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Incubation Of the Egg
April 27, 2015

After snow this past week, and a record cold Friday morning, we are promised some spring like weather for this week.

Healing is slow around here, but we are making headway.

Yes, there appears to be an end to the rough season we have endured.

Thank You Lord.

Yolanda is slow to mend, but we see a gimmer.

Pictured below are a couple of robins as they enjoy hunting amongst the leaf litter in the flower beds.

To your right, is a female robin collecting nesting material.

If I haven't said this before, I will now.

With robins, the male selects the territory, the female selects the nest sight within his territory and she alone constructs the nest.

Last week I wrote on the making of a bird egg.

This week is a simple version on incubating and hatching of the egg.


(Duck and Rabbit enjoy a feed together.)

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 chalazae stabilizes the yolk and embryo in the center of the egg within the albumen layers.

The chalazae become twisted as the egg is turned during incubation.

This is that invisible band or shock absorber that was mentioned last week.

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 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.

There you go again, feeling a bit smarter already:-)

Incubation: Heating Eggs

(Mute swan on her nest, below is her lifelong mate watching and guarding the nest.)

In order for the eggs to develop normally, they must be kept warm for considerable lengths of time.

Most songbirds incubate the eggs for about 12 to 14 days.

(Amazing that many songbirds from the day the egg is laid to fledge is about one month.)

It may be a couple days longer in some inclimate weather conditions.

For Ruby-throated hummingbirds, incubation takes 16 to 18 days on average longer (up to 21) in cooler weather.

Because mom is the only one to incubate, she must take time to feed.

This allows eggs to cool some, making for a longer incubation.

Baby also remain in the nest for three weeks (a week longer than other backyard birds), for the same reasons.

It takes about six weeks for a hummer to fledge.

Rubies lay an egg every other day and she wont start incubation until the second egg is laid.

Many experts believe the hummer would maximize reproduction if there was only one egg (one baby) to care for.

35 to 40 days of incubation for bald eagles, and this starts the day the first egg is laid.

This usually give the older chick a huge advantage when feeding time arrives.

When times are lean, the older chick will often push the younger from the nest.

Sometimes the younger chick dies in the nest and becomes a meal.

This said, I have witnessed eagle nests with three successful fledglings (good hunting grounds) at "Seney Wildlife Refuge" in Michigan's upper peninsula.

Incubation takes about 30 days for Canada geese and Mallard ducks and even larger birds like sandhill cranes.

For the giant ostrich, incubation is from 40 to 45 days.

The ideal temperature for bird eggs during incubation is 37 degrees Celsius, which is about the normal temperature of the human body.

This is interesting, because a bird's body temperature can be eight to ten degrees warmer on average.

(Now don't get the idea you can sit on eggs to hatch them.)

Nearly all birds keep their eggs warm by sitting on them.

The female usually does the bulk of incubating because she has temporarily a bare patch of skin on her underside called a Brood Patch.

The brood patch is created when the female loses feathers on her belly.

The area of skin exposed is thick and has many blood vessels.

This allows the heat from her body to be transferred to the eggs.

The brood patch is also used by the nestlings (newly hatched young) to keep warm.

(Canada Goose standing with nest.)

The normal development of the eggs can be harmed if they get too hot.

Different species have different ways of protecting eggs from overheating.

Some birds stand over the eggs to provide shade.

Ducks cover the eggs with feathers to provide shade when they must leave the nest.

Shorebirds like the Piping plover soak their feathers in water and return to sit on the eggs.

The wet feathers help cool the eggs and keep them at the proper temperature.

Still others like the house wren simply adjust the amount of time they sit on the eggs according to the temperature of the air.

On very warm days, they sit for seven or eight minutes at a time.

On cooler days they will sit for 14 or 15 minutes at a time.

In this way they control the temperature of the eggs.

Birds also turn their eggs with their beaks during incubation.

By turning the eggs, birds can apply heat more evenly to the eggs.

The incubating of the eggs varies from species to species.

In most species the female does the incubating but in some species the incubation is shared between the male and female.

The male Rose-breasted grosbeak shares incubating duties with the female.

Mourning doves incubate (male and female) by shifts.

In some species the female does all the incubating and the male brings her food, chickadees for example.

In others the female does the incubating but must leave the nest to get her own food.

When the chick is ready to come out or hatch, it is equipped with a special tool.

The Egg Tooth:

A small horny growth at the tip of a chick's upper mandible used to break through the eggshell.

This 'tooth' is lost within a few days of hatching.

When a baby bird becomes too large to absorb oxygen through the pores of its eggshell, it uses its egg tooth to peck a hole in the air sac located at the flat end of the egg.

This sac provides a few hours worth of air, during which the baby bird breaks through the eggshell to the outside.

Baby birds have a pipping muscle on the back of their necks.

It is this muscle which gives them the strength to force the egg tooth through the inner membrane of the eggshell.

'Kiwis' lack an egg tooth, instead using their legs and beak to break through a relatively thin eggshell.

Well, it's time to fly for now.

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

It's kind of fun to do the impossible.

Walt Disney (1901-1966) American Animator and Film Maker

History is full of people doing what others call impossible.

What is wonderful about god in your life,

All things are possible.....

All the time.

The bible is full of such things.

But Jesus beheld them, and said unto them, "With men this is impossible; but with God all things are possible".

Matthew 19:26

Behold, I am the LORD, the God of all flesh: is there anything too hard for me?

Jeremiah 32:27

He replied, "Because you have so little faith. I tell you the truth, if you have faith as small as a mustard seed, you can say to this mountain, 'Move from here to there' and it will move. Nothing will be impossible for you. "

Matthew 17:20

"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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