMATE CHANGE, FIRES LIKE THIS ARE ONLY GONNA GET WORSE.

SO WE HAVE TO BE CAREFUL WITH THIS, BUT THE IRONY IS SOME FORESTS ACTUALLY NEED A CERTAIN LEVEL OF FIRE.

THIS ONE INCLUDED.

NOW, TAKE A LOOK AT THIS BABY PRECIOUS LITTLE GIANT SEQUOIA.

IT CLEARLY HAS SOME GROWING TO DO, BUT IT'S GETTING THERE.

NOW, ONE OF THE ONLY WAYS THIS WING TO DO, BUT IT'S GETTING TH CAN HAPPEN IS WITH FOREST FIRE.

AND I'LL SHOW YOU WHY.

TAKE A LOOK AT THESE TWO PINE CONES.

THESE TWO CONES, I SHOULD SAY.

ONE OF THESE IS A SEQUOIA, AND THE OTHER ISN'T.

CAN YOU GUESS WHICH?

WELL, IT'S NOT THE BIG ONE.

IT IS THIS LITTLE ONE HERE.

H AND ONE OF THE FEW WAYS THAT IT IS THIS LITTLE ONE HERE.

THIS THING CAN ACTUALLY OPEN UP IS THE SEARING HEAT OF A FOREST FIRE.

ESSENTIALLY, THIS FOREST NEEDS FIRE TO COME THROUGH TO RELEASE THE RIGHT AMOUNT OF SEEDS.

AND YOU CAN SEE WHY.

I MEAN, LOOK AROUND HERE.

WITHOUT FIRE, THIS AREA WOULD PROBABLY GET A LITTLE BIT TOO OK DENSE, AND A LITTLE GUY LIKE THIS WOULDN'T HAVE ENOUGH ROOM TO GROW.

G AND LET'S BE HONEST, THEY GET BIG.

THEY NEED SOME ROOM TO GROW.

EY >> Chang: PHIL, THAT'S EXTRAORDINARY.

AND SPEAKING OF BIRTH AND REBIRTH, LET'S GO BACK NOW TO MEADOWCROFT FARM IN MAINE LIVE.

YOU CAN SEE THE NEWBORN LAMBS ALL HUDDLED ABOUT.

AND THEY'RE BEING VERY LOUD.

THEY'RE NOT JUST CRYING OUT FOR MILK, ARE THEY?

>> NO, IT IS NOISY IN THERE FOR A REASON, JUJU.

THAT SOUND IS... SOUND, AND YOU CAN HEAR IT THERE.

LISTEN TO THEM BLEATING.

ALL THE LAMBS, YOU CAN HEAR THE MOTHERS ANSWERING.

AND SOUND IS AN IMPORTANT WAY FOR THESE CREATURES TO BOND, TO FORM THAT EWE AND LAMB BOND, WHICH WILL BE VERY IMPORTANT WHEN THEY GO BACK OUT INTO THE FIELD.

WITH ALL THE OTHER ANIMALS OUT THERE, THEY NEED TO BE ABLE CH WILL BE TO FIND ONE ANOTHER, AND LISTENING TO EACH OTHER'S VOICES IS AN IMPORTANT WAY FOR THEM TO DO IT.

>> Chang: LET'S LISTEN FOR A SECOND.

[BLEATING] EARLIER, WE SAW ONE OF THE BABIES NURSING, AND THAT NEW BABY NEEDS A NAME.

SO, WHAT DO YOU THINK?

YOU SHOULD CHECK OUT OUR PBS NATURE FACEBOOK PAGE.

SEND US YOUR BEST, MOST CREATIVE IDEAS FOR A NAME.

AND WE'LL GET BACK TO YOU WITH THE BEST.

MEANWHILE, FARMS AND THAT KIND OF CONTROLLED ENVIRONMENT IS ONE THING, BUT OUT IN THE WILD, SPRING'S NEWBORNS HAVE TO DEAL WITH PREDATORS, AND THAT CAN BE A RELATIONSHIP THAT GETS VERY COMPLICATED.

SO FOR MORE ON THAT DYNAMIC, LET'S GO TO FLORIDA'S EVERGLADES.

THAT'S WHERE EMMY-AWARD WINNING WILDLIFE CINEMATOGRAPHER MARK EMERY IS OUT ON AN AIRBOAT.

LOOK AT THAT SCENERY.

MARK, HOW ARE YOU THIS EVENING?

FE >> HEY, WE'RE DOING GREAT OUT HERE, JUJU.

THIS IS AN AMAZING PLACE.

AND WE JUST HAD A WONDERFUL SUNSET JUST A FEW MINUTES AGO.

AND I JUST PANNED OFF A NEST.

I HOPE YOU SAW THAT.

WE'VE GOT A LITTLE FURRY WHITE BALLS BACK THERE.

AND THESE GUYS HAVE JUST FUN LITTLE WHITE ONESIES ON TONIGHT.

AND THEY'RE JUST SLEEPING RIGHT THERE BACK IN THE TREES, IF YOU CAN SEE THEM.

I'LL ZOOM IN A LITTLE BIT AND SEE IF WE CAN PICK THAT UP FOR YOU.

AND THEY ARE JUST NAPPING RIGHT NOW.

I DON'T BLAME THEM.

THEY'VE HAD A BIG DAY.

WE ACTUALLY HAD A NEST CAM GOING EARLIER TODAY, AND YOU COULD SEE HOW THEY WERE MOVING ALL AROUND.

THEY GOT CABIN FEVER IN THE NEST AFTER A WHILE.

AND THEY CAME OUT AND SAT ON THIS LIMB.

AND THIS IS A TENUOUS SITUATION AT BEST.

AND THEY CAME OUT AND SAT ON THESE LITTLE GUYS ARE JUST BARELY ABLE TO HOLD ON TO THESE LITTLE TINY TWIGS.

THEY CAN'T FLY YET.

