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Bird Migration Starts with the Right Equipment
September 26, 2011

(Hummingbird grooming itself)

We start the first full week of Autumn.

Here in my part of Michigan, the temperatures have been a good 10 degrees below normal for much of this September.

Yes, it has pretty much felt like fall from the get go.

Peppers and tomatoes continue to produce and I just might harvest a zucchini or two this week as we have yet to have a killing frost.

Many of the flowers are winding down, however many of the annuals are just now peaking.

Red salvia (Salvia splendens) is a tender perennial from Brazil and will continue to bloom until a killing frost, if well cared for.

Many hardy perennials like Agastache will bloom until it gets to cold.

Fall bloomers like Asters, Snakeroot (Cimicifuga), Chocolate Eupatorium will add fall color for several more weeks.

Frost or no frost, they keep going until it gets too cold for them.

All the pictures today are of hummingbirds as they groom and gorge.

Preparing for their departure, which is anytime now here in my neck of the woods.

Take note at how chubby they are.

One picture gives a back view of an almost pear shape.

A couple of the pictures give a good example of how fast the
wings move, as you can see through the movement to translucent bodies and branches.

A truly amazing bird.

It is little wonder why we miss these avian marvels, and always look forward to their visits.

The first day of autumn came with little fanfare.

I'm not a big fan of fall, but I am learning to really appreciate the change of seasons and what autumn has to offer.

The days still grow shorter, the growing season will come to an end, and many of our birds take off for the winter.

Still, I am learning to appreciate the cool, crisp days,
especially when the sun shines.

We have fall colors to look forward to as the landscapes prepare for winter.

I am getting a grip on the dieing plant life, as I understand 'Nature's' plans and the need for rest.

We have fall harvests and farmers markets.

Quiet walks in parks and nature preserves.

Not to mention apples, apple cider and pumpkins.

When you learn more on why plant life goes dormant and what takes place.

When you learn more on the how's and what fors on bird migration, a person develops a new appreciation for all of Creation's wonders.

A Monarch or two still flutters by.

And much to my delight, I still have a single hummingbird.

Last week we had three in a feeding frenzy and the 24th of September is their average departure date.

It has been a few years since I have done a series on bird migration.

Why not now?

Several hundred new readers and a few of you may be new to the world of birds.

For the next few weeks I will write on birds and migration.

Hopefully you will learn a thing or two and if nothing else, be amazed.

We all know that birds have feathers and healthy feathers are required for long distant flight.

But what fuels the feathers and the muscles that move and control them?

Today's topic is on the "totally unique lungs" and breathing system of birds.


Birds are really special creatures. At least they are to me.

As long as I can recall, birds have held a special place in my life.

I'm not sure if it is the freedom of flight or the ability to go just about anywhere, or simply the colors.

No matter, birds are indeed special and in many ways unique.

You and I know they are the only creatures with feathers.

We know that with all the similarities with birds as a whole, there are also many, many differences among species.

From feeding habits and what they feed on, to nesting, migrations and where they live.

With all of this to attract us to them, and to attract them to our yards, 'Nature' has also equipped with some unique features besides having feathers.

How Birds Breathe:

Birds have lungs and air sacs, which direct air through the lungs in a one-way air flow. This one way air flow lets birds maintain a high metabolic rate.

They have lungs and tiny nostrils at the top of their beaks, used for breathing.

This is the plain and simple answer.

Like us, birds need to breathe air in and out of their lungs in order to fulfill the cycle of bringing oxygen into the body to be used in metabolism and also to take the waste CO2 away from the body.

However, unlike us, when a bird breathes the air does not go simply in and out of the lungs in a simple u-shaped path.

Instead birds have a number of large extensions called 'air sacs' and hollow (pneumatized) bones all interconnected to their lungs.

These allow the air to flow around in a grand circle meaning birds can have fresh oxygen rich air in their lungs all the time.

Also unlike us mammals, a bird's breathing is not driven into and out of the lungs by means of a diaphragm.

In birds, breathing is controlled by muscular contractions of the ribcage that reduce or increase the overall size of the body cavity and thus force air out of the various air sacs.

Air is breathed in through two nostrils situated at the base of the bill (except in Kiwis where they are at the tip of the bill and gannets where nostrils have become redundant and breathing is through the mouth).

The air enters the 'trachea' then passes down the throat until it reaches the syrinx (a bird's vocal chords).

Here the trachea divides into two 'bronchi' before passing through the lungs.

The freshly inhaled air goes first, not to the lungs, but to the abdominal air sacs.

Yes, air sacs.

These are the largest and most important of a bird's air sacs.

Some of this inhaled air goes to the posterior air sacs also.

When the bird breathes out this air moves from these air sacs into the lungs.

When the bird breathes in again, this air moves from the lungs to the interclavicular, thoracic and anterior air sacs.

When the bird breathes out a second time the air passes up the bronchus and out of the bird's system.

It takes two breaths and not one for air to pass in and out of a bird's respiratory system.

Also important to note is the fact that air passes right through the lungs, this allows for an almost continuous flow of air over the 'alveoli' and for a greater exchange rate in gases.

