Lesson video

Hi, everyone.

My name is Miss Hummel, and I'm excited to be answering the question today: Why do birds lay eggs? Let's have a look.

In this lesson, we'll learn the lifecycle of a bird, particularly focusing on a chicken.

We will also look at the differences between a hatchling, a nestling and fledgling.

We'll discuss and label the anatomy of a chicken egg.

And finally, we will discuss strategies which birds use to attract mates.

The structure of our lesson will be as follows.

We will begin by looking at the lifecycle of a bird.

We will follow that by discussing the anatomy or the structure of a chicken egg.

Finally, we will learn about different strategies that birds use to attract their mates.

In this lesson, you will need an exercise book or paper, a pencil or a pen, a coloured pencil or pen, and a ruler.

If you haven't got those things, pause the video and go get them now.

Here are our star words, which are the most important words of our lesson.

I'm going to say them and ask you to repeat them after me.

When I point at myself, it will be my turn, and when I point at you, it will be your turn.

Life cycle.

Bird.

Chicken.

Egg.

Chick.

Hatchling.

That was a bit of a harder one.

Nestling.

Fledgling.

Now we should know the words: lifecycle, bird, egg, and chicken, but we may not know the words: chick, hatchling, nestling, and fledgling, which we will discuss in the lifecycle of a chicken.

We will start by looking at the lifecycle of a chicken, which is a type of bird.

Now, all birds begin their lives carefully enclosed in eggs.

The size and the colour of the eggs and the amount of time a bird remains inside the egg varies by species, but eventually all birds emerge from the egg.

I would like to clarify at this point that not every egg that is laid by a chicken would develop into an animal.

This is because not every egg that a chicken lays would have been fertilised by sexual reproduction.

The eggs that we eat and buy from the supermarket are eggs which have not been fertilised and would not develop into chickens.

When a chicken is developing inside of the egg, we call it an embryo.

Moving on, I find it really interesting that some birds possess a specialised temporary bony growth on their beaks called an egg tooth that helps them crack open the shell and hatch.

During the time immediately following, most young birds exit from an egg.

It's known as a hatchling.

However, this isn't the case for a chicken which emerges as a chick.

A chick is covered in soft down instead of feathers, and it cannot fly.

Birds that are fully feathered and can fly from their nest are considered adult birds.

Those birds are ready to find mates and build nests of their own so that they can lay eggs and become parents themselves, and then they start the bird lifecycle all over again.

Now, I want us to see if we can act out the lifecycle of a chicken.

First, we can start as an egg.

Can you think of an action for an egg? I might do this for my egg.

Then we become an embryo.

So an embryo, it's developing inside.

Eventually we will hatch.

Can you pretend that you're a chick that is hatching from an egg.

When we are chicks, we cannot fly and we have soft fur.

See if you can create some actions to help you remember that.

Finally, I grow feathers and can fly, and I'm now considered an adult chicken.

We're now going to look at the definitions of hatchling, nestling and fledgling.

These three words are often used for many types of birds which are not chickens.

So it's still important that we know them.

Now, we mentioned earlier that for most birds during the time that they immediately hatch from an egg, they're known as a hatchling.

Then young birds are covered in soft down instead of feathers, and they cannot fly.

This makes them vulnerable to predators and incapable of feeding themselves.

At this stage, baby birds are called nestlings because they spend all of their time snug in the nest, relying on their parents for protection and for food.

Eventually, nestlings lose their down and sprout feathers, which they need for flight.

Young birds who are growing flight feathers and learning to fly are called fledglings.

These young birds work hard to practise the skills required for flying and to strengthen their muscles.

Once their flight feathers have grown in, fledglings take their first flight, which is called a fledge.

Now, for all of those words: hatchling, nestling, and fledgling, we can find something in the word that's going to help us remember them.

In hatchling, we can find the word hatch; in nestling, we can find the word nest; and in fledgling, we can find the word fledge, which we said stands for the first flight.

So those things can help us remember those three words.

I would now like you to pause the video to complete your thinking task, which is, what is the difference between a hatchling, a nestling, and a fledgling? You can resume the video once you're finished.

We're now going to learn about a chicken's anatomy.

Anatomy refers to the science of identifying and describing the structure of living things.

Here is a fully labelled diagram of a chicken egg.

Do you recognise any parts of the egg already? You may have recognised the yolk and the shell of an egg.

Let's discuss each part of the egg in more detail.

The air chamber is an empty space located at the large end of the egg.

I can remember this because when I have peeled boiled eggs before, I've noticed that there's one end of the egg which seems to have some air.

Now, chamber is a fancy word for room.

So I can think of it as a little room for air.