SO THEY'RE IN A REAL TENDER SPOT HERE.

AND WE'RE HAVING TO REALLY STAY BACK AWAY FROM THEM.

AL TENDER SPOT HERE ON WE'VE GOT LONG LENSES ON.

AND WE'RE NOT BOTHERING THEM AT ALL.

IN FACT, THEY'RE STILL JUST NAPPING AWAY.

SES ON.

THEY'RE NOT STAYING AWAKE AT ALL.

BUT WHAT'S GOING ON HERE IN THE SWAMP IS JUST UNIQUE.

AND THE EVERGLADES IS THE PERFECT PLACE TO SEE IT.

THAT'S WHEN YOU HAVE A WHOLE ROOKERY OF BIRDS LIKE THIS NESTING AT ONE TIME OF THE YEAR.

AND THAT'S WHAT'S GOING ON RIGHT NOW.

ALL THE LITTLE GUYS ARE ALL UP IN THESE TREES.

THESE ARE CALLED ANHINGAS, AND ANHINGAS ARE A VERY PRIMITIVE BIRD.

THEY'RE REALLY COOL.

THEY'RE FOUND THROUGHOUT FLORIDA.

IN THE TREES.

BUT THEY ALSO NEST RIGHT AROUND THE SAME TIME AS A LOT OF THE OTHER BIRDS.

WE HAVE HERONS, EGRETS, IBIS, LOTS OF DIFFERENT SPECIES NESTING RIGHT NOW.

BUT THERE'S AN UNUSUAL ELEMENT GOING ON HERE.

YOU WONDER, HOW CAN A BIRD THIS FRAGILE AND THIS TENDER BE UP IN A TREE?

YOU KIND OF WORRY ABOUT SOME OF THE GREAT PREDATORS IN THE EVERGLADES.

YOU HAVE PANTHERS.

YOU HAVE, IN THIS CASE, GOING UP THE TREE WOULD BE PYTHONS.

YO THE BURMESE PYTHONS GET 15 FEET.

YOU HAVE ALL KINDS OF SPECIES UP IN THESE TREES, AND YOU ALSO HAVE COONS AND POSSUMS AND ALL THOSE KINDS OF CRITTERS.

SO HOW IN THE WORLD CAN THE PARENTS FLY OFF IN THE EVENING AND GO FISH AND COME BACK AND GET FOOD BACK AND FORTH WITHOUT JUST HAVING THAT HOME ALONE SCENARIO FEELING THAT SOMETHING BAD IS GONNA GO WRONG WHILE THEY'RE GONE?

WELL, THERE'S A PREDATOR THAT ALL THESE ANIMALS KNOW VERY, VERY WELL, THE ALLIGATOR.

THE AMERICAN ALLIGATOR IS ALL THROUGH HERE.

LAST NIGHT, WE DROVE THROUGH HERE.

W I DON'T KNOW HOW MANY WE COUNTED.

THAT PARTICULAR SPECIES RIGHT NOW IS KIND OF SHIFTING.

INSTEAD OF GOING AFTER A BIRD IN A NEST THAT HE CAN'T TAKE, HE'S ACTUALLY GOING AFTER THE PREDATORS THAT ARE TRYING TO TAKE THE BIRDS IN THE NEST.

SO WE SAW NO RACCOONS, NO TAKE THE BIRDS IN POSSUMS, NO PYTHONS LAST NIGHT.

WE JUST SAW A LOT OF ALLIGATORS.

AND SO IF YOU'RE GONNA BUILD YOUR NEST IN ONE OF THE TOUGHEST SWAMPS IN THE WORLD IN A REALLY BAD NEIGHBORHOOD AND YOU GOT THUGS IN THE BACKYARD AND UNDERNEATH YOU, PUT IT IN THE EVERGLADES IN THESE TREES.

BA IT'S A PERFECT PLACE FOR THESE GUYS TO TAKE ADVANTAGE OF THIS SITUATION.

SO YOU LITERALLY HAVE THIS STRANGE DICHOTOMY GOING ON WHERE ALLIGATORS ARE PROTECTING BABY BIRDS.

AND IT'S JUST AN AMAZING PLACE.

THESE ARE CALLED FLEDGLINGS AT THIS STAGE.

SO, IT'S AN AMAZING SETUP.

AND HERE WE GO.

WE'VE GOT ALL KINDS OF BEAUTIFUL THINGS HERE IN THE EVENINGS.

COME BY THE EVERGLADES.

YOU GOT TO SEE THIS PLACE, JUJU.

IT'S AMAZING.

>> Chang: MARK, I APPRECIATE THE INVITATION, BUT THE ALLIGATORS, I DON'T KNOW.

LET'S STEER CLEAR OF THOSE.

YOU KNOW, WHERE I LIVE IN NEW YORK CITY, CENTRAL PARK IS ACTUALLY ONE OF THE BEST PLACES IN THE WORLD FOR BIRD WATCHING.

I STUMBLE INTO TOURISTS WITH BINOCULARS ALL THE TIME.

BUT IT'S ALMOST IMPOSSIBLE TO FIND THEIR NESTS.

AND THERE'S A GOOD REASON FOR THAT.

FOR MORE, LET'S HEAD NOW TO ARIZONA AND THE SANTA RITA MOUNTAINS JUST OUTSIDE TUCSON.

SEE?

THAT'S DR. HAROLD GREENEY.

HE'S AN EXPERT AT FINDING NESTS IN THE WILD.

FOR DAYS NOW HE'S BEEN HUNTING FOR HUMMINGBIRD NESTS.

>> I JUST HEARD SOMETHING.

THERE'S A DISTINCT SOUND WHEN A FEMALE LEAVES THE NEST.

JUST "BUZZ!"

IT'S SOMEWHERE VERY CLOSE HERE.

SO I THINK SOMEWHERE UP HERE.

ST.

