0:00:02 > 0:00:05MUSIC: "Spring" by Vivaldi
0:03:48 > 0:03:52MUSIC: "Summer" by Vivaldi
0:07:46 > 0:07:50MUSIC: "Autumn" by Vivaldi
0:11:40 > 0:11:43MUSIC: "Winter" by Vivaldi
0:18:23 > 0:18:26We all love autumn, don't we?
0:18:26 > 0:18:28It's the time we celebrate horrible Halloween
0:18:28 > 0:18:31and fantastic Fireworks Night!
0:18:34 > 0:18:37But autumn means winter is on the way.
0:18:37 > 0:18:39And whilst we are having fun,
0:18:39 > 0:18:42trees have to get ready for the coming cold snap.
0:18:44 > 0:18:50Leaves trap sunlight to make food, in a process called photosynthesis.
0:18:50 > 0:18:52But in the winter, there's not enough sun
0:18:52 > 0:18:54for them to work properly.
0:18:54 > 0:18:58The trees stop making the green chemical called chlorophyll
0:18:58 > 0:19:01that catches the sunlight,
0:19:01 > 0:19:05and the yellow, brown and red colours underneath begin to show.
0:19:22 > 0:19:25They look brilliant.
0:19:25 > 0:19:28And as they die and fall off, they are great fun to catch,
0:19:28 > 0:19:30kick through and enjoy.
0:19:33 > 0:19:37But what happens to them after they have landed on the ground?
0:19:37 > 0:19:40Almost 1.5 billion trees
0:19:40 > 0:19:44lose their leaves in our country every year.
0:19:44 > 0:19:48That's around 25 trees for every person living here.
0:19:49 > 0:19:52They drop thousands of tonnes of leaves on the ground.
0:19:52 > 0:19:57So how is it that we don't end up buried in leaves?
0:19:57 > 0:20:00It's one of nature's secrets.
0:20:02 > 0:20:06Every year, a slimy demolition squad springs into action.
0:20:12 > 0:20:16This is one of the key members of the squad, the earthworm!
0:20:20 > 0:20:24They love the moist leaves because they breathe
0:20:24 > 0:20:28through their skins, and their skins need to be wet to work.
0:20:28 > 0:20:32In the autumn, they wriggle up from the ground
0:20:32 > 0:20:34into the piles of damp autumn leaves...
0:20:36 > 0:20:40..to do lots and lots of eating.
0:20:41 > 0:20:45They munch their way through the leaves,
0:20:45 > 0:20:48breaking them up into smaller pieces.
0:20:48 > 0:20:51These then get mixed up with the soil,
0:20:51 > 0:20:54making the ground a better place for plants to grow.
0:20:59 > 0:21:01Our next demolition agent
0:21:01 > 0:21:03looks like something you might eat.
0:21:05 > 0:21:07Mushrooms.
0:21:12 > 0:21:15They can't make their own food from sunlight,
0:21:15 > 0:21:18so they live off things like rotting leaves.
0:21:18 > 0:21:23Mushrooms and toadstools spread tiny spores through the air,
0:21:23 > 0:21:26like seeds in the wind.
0:21:26 > 0:21:28But even if they look good to eat,
0:21:28 > 0:21:31you should never pick wild mushrooms.
0:21:33 > 0:21:37Some are so poisonous, they could kill even a grown-up.
0:21:46 > 0:21:47This is the third
0:21:47 > 0:21:51and slimiest member of our leaf demolition squad.
0:21:53 > 0:21:57This yellow moving goo is called a slime mould.
0:22:05 > 0:22:08One sort is called the scrambled egg slime mould,
0:22:08 > 0:22:12and another, the dog vomit!
0:22:13 > 0:22:17For most of the year, slime moulds are just tiny blobs,
0:22:17 > 0:22:19but in autumn, they gang together
0:22:19 > 0:22:22and creep around like a moving carpet.
0:22:24 > 0:22:27They haven't got eyes or a nose,
0:22:27 > 0:22:30but they are really good at finding food,
0:22:30 > 0:22:33like rotting leaves and other moulds.
0:22:37 > 0:22:40This yellow mould has found a white one to eat.
0:22:43 > 0:22:46It wouldn't be hard to get out of their way, though.
0:22:46 > 0:22:48We are watching them speeded up,
0:22:48 > 0:22:52but really, slime moulds can only move one millimetre an hour.
0:22:52 > 0:22:55So it would take them a whole day and a night
0:22:55 > 0:22:58to travel the length of your little finger.