Before we look at the yolk, point to the air chamber on your screen.

The yolk is the yellow inner part of the egg where the embryo will form.

The yolk contains the food that will nourish the embryo as it grows.

Some of my friends say that the egg yolk is their favourite part of the egg to eat.

Point at the yolk on the screen to prove that you know where it is.

Next, we're going to focus on the albumen.

Watch the pronunciation there because you may think it's albumen because of the word album, but it's actually albumen.

Now, the albumen is the egg white, and it contains proteins.

When albumen is raw, it's usually transparent, but when it's been cooked, it becomes white.

Now some of my friends who go to the gym a lot had egg white omelettes or albumen omelettes so that they have lots of protein to help them get strong.

Before we discuss the chalaza, have a go at pointing at the air chamber, now the yolk, and now the albumen.

The chalaza is a spiral rope-like strand that anchors.

Anchors means keeps in place the yolk in the thick egg white or the albumen.

There are two chalazae anchoring each yolk: one on the top and one on the bottom.

Can you think of an action that's going to help you remember the chalaza? Maybe you can think of it as a rope or as a spiral keeping the yolk in the right place.

The blastodisc is a small, circular white spot, which is about two to three millimetres across on the surface of the yolk.

That means on the outside of the yolk.

It's where the sperm, which is the male sex cell enters the egg.

Now, if an egg were to be fertilised, this is where the fertilisation would occur.

Now, I can remember this word because I can think of the fact that the verb blast usually means to break something.

So it's like it broke a hole in the yolk.

And a disc usually refers to a circular object, which helps you remember the fact that it's circular.

Now we should all know the next structure, which is the shell.

A shell is the hard, protective coating of the egg.

We don't want to eat the shell of an egg.

See if you can test your knowledge by pointing out the chalaza.

Remember, there's two of them.

And the blastodisc.

The final structure is the shell membrane, which is a thin membrane located just inside the shell.

Sometimes you can see the membrane when you're peeling a boiled egg.

When I've been peeling a boiled egg, sometimes I've noticed kind of a thin layer that gets stuck to the shell.

That's the shell membrane.

Now is your turn to label or sketch a diagram.

Try to label the diagram of a chicken egg.

If you don't have it in front of you, just sketch your own diagram that you can label.

Please pause the video to complete this task.

When you're finished, you can resume the video.

This is how you should have labelled your diagram of a chicken egg.

Make sure to check and correct your work with a different coloured pen or pencil.

For our final part of the lesson, we will discuss one of my favourite topics of this unit, which is how do birds attract their mates? We will first read a statement that will tell us one of the ways in which birds attract a mate.

Most male birds, such as robins or chaffinches are the brightest and most colourful at the start of spring.

They hope that their fresh new plumage will attract a female.

Can you think of any birds that you have seen which are bright or colourful? We've spoken about birds having colourful feathers, but some birds have taken things a step further by developing special feathers just for showing off.

Male pheasants have some spectacular feathers.

The tail feathers of the male argus pheasant, which is from Southeast Asia can reach 1.

75 metres in length, which is taller than me.

We can see a photo of a pheasant on the left-hand side of your slide.

On the right, we can see a peacock, which also has very colourful and attractive feathers.

Sometimes to impress a mate, birds may perform special displays.

Birds of paradise from Papua, New Guinea dangle from a branch, shaking their dazzling feathers.

Can you pretend like you're a bird of paradise shaking your dazzling feathers? Cranes make dancing leaps into the air, calling loudly and tossing up pieces of the earth.

I will leave it up to you to decide if you want to make some dancing leaps into the air.

Other birds display together in pairs to prepare for breeding.

It's almost like they dance together.

I loved watching that video.

Now, birds may also track their mates by showing off their skill and their hard work.

Raise your hand if you have ever shown off your skill or hard work.

I certainly have.

Now, male wrens, which are a type of bird build many different nests in the hope that a female will like one of them and move in.

Bowerbirds from Australia build an amazing house of grass called a Bower and even create a front garden, which the male bird sweeps clean with a twig and decorates with flowers and pebbles.

Who would have known that a bird could possibly do more chores than you? I really enjoyed that video.

Now for this task, I would like you to fill in the table, listing three examples of how male birds attract their mates.

Write a short description for each method with an example of a type of bird.

If you don't have a table in front of you, you will need to make sure that you use your ruler to draw a neat table like the one that you can see here.

Please pause your video now to complete your task.

You may resume once you have finished.

When you finish that last task, make sure to complete your exit quiz by exiting the video and clicking on the quiz.

This will test your knowledge and your understanding.

This is now the end of our lesson.

I hope you enjoyed it as much as I did.

Bye.