IT'S SOMEWHERE VERY CLOSE HE LET'S GO LOOK UP HERE HERE TO START WITH.

YEP, AH, THERE IT IS.

WELL, SHE MUST HAVE BEEN SITTING ON IT.

RE WE'LL SEE WHAT IT HAS INSIDE IT.

TWO EGGS.

THIS IS PROBABLY THE NEST OF A BLACK-CHINNED HUMMINGBIRD HERE.

AND ALL OF THESE MATERIALS THAT YOU SEE HERE, THE LICHENS, THE BITS OF LEAVES, THE OAK CATKINS, ALL OF THESE ARE BOUND TOGETHER WITH SPIDER WEBS.

SO THE SPIDER WEBS ARE BASICALLY THE CEMENT OR THE GLUE THAT THEY'VE USED TO ATTACH THEIR NEST HERE.

THE OTHER INTERESTING THING ABOUT THIS PARTICULAR NEST IS THAT YOU CAN SEE ALL ALONG THE T BOTTOM HERE THIS DARKER PART.

THIS IS LAST YEAR'S OLD NEST.

IT'S ALSO KIND OF HARD AND P CRUSTY HERE.

AND THIS UPPER PART, THE PALE AREA, THESE ARE ALL NEW MATERIALS THAT HAVE BEEN ADDED THIS YEAR.

SO THAT TINY LITTLE BIRD TRAVELED HUNDREDS AND HUNDREDS OF MILES DOWN TO MEXICO AND THEN BACK HERE TO THE EXACT SAME BRANCH, NOT THE SAME CANYON, NOT THE SAME AREA, THE EXACT SAME BRANCH.

ONE OF THE THINGS I FOUND IS THAT IF I GET LOWER TO THE GROUND, EVEN LIE FLAT, THAT TENDS TO BE LESS THREATENING TO THE FEMALE.

AND IT MIGHT ENCOURAGE HER TO COME IN, SO I'M GOING TO LAY DOWN REALLY LOW, AND THEN I'LL SEE IF THAT WORKS.

OH, HERE SHE COMES.

IT'S JUST BEHIND THE NEST NOW PERCHED LOW.

LET'S HOLD REALLY STILL.

PERCHED LOW.

HOLD REALLY ST ALL RIGHT, SHE'S ON THE NEST.

THIS IS AMAZING.

WOW.

LOOK AT THAT.

SO BEAUTIFUL.

SHE'S JUST SPENT A COUPLE DAYS BUILDING THAT WHOLE STRUCTURE, LAYING THOSE EGGS.

SHE'S EVEN PUT CALCIUM FROM HER OWN BONES INTO THE EGGSHELLS.

SO SHE'S REALLY DEPLETED HER ENERGY AND... AND HER TIME TO INVEST IN THIS NESTING STEP.

SO SHE'S GOING TO BE VERY, VERY CAUTIOUS ABOUT REVEALING ITS LOCATION TO ANY PREDATORS WHO MIGHT BE WATCHING.

WHICH IS WHY SHE DOESN'T JUST FLY STRAIGHT BACK TO THE NEST.

YOU CAN SEE HER SORT OF WIGGLING.

WHAT SHE'S DOING, SHE'S DOING SEVERAL THINGS.

ONE, SHE'S SHAPING THE NEST, SO SHE'S USING HER BODY TO CREATE THE FORM OF THE NEST, STRETCHING THOSE SPIDER WEBS INTO THE POSITION THAT SHE NEEDS THE NEST TO BE IN.

THE OTHER THING IS SHE'S MAKING SURE THE BARE PATCH OF SKIN ON HER BELLY IS COMING INTO DIRECT CONTACT WITH THE EGGS.

THAT'S HOW SHE'S KEEPING THEM WARM, WITH USING HER OWN BODY HEAT.

SO OFTEN WHILE SHE'S INCUBATING, SHE'LL BRING BACK NEW MATERIAL TO ADD TO THE S OUTSIDE AS CAMOUFLAGE.

GLUE THAT ON THE OUTSIDE WITH THE SPIDER WEB.

AH, THIS IS SUCH AN INTIMATE LOOK AT HER LIFE AT THE NEST.

YEAH, YOU CAN SEE SHE'S JUST SETTLED IN THERE.

BUT HER HEAD IS NEVER STILL.

SHE'S LOOKING, LOOKING, ALWAYS VIGILANT.

ANY SORT OF SHADOW OR ANYTHING PASSES OVERHEAD, SHE'LL IMMEDIATELY SLIP OFF THE NEST.

>> Chang: I JUST LOVE THAT HAROLD IS FLAT ON HIS BELLY TO GET A BIRD'S-EYE VIEW OF THIS, BUT LOOK AT HOW SMALL THIS HUMMINGBIRD'S NEST IS.

WE'VE GOT ONE RIGHT IN FRONT OF US.

BUT THIS MIGHT BE A GOOD TIME TO MENTION THAT WE SHOULD REALLY NEVER PICK UP OR TOUCH NESTS, RIGHT, THOR?

>> YEAH, IT'S TRUE THAT NESTS AND BIRDS ARE PROTECTED BY UL THE MIGRATORY BIRD TREATY, SO IT'S REALLY ILLEGAL TO TAKE THESE THINGS FROM THE WILD.

>> Chang: WE HAVE TWO BEAUTIFUL SPECIMENS HERE, AND THEY'RE ACTUALLY MORE THAN A HUNDRED YEARS OLD, I UNDERSTAND.

'S ILLEGAL TO TAKE THESE FROM >> THEY ARE.

THESE ARE ON LOAN TO US FROM THE NATURAL HISTORY MUSEUM AT THE UNIVERSITY OF CALIFORNIA BERKELEY.

THEY WERE KIND ENOUGH TO LEND US A BEAUTIFUL HUMMINGBIRD NEST FROM AN ANNA'S HUMMINGBIRD, AND YOU CAN SEE, NOW THAT WE'RE THIS CLOSE, YOU CAN REALLY SEE HOW IT'S BUILT FROM THOSE SPIDER WEBS, AS WELL AS DECORATED WITH LICHENS TO KEEP IT CAMOUFLAGED.