This exchange rate is also enhanced by the fact that bird alveoli are 10 to 100 times smaller than ours giving a far greater surface area per volume for gaseous exchange to take place.

Unidirectional flow means that air moving through bird lungs is largely fresh air & has a higher oxygen content.

In contrast, air flow is 'bidirectional' in mammals, moving back and forth into and out of the lungs.

As a result, air coming into a mammal's lungs is mixed with 'old' air (air that has been in the lungs for a while) & this 'mixed air' has less oxygen.

With less oxygen, other mammals become winded and fatigued.

(I'm winded and fatigued by walking a couple of flights of stairs.)

This plays a vital roll in migration.

Read on to see how this unique breathing is vital for all birds.

In bird lungs, more oxygen is available to diffuse into the blood at a constant rate which in turn,
keeps a bird from fatigue and from running out of breathe.

Bird Muscles:

Most, if not all of you have eaten chicken at one time or another.

Fried, roasted, baked and so on.

Some of you prefer the white or breast meat while others prefer the dark meat (legs, thighs, and wings).

So what is the difference?

Dark meat is composed of red muscle fibers (cells).

The red color comes from a high concentration of myoglobin in the fibers.

Myoglobin, like the hemoglobin in our red blood cells, binds oxygen that can be released as needed to the muscle fibers to allow them to contract.

The myoglobin increases the entry of oxygen to the muscle fibers.

Contraction of muscles allows for such useful activities as walking, flying and capturing food.

Red muscle also has an abundance of capillaries to help provide oxygen to the fibers.

These muscle fibers are quite narrow and so have a very high surface area relative to their volume.

As a result, oxygen does not have to move very far as it diffuses into the muscle cells.

The flight muscles of small songbirds (and small bats) have the highest aerobic capacity of any vertebrate species.

Red muscle fibers are often referred to as slow twitch fibers.

The fibers contract but at a relatively slow rate.

The fibers require lots of oxygen to
do their work but this oxygen is provided by the blood and stored in the myoglobin until needed by the muscles.

(Do you see how the special lungs and sacs come into play?)

Because of this, red muscles can do slow but steady work; they do not tend to fatigue.

Red muscles are excellent for sustained flight.

You can now understand that migrating birds primarily stop to feed, sleep, during foul weather or when they lose the protection of darkness.

They don't stop because they are winded or fatigued like other animals experience.

The breast of a chicken and in game birds like pheasants on the other hand, is made up of white muscle fibers.

These muscles are not well supplied with capillaries and do not contain much myoglobin to help store oxygen.

White fibers are often referred to as fast twitch muscles and are capable of very rapid contraction.

However, these contractions occur in the absence of oxygen.

After a short period of time, a waste product called lactic acid
accumulates in the cells, causing the fast twitch muscle fibers to cease contracting.

White fibers are therefore capable of a few very powerful, very strong contractions but tire quickly.

In game birds, the muscles of the thigh and drumsticks are composed of red muscle fibers.

These muscles are used for walking and scratching the ground.

The muscles do not have to act particularly quickly.

Because they are slow twitch muscles, they do not tend to fatigue.

A wild turkey or quail can walk around all day without experiencing muscle fatigue, ........ can you?

The flight muscles of these birds (the breast muscles) are white, fast twitch fibers.

When alarmed, these can use those fast twitch fibers to take off explosively.

You may have kicked one up at some time or another as it startled you as well.

However, the flight must be a short one because those white fibers quickly fatigue as lactic acid builds up in the muscles.

In most birds, breast muscles are not made up of only white fibers or only red fibers.

In most birds, the red breast muscles have a few white fibers scattered throughout.

Exceptions to the rule occur in the breast muscles of sparrows and hummingbirds that only have red fibers.

The relative quantity of slow versus fast twitch muscles is related to the particular life style of a bird.

For long distance migrants like tanagers, swallows or warblers, their flight muscles must be able to sustain long periods of use.

White fibers would be poorly suited to the task so it comes as no surprise that the breast or flight muscles of these birds are mostly red muscle.

On the other hand, the great power but short duration of white fiber contractions makes white breast muscles suitable for birds that need to take evasive action in flight to avoid predators or to fly through thickly forested habitats.

This holds true for many birds of prey that rely on short bursts and quick take offs.

It also helps to understand the important requirements and abilties these birds have to soar for hours on end.

The size of the breast muscles in a bird is related to its flying ability.

In birds that are powerful fliers, over 20% of the bird’s weight is breast muscle.

In birds that do not fly, less than 10% of the body weight comes from the breast muscles.

The skeletal muscles play another important role.

In the winter, when the temperature falls below a critical level, the skeletal muscles begin to shiver.

These rapid, involuntary contractions release heat to help the bird maintain its body temperature.

This too requires a constant supply of oxygen.

Well, there you have it.

Besides healthy feathers, the proper breath support is required for migration.

It just so happens that Creation has supplied birds with everything they need.

It's time to fly for now.

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

God Bless.

Love always creates, it never destroys.
In this lie's man's only promise.

Leo Buscaglia

Read or listen to any of the late Mr. Buscaglia's material, and you can't help but smile

“Let all that you do be done with love.”

(1 Corinthians 16:14)


"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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