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Where do baby chicks come from?
Those cute, fluffy baby birds recently hatched out of eggs! How did they live in their eggs? How long did it take for them to get out of the eggs? Keep reading to find out!
The Case of the Disappearing Eggshell
An egg is covered by a hard shell to help protect the chick growing inside. When the chick is ready to hatch, it breaks the shell open. Try this experiment to find out what a shell is made of:
Set a raw egg in a glass of white vinegar so that it's completely covered in the liquid. Bubbles should start to form on the surface of the egg.
Let the egg sit in the vinegar for about 3 days and then take it out and rinse it in water, being careful not to pop it. Does it feel different from when you put it in the vinegar? Does it still have a white shell?
The eggshell disappeared! But there might be some chalky white stuff left on the egg. This is because vinegar is a type of acid that "ate" away and dissolved the calcium carbonate that the shell is made out of. (Chalk is also made out of calcium carbonate!) When something dissolves, it breaks into very tiny pieces and mixes with a liquid. You can see it happening if you put a sugar cube into a cup of hot water and stir. The sugar cube disappears as the sugar dissolves into the water.
You might be wondering why the egg white and yolk inside the shell stayed in the shape of an egg even though the shell is gone. This is because the egg has another covering underneath the shell; called a membrane. It is very thin and you can see the yellow yolk through it. The vinegar can't dissolve the egg membrane, but some of it was able to get through the membrane, making the egg swell up.
In the last project, the egg membrane let liquid in, making the egg swell a little bit. Do this project to see if you can get the egg to shrink!
The egg shrank! This is because the egg membrane let a bunch of water pass out of the egg to try to balance how much water was inside the egg and how much water was outside it in the glass. The very tiny parts that make up corn syrup (called molecules) were still too big to pass through the membrane, so none of the corn syrup got inside the egg. The egg lost a lot of water, but didn't get anything to take the water's place, so it looks a little funny! Do you think it would fill up again if you put it in a glass of water? Try it out!
The fact that the egg membrane can let some things through is very important for a baby chick. Air passes through the membrane, just like water did in this experiment, and that allows the baby chick to breathe while it's inside the egg.
When baby chicks hatch, they are covered with tiny, soft, fluffy feathers called down. Down helps keep them warm. (It can keep us warm too, which is why quilts and coats are often stuffed with down!) As they grow older, chicks grow bigger feathers called contour feathers. These are colored on the tips and downy at the base (the part closest to the body) to help keep them warm. They also grow long, strong flight feathers on their wings and tail. Look at a feather up close to learn more about it:
A hen can lay between 100 and 300 eggs per year, but she can only lay one per day. Her eggs will only have chicks growing inside them if she has a rooster husband. If there is no rooster, the eggs are for eating!
Chickens don't have teeth. They swallow their food whole into a gizzard that has tiny stones in it to grind up the food before it goes to the stomach.
Did you hear the joke about the broken egg? (Answer: Yes, it cracked me up!)
What do chicks do in science class? (Answer: EGGsperiments!)
Who tells the best chicken jokes? (Answer: Comedi-HENS!)
Way Cool Websites
Watch this video to see a chick hatching from its shell! (Uses Quicktime.)
See pictures of how a chick develops while you take care of it in this online incubator.
How a Chick Hatches
A mother chicken is called a hen. The baby chick's life cycle starts when its mother hen lays an egg. This egg has a big yellow yolk that contains all the food the chick needs while it grows inside the egg. The yolk floats in the egg white, which protects it and contains water for the chick. For about 21 days the hen sits on her eggs and covers them with her feathers to keep them warm. Several times a day she turns the eggs with her beak. She does this to keep the yolk from sinking down and crushing the chick against the shell.
When it is time for the chick to hatch, it pecks holes in the shell with a bump on its beak called an egg tooth. A few days after the chick has hatched, the egg tooth falls off because the chick doesn't need it any more. The chick in the picture still has its egg tooth. The chick has to take lots of breaks to rest, and when it finally gets out of the shell it doesn't get up and move right away -- it's too tired! Its feathers are wet and stringy, but they soon dry and become fluffy.
Baby chicks grow up fast. Young girls are called pullets and young boys are called cockerels. Pretty soon they will be grown-up hens and roosters and start having their own babies!
All birds lay eggs, but they don't all do it in just the same way:
Eggs come in lots of different colors and sizes. A hummingbird egg is the size of a jelly bean. A robin egg is blue and about the size of a quarter. Ostrich eggs are the largest; they are bigger than a grapefruit!
There are lots of different names for baby birds! In general, they are called chicks or hatchlings, but some types of birds have special names. Here are a few:
Groups of hatchlings are sometimes called a brood or a clutch. Groups of grown-up birds can have different names, too. Usually they are a flock, but a group of geese is called a gaggle and a group of ducks is called a brace.
Print out this coloring sheet to help kids match the baby birds with their parents!
Down - tiny, soft, fluffy feathers that keep the chick warm.
Hen - a grown-up, mother (female) chicken.
Yolk - the yellow part of the inside of the egg. This gives the baby chick the food it needs to grow.
Egg Tooth - a bump on the chick's beak that it uses to crack the shell so it can hatch.