JUST A WONDERFUL, WONDERFUL NEST.

>> Chang: IT LOOKS LIKE A WORK OF ART-- SO WELL CAMOUFLAGED.

AND THIS IS A ROBIN'S NEST.

A AND ARE THEIR EGGS REALLY BLUE?

>> THEIR EGGS ARE INDEED ROBIN'S KS LIKE A WORK EGG BLUE, AND THAT NEST IS ALSO DECORATED WITH LICHENS TO HELP IT BLEND IN, AND IT'S FUSED TOGETHER WITH MUD.

I MEAN, IT'S JUST A...

IT'S A WORK OF ENGINEERING AND IT TAKES GREAT SKILL.

>> Chang: IT TAKES A LOT OF EFFORT.

I CAN'T IMAGINE THAT A HUMAN CAN BUILD ONE.

>> IT'S IMPOSSIBLE.

I CHALLENGE YOU TO TRY IT.

EFFORT.

I CHALLENGE YOU TO TRY IT.

GET YOURSELF A PILE OF SPIDER WEBS AND A PAIR OF TWEEZERS, AS A BEAK, AND YOU TRY THE MAKE A NEST OUT OF THAT.

TRY TO MAKE ANYTHING, AND IF YOU TRY THAT EXPERIMENT, O YOU WILL BE VERY IMPRESSED WITH THE SKILL LEVEL OF BIRDS >> Chang: WELL, I'M ALREADY IMPRESSED BY THEIR ARTISTRY.

THIS IS EXTRAORDINARY.

I MEAN, THESE...

THIS IS JUST A WORK OF ART.

IT'S BEAUTIFUL.

AND IF YOU'RE AS FASCINATED BY THESE BIRDS' NESTS AS WE K CERTAINLY ARE, THERE IS A WAY YOU CAN CONTRIBUTE TO SCIENCE WITHOUT EVEN HAVING TO LEAVE YOUR HOUSE.

PHIL TORRES HAS AN EXAMPLE.

PHIL?

>> HEY, GUYS.

SO CITIZEN SCIENCE IS SCIENCE THAT YOU CAN DO RIGHT FROM YOUR HOME AND SOMETIMES LITERALLY RIGHT ON YOUR COUCH, AS YOU'RE ABOUT TO FIND OUT IN ONE OF MY FAVORITE PROJECTS OUT THERE-- IT'S CALLED BIRD CAM LABS.

AND JUST WAIT UNTIL YOU SEE THIS FOOTAGE.

IT'S INCREDIBLE.

TAKE A LOOK.

>> MY NAMED IS DAVID COHEN, I AM AN ARTIST, A NATURE LOVER, AND TODAY I AM A CITIZEN SCIENTIST.

I KNOW I CERTAINLY WATCHED BIRDS FOR YEARS JUST LOOKING OUT AND SEEING THEM FLY OR LAND ON A BRANCH, BUT WHAT WAS ACTUALLY HAPPENING IN THAT NEST I HAD NO IDEA ABOUT.

L THE BIRD CAMS PROVIDE A WINDOW INTO NATURE THAT HAS NEVER BEEN THERE BEFORE.

NOW, WE'LL START OUT, WHAT WE'RE GONNA TRY AND DO IS STICK IT UP JUST A LITTLE BIT BELOW WHERE THE CURRENT CAMERA IS.

CORNELL LAB OF ORNITHOLOGY HAD BIRD CAMS RUNNING FOR OVER 20 YEARS AT THIS POINT.

BIRD CAMS LAB IS KIND OF A UNIQUE APPROACH TO TRYING TO ANSWER THE QUESTIONS OF SCIENCE.

COOL.

THAT'S IT.

AS CITIZEN SCIENTISTS, WE WANTED TO KNOW, DO HAWKS USE DIFFERENT CALLS TO MEAN DIFFERENT THINGS?

DO THE VOCALIZATIONS HAVE DIFFERENT MEANINGS?

BY HAVING PEOPLE WATCH AND RESPOND BY SAYING WHAT THEY HEARD AND WHAT THEY SAW IN THE CLIPS WHEN THESE CALLS WERE ON BEING DONE, THAT'S A GREAT OPPORTUNITY, AND IT IS SOMETHING THAT IS NOT READILY AVAILABLE IN THE SCIENTIFIC INFORMATION TODAY.

>> ONE THING WE'VE HEARD FROM CAM VIEWERS SINCE DAY ONE IS HOW FUN, INTERESTING, ENTERTAINING, AND FULL OF DISCOVERY WATCHING CAMERAS ARE.

YOU'RE SITTING IN FRONT OF A COMPUTER, FOR GOODNESS' SAKE, AND YOU'RE WATCHING THE LIFE OF A BIRD OR A FAMILY OF BIRDS THAT ARE PROVIDING INCREDIBLE AMOUNTS OF INFORMATION AND JOY.

>> IT'S JUST CRAZY.

IT'S JUST...

IT'S JUST REALLY CRAZY.

>> NOW, I KNOW SOMEWHERE AT THE TOP OF ONE OF THESE TREES THERE HAS GOT TO BE A BIRD NEST UP THERE SOMEWHERE.

BUT LET'S BE REAL, THAT'S... THAT'S PRETTY HIGH UP.

I DON'T THINK I CAN CLIMB UP THERE.

SO I'M VERY THANKFUL FOR PROJECTS LIKE BIRD CAM LABS I THAT ALLOWS US TO PEEK INTO THAT SECRET INCREDIBLE LIFE OF BIRDS AND THEIR NEST AND DO SOME SCIENCE AT THE SAME TIME.

HOW GREAT IS THAT?