0:23:03 > 0:23:07When the food runs out, they use the same trick as mushrooms.
0:23:07 > 0:23:11They send lots of tiny spores into the air
0:23:11 > 0:23:14to make new slime moulds in other damp places.
0:23:21 > 0:23:26So, if you take a trip out to see the autumn leaves this year,
0:23:26 > 0:23:30take a bit of extra time to look for the unsung heroes of the autumn.
0:23:32 > 0:23:34The slimy demolition squad!
0:23:43 > 0:23:45It's spring!
0:23:45 > 0:23:49Shoots are shooting up, flowers are bursting out,
0:23:49 > 0:23:50and baby animals
0:23:50 > 0:23:52are appearing everywhere.
0:23:53 > 0:23:55We love seeing them,
0:23:55 > 0:23:59but what does it really take to raise a baby animal?
0:24:02 > 0:24:06This little bluetit is ready to start a family of baby birds.
0:24:06 > 0:24:12He's found the perfect hole for a nest and now he's started singing.
0:24:13 > 0:24:16BIRDS SING
0:24:16 > 0:24:19In fact, all the birds are singing.
0:24:20 > 0:24:23They might look as though they're just enjoying
0:24:23 > 0:24:27the nice spring weather, but actually, they're hard at work.
0:24:31 > 0:24:36Singing is their way of finding a partner and telling the world
0:24:36 > 0:24:40they are going to build a nest and that no-one else is allowed here.
0:24:41 > 0:24:46But once they've got their patch sorted, their mission begins.
0:24:49 > 0:24:54These birds are called shags. They live on an island near Newcastle.
0:24:57 > 0:24:59They build nests out of sticks.
0:25:02 > 0:25:04Some collect their own.
0:25:06 > 0:25:09But others steal from birds nesting near them.
0:25:16 > 0:25:19Sometimes, from right under their beaks!
0:25:34 > 0:25:40Other birds make nests out of moss, straw, or even spider webs.
0:25:42 > 0:25:45Our little bluetit makes his nest out of feathers
0:25:45 > 0:25:47and dried-out plants,
0:25:47 > 0:25:50and then it's time for the eggs!
0:25:56 > 0:25:58Not chocolate eggs!
0:25:59 > 0:26:01Whilst we're having a feast,
0:26:01 > 0:26:04the birds are looking after the real eggs,
0:26:04 > 0:26:06which is a far more serious business.
0:26:09 > 0:26:11The birds heat the eggs up
0:26:11 > 0:26:13with the warmth from their tummies.
0:26:15 > 0:26:18If the eggs get cold, the chicks inside will die.
0:26:22 > 0:26:26For some birds, mum and dad take it in turns to do the egg-sitting.
0:26:28 > 0:26:31But sometimes, mums do all the hard work.
0:26:33 > 0:26:36Eider duck mums sit on their eggs
0:26:36 > 0:26:39without eating for four whole weeks.
0:26:39 > 0:26:42They must get very hungry.
0:26:49 > 0:26:52It's even harder when it starts to rain.
0:26:52 > 0:26:54The birds can get very cold and wet.
0:27:08 > 0:27:12Luckily, the bluetit mum laid her eggs
0:27:12 > 0:27:14in a nice, cosy tree hole.
0:27:15 > 0:27:17Look! The chicks have hatched.
0:27:20 > 0:27:23But the hard work is only just starting.
0:27:23 > 0:27:26Now they've got to get lots of food
0:27:26 > 0:27:28into all those hungry beaks.
0:27:29 > 0:27:32But these bluetits have done something really clever.
0:27:35 > 0:27:39Like lots of birds, they've timed their eggs to hatch
0:27:39 > 0:27:42just as the leaves start to come out on the trees.
0:27:47 > 0:27:50But, er, hang on a minute,
0:27:50 > 0:27:53baby bluetits don't eat leaves!
0:27:53 > 0:27:57Well, there's something else that does eat them.
0:27:58 > 0:28:02Caterpillars love munching on the tender new leaves.
0:28:06 > 0:28:09And there's something else that likes eating caterpillars.
0:28:12 > 0:28:14Baby bluetits!
0:28:18 > 0:28:22So, there are lots of caterpillars for the baby birds.
0:28:22 > 0:28:24Which is lucky, since each chick
0:28:24 > 0:28:27can eat 100 caterpillars every day!
0:28:30 > 0:28:34Now you know just how hard animal parents have to work
0:28:34 > 0:28:37to keep their babies happy and healthy.