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Egg Incubation
May 07, 2018

(Full Moon early last week.)

Keet, and Snick, Snick had a spring hair cut this past Tuesday.

Next couple of weeks are filled with various appointments.

Like many of you, I'm sure you have a couple times a year when all the appointments pile up.

Most of this is planned, as we try to free up certain times of the year for ourselves, if possible.

You too?

May is my favorite month of the year.

Not December, (Christmas Season).

Not July, for all it has to offer.

Not even the relaxed and colorful autumn season.

It is May, and the start of this May did not disappoint me.

May offers all the color, song, and surprises that Christmas/Holiday season offers.

May offers all the wonders and sparkle that July and summer brings.

As busy as times are in May, it even brings me joy, relaxation, vibrant colors, and cool evenings, just like The fall can.

Though plant life is slow to emerge this May, due to a colder and snowier April, everything is exploding to life right now.

With very few exceptions (tree swallows were later this past April). wildlife hasn't missed a beat.

This past week, White-crowned sparrows have come to visit.

They will stay a couple of weeks before moving north to their breeding grounds.

Rose-breasted grosbeaks, Baltimore orioles, House-wrens, and Ruby-throated hummingbirds have all appeared this past week.

White-crowned sparrows, and Orioles in good numbers.

Both species are quite active and full of song.

As are the Grosbeaks and Wrens.

he toad I pictured last week, still buried and semi dormant ........

Along with thousands of other toads, have made their way to pond, swamps, and streams.

Mating season is on and the toad chorus fills the air.

Green and Great Blue Herons, perch and stand in the shallows, as they feast on toads right now.

Sometimes getting a two for one special (mating pair).

Without missing a beat, Nature marches on.

All the pictures are from this past week.

Okay, there is some redundancy from last week's letter, then to this week's topic.



(Female Red-Belly Woodpecker.)

If you read last week's letter, this first part will be familiar to you.

“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 invisable 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.

Incubation: Heating Eggs

(Female, Rose-breasted grosbeak.)

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 in cooler weather.

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

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

35 to 40 days 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.

I digress.

(White-crowned sparrow.)

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 about 98 degrees F. (37 degrees C), which is about the normal temperature of the human body.

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

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

The female usually does the 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.

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

Side Bar:

Incubators can be as simple as a light bulb, and a cup of water with a simple dome.

Eggs must be turned regularly by hand (Mother bird does this all day long with bill and feet).

Incubators can be purchased for hobby farmers, rehabilitators, and for commercial use.

These incubators do all that is required for successful hatches.

They also come with a price tag.

(Male, Rose-breasted grosbeak.)

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 killdeer 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 incubating is shared between the male and female.

Examples are:

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

In some species the female does all the incubating and the male brings her food (Chickadees).

In others, the female does the incubating but must leave the nest to get her own food (hummingbirds), this is why incubation times are days longer for this these tiny birds.

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

The Egg Tooth:

Creation provides 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.

(Baltimore oriole.)

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.

Notice the grape jelly in the bill of the bottom two pictures.

Well, it's time to fly for now.

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

"When we do the best we can, we never know what miracle is wrought in our life, or in the life of another".

Helen Keller (1880-1968) American Writer

How true.

Our actions not only affect us, but those around us.

It's your choice.

"Whatever you do, work at it with all your heart, as working for the Lord, not for human masters, because you know that you will receive an inheritance from the Lord as your reward. It is the Lord Christ you are serving. "

Colossians 3:23

"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.

A Blessed week to you .

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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