NOW, IF YOU WANT TO FIND OUT OME SCIENCE AT THE SA MORE ABOUT THIS, CHECK OUT OUR PBS NATURE FACEBOOK PAGE.

WE HAVE A WHOLE MENU OF CITIZEN SCIENCE PROJECTS ON THERE.

AND WHILE YOU'RE ON IT, PLEASE LEAVE SOME COMMENTS.

LEAVE SOME QUESTIONS.

AND AT THE END OF THE HOUR, WE'RE GONNA BE ANSWERING SOME OF THOSE QUESTIONS LIVE ON AIR.

IT'S GOING TO BE GREAT.

E BACK TO YOU, GUYS.

>> Chang: THANKS TO PHIL.

AND, YOU KNOW, IT'S THRILLING WATCHING THIS LITTLE CHICK KS BECOME A HATCHLING.

W, IT'S TH WE WATCHED IT HAPPEN BEFORE OUR VERY EYES.

AND THIS IS THE BIRD CAM THAT IS THE RED-TAILED HAWK.

AND HERE'S WHAT IT LOOKS LIKE NOW.

>> WATCH THAT ACTION.

I MEAN, THIS IS THE TYPE OF THING THAT CITIZEN SCIENCE CAN DO.

YOU KNOW, THERE...

THERE IS A LOT OF DATA TO BE GATHERED IN THE WORLD, AND THERE AREN'T THAT MANY SCIENTISTS, SO HAVING THESE CAMERAS WHERE PEOPLE CAN WATCH FROM HOME JUST EXPANDS THE QUESTIONS THAT WE CAN ASK.

>> Chang: AND THIS IS NOT BLACK AND WHITE.

THIS IS NOW DARKNESS ON THE EAST COAST LIVE.

THIS IS THE, UH, BIRD CAM IN ITHACA AT CORNELL.

>> THAT'S RIGHT.

>> Chang: AND WE SEE THE MAMA N HAWK HAS COME BACK TO WARM HER CHICKS, AND THEY'RE CALLED HATCHLINGS, AS WE'VE LEARNED.

AND TWO MORE COULD HATCH AT ANY SECOND AT THIS POINT >> AT ANY TIME.

AND YOU CAN SEE THE WAY SHE'S RELAXED IN THAT NEST.

SECOND AT THIS POINT SHE'S COVERING AND PROTECTING THOSE EGGS, AND SHE HAS HER BILL TUCKED UNDER HER WING AND IS HAVING A NICE REST.

>> Chang: AND IF YOU'RE INTERESTED IN LEARNING MORE CK ABOUT CITIZEN SCIENCE PROJECTS LIKE PHIL WAS TALKING ABOUT, YOU SHOULD CHECK OUT SCISTARTER ON OUR AMERICAN SPRING WEBSITE.

IT'S SCI LIKE S-C-I, SCIENCE, RIGHT?

AND WE CAN CHECK OUT THE WEBSITE AT PBS.ORG.

AND NOW WE CAN CHECK IN WITH OUR WILDLIFE BIOLOGIST AND CYCLIST, IMOGENE CANCELLARE, SHE'S HALFWAY DOWN, I THINK.

REMEMBER SHE LAUNCHED HERSELF DOWN THE MOUNTAIN?

>> DOWN THE MOUNTAIN, YES.

>> Chang: AND SHE WANTED TO EXPERIENCE WHAT SPRING'S ARRIVAL WAS LIKE IN ONE BIKE RIDE.

LET'S TAKE A LOOK A GRAPHIC.

THOUGH, THOR, SO YOU CAN EXPLAIN HOW THAT BIKE RIDE UNFOLDS AND WHAT SHE'S SEEING.

>> SURE.

SO, WHAT SHE'S REALLY EXPERIENCING IS THE SIMILARITY BETWEEN ALTITUDE AND LATITUDE.

SHE IS FINDING SPRING ALONG THE WAY AS SHE DESCENDS FROM SNOW AND ICE ALL THE WAY DOWN TO THAT VALLEY BOTTOM.

SHE'S GOING, LIKE, FROM A POLAR REGION THOUSANDS OF MILES SOUTH TO SOMEPLACE WARM, AND SHE'S ENCOUNTERING SPRING ALONG THE WAY.

LET'S SEE HOW FAR SHE'S GOTTEN.

>> WELL, WE'RE HALFWAY DOWN OUR JOURNEY HERE ON THE MOUNTAIN.

AS YOU CAN TELL, EVERYTHING LOOKS TOTALLY DIFFERENT.

THERE IS NO LONGER SNOW SURROUNDING ME, AND CONSEQUENTLY THE ECOSYSTEM'S A LITTLE BIT DIFFERENT AS WELL.

SINCE WE'RE HALFWAY DOWN, WE'RE JUST OVER 4,900 FEET IN ELEVATION, AND THE TEMPERATURE HAS CHANGED SI SIGNIFICANTLY.

JUST OVER 4,90 IT'S A LOT WARMER.

I HAD TO LOSE A LAYER.

AND HERE I'M SEEING SIGNIFICANTLY MORE SIGNS OF THE EMERGENCE OF LAYER, AND HERE SPRING.

I'M SEEING DIFFERENCES IN THE VEGETATION COMMUNITY.

NOT ONLY ARE THERE LESS PINE TREES, BUT WE'RE ALSO SEEING TONS OF BEAUTIFUL WILDFLOWERS THAT ARE JUST SMATTERING THE LANDSCAPE.

IN THIS MORE DESERT ARID NS ECOREGION, SPRING IS REALLY IN FULL SWING.

SO WHAT I'M GONNA DO NOW IS THE SAME THING THAT I DID FARTHER UP, IS I WANT TO TEST THE SOIL TEMPERATURE.

BUT I AM GONNA BE CAREFUL NOT TO RTHER UP, DESTROY THIS LITTLE MICROCLIMATE FOR ALL OF THESE BEAUTIFUL WILDFLOWERS THAT WE SEE HERE.

