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The Making Of A Bird's Egg
April 20, 2015

Yolanda's recovery (bounce back) is slow this time around.

Still, we give thanks.

I have a doctor's appointment today for what I think is a nasty sinus infection, and that doesn't help matters.

In typical man fashion, I waited too long.

Hopefully I can get some good meds to knock this out.

I also turned another year older last week.

For one week, we were blessed with some true spring like weather.

We even managed to hit the mid 70's fahrenheit on Friday and Saturday.

Bird activity is at a frenzied pace.

Almost every week a different species makes an appearance.

Daffodils and other fall bulbs are blooming.

I even saw my first butterfly of the year, early last week.

It's not a great picture, but clearly shows to be a Question Mark basking in the early week sunshine.

This coming weeks is forecast to be much below normal.......


Another one of Creation's wonders is that of the bird egg.

The complexity, and beauty that goes into making an egg is yet another one of His miracles.

It also give you another look at the or inside our feathered friends.


No way.


Oology: This is the branch of ornithology that deals with the anatomy and physiology of eggs as well as the size, shape, color and other characteristics.

You know feel a tad bit smarter today.

Don't you?

Back to the task at hand.

After mating, inside the female, sperm may wait several weeks or swim up a tube called the oviduct, at the end of which there is an ovum.

If the ovum is mature, it's already equipped with yolk, the yellow part of the future egg.

The sperm may now fertilize the ovum by penetrating it and uniting the two reproductive-cells' genetic material.

Fertilization doesn't necessarily take place soon after mating; domestic chickens and turkeys can produce fertile eggs seventy days after copulation.

After fertilization, the ovum with its yolk begins its own journey down the oviduct, a process lasting about 24 hours.

During the first three or four hours, moving along the way, the albumen (egg white) is added around the ovum and its yolk.

(The picture is a bird ovary and you can see the different stages of the yolk and ovum as it develops.)

The yolk will serve as food material for the developing chick; the white will mainly keep the yolk from drying out, and will give the yolk physical support.

A Sidebar:

(The yolk size varies from bird to bird. The more independent the hatchling is, the larger the yolk will be.

Geese, ducks and chickens have a larger yoke per egg size than birds hatched helpless.)

Now,the future egg slows to about 40 percent of its earlier speed, and membranes are added around the yolk and egg white.

Finally the shell is put in place, taking 19 to 20 hours

The egg then moves to the uterus, or shell gland, where the calcareous shell is added and, in some birds, pigment is added in characteristic patterns.

The shell is mostly composed of the mineral called 'calcium carbonate', which has the same chemical formula as limestone.

(No wonder egg shells are so hard and brittle.)

Pretty amazing that all of this is built up around the yolk in a 24 hour period.

The egg then passes into the vagina and cloaca for laying.

I would call that one efficient assembly line.

Wouldn't you?

Technically speaking, eggs are single cells, even though we normally think of cells as too small to see with our naked eyes.

In fact, eggs are the largest cells known in the animal kingdom.

They range in size from tiny ones produced by hummingbirds (0.006 oz, or 0.2 gram), to nearly 20 LBs (9 kg), laid by the Elephant Bird of Madagascar, which is now extinct, but was known by primitive humans.

The Components Of An Egg:

An egg has four basic structures: the yolk and its associated membranes, the germinal disc,the albumen (white), and the shell and its associated membranes.

Each component performs specific functions in the development of the embryo.

The yolk is the main source of nutrition for the embryo.

The fat gives yolk its yellow color. The more fat contained in the yolk, the darker the yellow.

Surrounding the yolk are four membranes that keep it intact and in contact with, but separate from, the albumen.

After the egg has been fertilized and incubation starts, a system of blood vessels develops within these yolk membranes, which completely surround the yolk and carry nutrition to the embryo.

On the surface of the yolk is the germinal disc, a small disc of cytoplasm containing the DNA nucleus of the female cell, or ova.

You need a microscope to see the nucleus, but you can see the germinal disc with the naked eye.

It appears on the surface of the yolk as a white dot.

“If the egg is fertile, the dot is called a blastoderm; if it is not fertile, it is called a blastodisc.” The blastoderm contains the genetic material necessary to develop into offspring of the parent birds.

The albumen is the white or clear part of the egg that surrounds the yolk.

Made up mostly of protein, it also contains globulins, which provide immunity from disease.

The albumen feeds the developing embryo with water and protein. When the chick is ready to hatch, the albumen acts as a lubricant to help the chick turn, push and struggle to free itself from the egg.

Albumen consists of thick viscous forms and thin, watery forms.

A layer of watery albumen surrounds the yolk, and a more viscous layer of albumen is in contact with the watery layer.

A third watery layer of albumen is in contact with the shell’s inner membrane.

A dense layer of albumen called the chalaziferous layer is in direct contact with the outer yolk membrane.

An extension of this layer forms the chalazae, twisted strands of thick albumen that connect to the shell membrane at each end of the egg.

The chalazae (pronounced 'Kel-aze... with a long A) stabilizes the yolk and embryo in the center of the egg within the albumen layers.

The chalazae is much like a shock absorber that keeps the yolk and embryo stable.

The chalazae become twisted as the egg is turned during incubation (much like a rubberband).

(These nearly invisible strands are what make it difficult to separate the white from the yolk when recipes call for whites or yolks.)

The hard outer surface of a bird egg is the shell.

It provides protection and structure to house the embryo.

The shell contains pores to allow for transpiration of water through the shell.

The shell consists of three layers; the outermost layer is the cuticle.

Beneath the cuticle is the calcium carbonate layer called the testa, and the innermost layer is the mammillary layer.

The cuticle consists of dried mucus laid down by the uterus and serves to regulate evaporation of moisture and to protect the embryo from bacterial infection.

The testa is the layer that makes up most of the eggshell structure and provides calcium to the growing chick.

It is also the layer that contains the pigments if the egg is colored.

The mammillary layer is in direct contact with the shell membranes and is the foundation for the testa.

Two membranes lie directly beneath the shell: the inner shell membrane and the outer shell membrane

At the blunt end of the egg, the two membranes separate, forming a space between them called the air cell.

The air cell is formed after the egg is laid and cools.

The outer shell membrane adheres to the mammillary layer of the shell. The inner shell membrane covers the liquid inside the egg.”

"Nature" has made it possible for birds to lay from a single egg to 20 or more and have them sit dormant for a period of time until incubation begins.

This way all the eggs can hatch within hours of each other.

Some birds do lay and hatch on an every other day schedule, however.

Next week incubation and more.

Well, it's time to fly for now.

Before I go, here is your positive thought for the week.

God Bless.

"Worry and fear cannot live in the same space with hope and action. When you stand on faith and take positive action, you evict worry and fear."

Dondi Scumaci

The Word of God gives us this gem.

"Peace I leave with you; my peace I give you. I do not give to you as the world gives. Do not let your hearts be troubled and do
not be afraid." John 14:27

"Treat the earth well:

It was not given to you by your parents,

It was loaned to you by your children.

We do not inherit the Earth from our

Ancestors, we borrow it from our Children."

Ancient Indian Proverb

Your friend indeed,

Ron Patterson

PS. If you enjoy these letters, please forward them to friends, family and co-workers.

Better yet, have them sign up so they can receive their own letters.

Gardening For Wildlife.

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