THE TEMPERATURE OF THE SOIL IS 94 DEGREES FAHRENHEIT.

THAT'S REALLY, REALLY WARM.

BUT WE CAN SEE THAT THESE FLOWERS ARE FLOURISHING IN THIS ENVIRONMENT.

ADDITIONALLY, WE'RE GONNA SEE A WHOLE LOT OF OTHER DIFFERENT ANIMALS ON THIS LANDSCAPE.

JUST BEHIND ME, I SAW SOME SCAT FROM DEER.

AND JUST OVER THERE, ON MY WAY DOWN, I SAW SOME FOX SCAT.

SO LOTS OF ANIMALS ARE USING THIS LANDSCAPE, DESPITE THE FACT THAT IT IS HOTTER AND A LITTLE BIT DRIER.

IT IS HOTTER AND A LITTLE BIT SO THIS JOURNEY'S NOT OVER.

I'M GONNA HOP ON MY BIKE AND CONTINUE MY WAY DOWN.

SO I'LL SEE YOU THERE.

>> Chang: I LOVE THAT IMOGENE IS HAVING A GLORIOUS BIKE RIDE AND MAKING SCIENTIFIC OBSERVATIONS ALONG THE WAY.

BUT IF YOU'RE JUST JOINING US, THIS IS "AMERICAN SPRING LIVE," AND I'M JUJU CHANG.

THIS IS MY NEW FRIEND, DR. THOR HANSON, AND WE'VE BEEN TALKING ABOUT ALL SORTS OF BIRTH AND REBIRTH THAT HAPPENS.

>> THAT'S RIGHT.

WE'VE BEEN TALKING ABOUT HOW THERE'S A RELATIONSHIP BETWEEN THE TIMING OF REPRODUCTION AND THE TIMING OF FOOD AVAILABILITY IN NATURE.

THAT'S BEEN A BIG FEATURE FOR US, BUT IT'S ALSO SOMETHING THAT CLIMATE CHANGE IS AFFECTING.

RE BECAUSE AS THE CLIMATE WARMS, SPRING IS HAPPENING SOONER AND SOONER IN MANY AREAS.

AND THAT RELATIONSHIP IS STARTING TO UNRAVEL FOR SOME SPECIES, BECAUSE NOT ALL SPECIES REACT TO THAT CHANGE IN THE SAME WAY.

>> Chang: AND... >> SO THAT'S SOMETHING THAT SCIENTISTS ARE-ARE VERY CONCERNED ABOUT.

>> Chang: BECAUSE IT CLEARLY HAS A CASCADING EFFECT.

THAT'S FASCINATING.

NOW LET'S CHECK BACK IN WITH THOSE WADING BIRDS ALL THE WAY OUT IN THE FLORIDA EVERGLADES.

N I THINK THERE ARE SOME GATORS, TOO, PERHAPS?

CHECK OUT THAT SUNSET.

IT'S GLORIOUS.

WE HAVE WILDLIFE CINEMATOGRAPHER MARK EMERY STANDING BY.

SO WHAT ARE YOU SEEING OUT THERE?

>> ONE MINUTE, 30.

>> IF YOU LOOK NOW, I THINK YOU CAN SEE THROUGH MY LENS, I'M RIGHT ON AN ALLIGATOR'S EYE.

E AND HE'S JUST POKING THROUGH THE GRASS JUST A LITTLE TINY BIT.

THIS IS A PERFECT LIE-IN-THE-WAIT PREDATOR.

HE DOES NOT MOVE.

HE'LL SIT THERE FOR HOURS UNTIL SOMETHING COMES BY, AND HE SIMPLY EXPLODES ON 'EM.

IT IS SO FAST.

AND THEIR EYE IS AN E-ESSENTIAL TOOL FOR WHAT HE'S DOING.

THIS PARTICULAR GUY HAS AN EYE LIKE A ELLIPTICAL, LIKE A CAT.

AND AT NIGHT, LIKE THIS, IT OPENS UP, AND IT IS ENTIRELY BLACK.

IF YOU'RE OUT HERE SHINING YOUR LIGHT, YOU'LL SEE AN ORANGE GLARE, AND YOU KNOW THAT'S A BIG ALLIGATOR LOOKING BACK AT YOU.

IF HIS EYES ARE THE SIZE OF QUARTERS, HE'S PRETTY GOOD.

IF THEY'RE THE SIZE OF A HALF-DOLLAR, OH, MY.

SO, WE'RE RIGHT ON ONE RIGHT NOW.

AND THESE ARE THE PROTECTORS OF THOSE BIRDS WE WERE JUST LOOKING AT EARLIER.

ALLIGATORS ARE UNUSUAL IN THAT, THIS TIME OF YEAR, THEY'RE ALSO DOING THEIR MATING.

A LITTLE BIT LATER THAN THE BIRDS.

SO IT'S IMPORTANT FOR THEM TO GET A-A GOOD MEAL NOW AND THEN, TOO.

SO HE'S OUT HERE HUNTING AT NIGHT.

AND-AND EARLY AND LATE IN THE DAY, THEY'LL BE BELLOWING.

IT'LL CRANK UP.

IT'LL SOUND LIKE AN OLD HARLEY-DAVIDSON.

LIKE THAT.

AND WATER WILL FLY OFF HIS CHIN AND OFF HIS BACK.

SO THE MATING SEASON IS COMING, AND IT'S RIGHT AROUND THE CORNER.

SO SPRINGTIME IS BIG-TIME HERE IN EVERGLADES NATIONAL PARK.

WE'VE STILL GOT HIM RIGHT THERE.

>> YOU GUYS, WE ARE SO LUCKY RIGHT NOW, BECAUSE WE ARE SEEING SPRING IN ACTION.

TAKE A LOOK BEHIND ME.

WE HAVE MULE DEER UP HERE THAT ARE FEEDING.

THIS IS SO INCREDIBLE TO WATCH.

NOW, JUST A FEW WEEKS AGO, THIS ENTIRE AREA WAS COVERED IN SNOW.

AGO, THIS BUT NOW THAT SPRING IS HERE, ALL OF A SUDDEN, ALL THESE NEW SHOOTS OF GREEN ARE COMING UP, IS AND THE DEER HAVE MIGRATED UP THE MOUNTAIN TO TAKE ADVANTAGE SE NEW CHUTES OF GREEN ARE COMING UP AND THE DEER HAVE MIG OF THAT NEW RESOURCE.

AND IT'S NOT JUST THE DEER.

IN FACT, ACTUALLY, ON OUR DRIVE UP HERE TODAY, WE SAW A MAMA BEAR AND HER TWO CUBS.

I MEAN, THIS IS THE BEST TIME OF YEAR TO BE OUT HERE.

SEQUOIA NATIONAL PARK AND SPRINGTIME-- THIS IS THE PERFECT MIX.

BACK TO YOU GUYS.

, >> Chang: THANKS, PHIL.

WE'RE SO GLAD YOU TOOK A DETOUR AROUND MAMA BEAR.

AND, YOU KNOW, IT'S GETTING TO BE BEDTIME NOW ON THE EAST COAST FOR OUR NEWBORN LAMBS.

LET'S HEAD BACK TO MEADOWCROFT T FARM IN MAINE.

YOU CAN SEE THE BARN.

THAT'S WHERE ALL THOSE BABY LAMBS ARE.

THEY'VE BEEN BLEATING AWAY, TRYING TO BOND NOW, WE'VE LEARNED, WITH THEIR MOTHERS.

ATING AWAY, SO, THOR, WHEN DO THEY ACTUALLY STOP NURSING AND START GRAZING?

>> WELL, IT CAN BE ABOUT A MONTH BEFORE THEY SWITCH FROM THAT MILK DIET TO A DIET OF GRASS.

UH, AND THAT IS A-ANOTHER EXAMPLE OF HOW IMPORTANT TIMING IS.

BUT THIS IS ONE WHERE FARMERS HAVE THE ABILITY TO SORT OF GAME THE SYSTEM.

THEY CAN SCHEDULE THIS SEASONAL EVENT, WHAT-WHAT A-A SCIENTIST WOULD CALL AN-AN ACT OF PHENOLOGY, THE STUDY OF SEASONAL EVENTS IN NATURE.

THEY CAN GAME THAT SYSTEM BY SCHEDULING THE TIME OF BREEDING IN THE FALL SO THAT THINGS HAPPEN AT THE RIGHT TIME IN NA SPRING FOR THEIR PARTICULAR FARM.

>> Chang: AND, CLEARLY, TIMING IS EVERYTHING WHEN IT COMES TO SPRINGTIME.

ALL EVENING LONG, WE'VE BEEN WATCHING AS OUR CYCLIST-SCIENTIST IMOGENE CANCELLARE HAS BEEN FAST-FORWARDING HER WAY ON A R BIKE RIDE DOWN THE SIERRA NEVADA MOUNTAINS.

LET'S SEE WHERE SHE IS NOW.

>> WELL, I MADE IT.

WE'RE AT THE END OF MY BIKE JOURNEY HERE TODAY.

WE STARTED AT THE TOP OF THE MOUNTAIN, AT JUST UNDER 8,400 FEET, AND WE HAVE MOVED ALL THE WAY DOWN.

AND ALL OF THIS GRASS THAT'S GREEN IS GREEN AND RICH AND HEALTHY BECAUSE THERE IS SO MUCH MOISTURE DOWN HERE IN THE VALLEY FLOOR.

THE TREES THAT ARE BEHIND ME HERE INDICATE THAT I'M RIGHT BY HERE ON THE VALLEY FLOOR.

A RIPARIAN CORRIDOR, WHICH MEANS THAT THERE IS A BODY OF WATER FLOWING THROUGH HERE.

SO I'M GONNA HIKE BACK HERE INTO THIS SLIGHTLY MORE SHADED AREA AND CHECK OUT BOTH THE SOIL TEMPERATURE AND LOOK FOR SOME MORE SIGNS OF WILDLIFE THAT I E SAW AND HEARD ON MY WAY IN.

SO LET'S SEE.

CHECKING OUT THE SOIL TEMPERATURE.

I'M LOOKING AT ABOUT 74 DEGREES FAHRENHEIT.

THE TEMPERATURE IS GOING TO BE LOWER THAN IT WAS AT THE MIDSLOPE DUE TO THE FACT THERE IS MORE WATER IN THIS AREA, WHICH IS REALLY GREAT, BECAUSE IT MEANS THAT THE GRASS IS PROVIDING INSULATIVE ABILITY FOR E THE SOIL, SO IT RETAINS WATER, WHICH IS GOING TO MAKE THE PLANT LIFE, THE BULBS, THE GRASSES HEALTHY AS THEY CONTINUE TO GROW.

AND AS A RESULT, WILDLIFE IS BENEFITING FROM IT.

ALL BEHIND ME, LISTEN... A RESULT, WILDLIFE IS I CAN HEAR SO MANY DIFFERENT BIRDS THAT I WASN'T HEARING EARLIER TODAY.

LOTS OF DIFFERENT SPECIES-- GRASSLAND SPECIES, FOREST BIRDS-- ARE TAKING ADVANTAGE OF THIS LANDSCAPE BEHIND ME.

THE WATER IS GONNA BE PROVIDING RESOURCES FOR A VARIETY OF WILDLIFE, INCLUDING BOBCATS OR NG TO BE COYOTES OR RABBITS AND DEER.

AND, YES, IF SOME OF THE BEARS OR THE MOUNTAIN LIONS DECIDED TO MOVE DOWN HERE, THEY COULD TAKE ADVANTAGE OF THESE RESOURCES AS WELL.

IT'S BEEN A REALLY, REALLY GREAT BIKE JOURNEY TODAY.

I'VE HAD A LOT OF FUN.

AND I HOPE YOU ENJOYED GETTING OUTSIDE AND SEEING SPRING YOURSELF.

G >> Chang: WELL, THANKS SO MUCH.

THANKS TO IMOGENE.

SHE'S SO ATHLETIC.

WE'RE GRATEFUL FOR THAT.

AND ONLINE, AS PHIL HAS TOLD YOU, WE'VE BEEN ASKING YOU TO SEND US YOUR QUESTIONS AND COMMENTS TO OUR FACEBOOK PAGE.

SO, RIGHT NOW, WE'RE GONNA PUT THOR TO THE TEST AND ASK HIM SOME OF THOSE QUESTIONS THAT'S BEEN COMING IN.

SO LET'S CHECK IT OUT.

SARAH MADE A COMMENT.

SHE SAID, "WHY DO MOST ANIMALS GIVE BIRTH IN THE SPRINGTIME?"

>> OH, IT'S A GREAT QUESTION.

AND AS WE'VE BEEN TALKING ABOUT, THERE'S A REAL RELATIONSHIP BETWEEN THE AVAILABILITY OF FOOD G IN SPRINGTIME, WHEN ALL THAT ENERGY PUMPS UP THE SYSTEM, AND TIMING OF BIRTH.

SO REPRODUCTION TENDS TO HAPPEN IN SPRING, WHEN FOOD IS AVAILABLE.

>> Chang: AND GINA ASKS THAT SHE S LOVES THE IDEA OF THE BIRD CAMS AND CAN'T WAIT TO SIGN UP.

BUT M-MIA ASKS, "WHERE CAN WE LEARN MORE ABOUT BIRDS IN OUR E IDEA OF THE BIRD CAMS AREA?"

>> YOU KNOW, THE BEST WAY, REALLY, I THINK, TO LEARN ABOUT BIRDS IN YOUR LOCAL AREA IS TO GO OUT INTO THE FIELD WITH SOME IN YO BIRDERS.

LEARN FROM THE PEOPLE WHO ALREADY KNOW, AND THEY CAN HELP YOU NOT ONLY TO IDENTIFY WHAT YOU SEE, BUT THEY KNOW WHAT TO EXPECT.

>> Chang: AND, CLEARLY, THAT KIND OF ENTHUSIASM IS INFECTIOUS.

ELIZABETH WANTS TO KNOW, HOW MANY BEARS LIVE IN NORTH AMERICA?

>> AH, THE BEARS OF NORTH AMERICA.

WELL, WE'VE BEEN TALKING A LOT ABOUT THE BLACK BEAR, WHICH IS THE MOST COMMON BEAR IN NORTH AMERICA.

, THERE ARE MORE THAN HALF A MILLION OF THEM.

AND WE ALSO HAVE BROWN BEARS OR T GRIZZLIES IN NORTH AMERICA, AND THEY'RE A LITTLE MORE SCARCE AND LIVE MOSTLY UP IN CANADA AND ALASKA.

AND THE RAREST BEAR THAT WE HAVE ON THIS CONTINENT IS OUR POLAR BEAR, WHICH LIVES IN THE ARCTIC REGIONS AND WHICH IS SUFFERING NOW FROM HABITAT LOSS DUE TO CLIMATE CHANGE.

>> Chang: THOR, I LOVE HAVING ALL OF YOUR INSIGHTS WITHIN CONTINENT IS THE ARM'S LENGTH OF ME.

WE WANT TO THANK YOU ALL FOR JOINING US HERE ON "AMERICAN SPRING LIVE," ON THIS AMAZING NIGHT OF BIRTH AND REBIRTH.

AND, TOMORROW NIGHT, WE'LL BE BACK, AS A TEAM, LIVE AT 8:00, WITH A LOOK AT THE SCIENCE BEHIND MIGRATION, WHICH IS LIVE."

TOMORROW NIGHT WE'LL BE SPRING'S GREATEST TRAVELING SHOW-- HOW ANIMALS GET FROM POINT "A" TO POINT "B" AND, MORE IMPORTANTLY, WHY.

>> MM-HMM.

>> Chang: AND FOR THE FIRST TIME EVER, WE'LL HAVE CAMERAS LIVE INSIDE THE LARGEST BAT CAVE-- CHECK IT OUT, IT'S THE LARGEST ONE ON EARTH-- CAPTURING THE MOMENT THAT THEY SWARM OUT INTO THE NIGHT SKY.

IT'S NEVER BEEN DONE BEFORE.

WE'LL GIVE IT A SHOT.

PHIL?

>> I'M GONNA BE HEADING OUT OF THE PARK AND INTO THE MEADOWS PHIL?

BELOW THAT ARE ABSOLUTELY FULL OF WILDFLOWERS RIGHT NOW.

AND I'M GONNA BE USING THIS TO TRACK DOWN MIGRATORY BUTTERFLIES.

>> Chang: THANKS, PHIL.

FROM ALL OF US... >> WE WANT YOU TO PARTICIPATE IN THIS BROADCAST.

SO HEAD TO THE PBS NATURE FACEBOOK PAGE TO ASK US QUESTIONS, SHARE SPRING STORIES, AND POST YOUR PHOTOS AND VIDEO.

YOU CAN ALSO VISIT NATURE'S WEBSITE TO LEARN HOW TO BECOME A CITIZEN SCIENTIST, PLAY A PART, AND MAKE A DIFFERENCE IN THE PURSUIT OF CRITICAL DATA ABOUT SPRING.

>> THIS IS HOW WE GET THE BIG PICTURE OF WHAT'S HAPPENING IN OUR WORLD.

Captioning sponsored by WNET Captioned by Media Access Group at WGBH access.wgbh.org Captioning sponsored by WNET Captioned by Media Access Group at WGBH access.wgbh.org