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Why Bird Legs Don't Freeze in Winter
February 16, 2015
Thank you so very much for your kind words on last week's letter "A Love Affair".
Yolanda's feeding tube come out Friday.
This is the last major hurdle from her hospitalization November 20, 2014.
We notice a few minor differences cognitively, and with her physical abilities.
For new readers, Yolanda is our daughter.
Is is brain injured and legally a quadriplegic from a car accident years ago.
She went into 'Cardiac Arrest' last November and was not breathing for a short period of time.
We rejoice and continue to give our God all the glory.
Two and a half to three months till hummingbird season here in my part of Michigan.
That's reason enough to smile.
Even in subzero conditions.
Did you participate in the 'Great Backyard Bird Count'?
With the cold and snow this time, there were some high bird counts this year.
I had a different topic in store this week, but the sub zero temperatures and sub, sub zero windchills of this past weekend brought up the topic of how birds keep warm, especially their feet and legs.
Earlier this winter, I covered the topic on birds keeping warm, however today is another lesson on bird biology.
Science in a gardening letter.
We are diverse, aren't we?
"How do birds keep their feet and legs warm (from freezing) in cold weather".
How a bird reacts to the cold depends on what kind of a bird it is and there are a variety of methods they use to keep their legs warm.
A simply way is to migrate to a warmer climate.
Many birds will simply pull their legs and feet close to their center of mass one at a time.
Thus, keeping them warm with their feathers and body heat and off the cold ground.
Some birds crouch down and cover both feet with their plumage.
In particularly cold weather, the bird can also “fluff up” its feathers, trapping air between the feathery layers to keep extra warm.
If there are other birds around, they may also huddle together when doing this.
Further, as a last resort, most birds can shiver their flight muscles to generate body heat.
Though this comes with the problem of physically tiring the bird and perhaps limiting its ability to fly.
Shivering also consumes vital energy resources.
Concerning the feet and legs more directly, many bird legs are covered with a rough, scaly skin that limits heat and moisture loss.
(This is why you never see birds stick to a metal surface.)
Not to mention the legs and feet often have an incredibly small surface area compared to the rest of their bodies, severely limiting the amount of skin actually exposed to the cold.
So what about something like a duck with positively huge, flat feet that are not only exposed to the elements, but may be submerged in ice cold water?
Birds also have another special quality given to them.
In these cases, the birds have a nifty trick up their non-existent sleeves.
Using a counter current exchange system, some birds can submerge their feet in ice cold water for hours at a time without real consequence.
The counter current exchange simply means that the bird’s veins and arteries are aligned in such a way as to facilitate heat exchange between warm blood being pumped towards the feet and the cool blood being pumped away from them.
This means that recently cooled blood from the bird’s feet is warmed before it reaches the bird’s core while at the same time blood from the bird’s core is cooled significantly before it reaches the feet.
This makes sure they aren’t dually heating the blood returning to the core and the water around their legs and feet with their core temperature blood often 104 degrees Fahrenheit, (40 degrees Celsius), or more depending on the bird.
Instead, the lace-like formation of the birds’ capillaries ensures that a lower, but sustainable temperature is maintained in the feet.
Allowing it to endure freezing temperatures around their exposed feet, while minimizing heat loss.
Further, birds with this 'God' given trait can actually control the flow of blood to their extremities using a series of muscles located at the top of their legs.
In extreme circumstances, some can even cut off the flow of blood completely, though only for a short time without damage.
They can also go the other way with it when overheated to use their exposed feet and ability to control blood flow to cool themselves down when hot.
This system is ideal for winter.
However, if a duck, goose or other bird is left in a warm environment before being put directly into a freezing one, its feet can sometimes struggle to adapt and may result in the poor little guy getting frostbite.
Yes, despite all the methods of keeping their feet warm listed above, ducks and other birds can get frostbite, and sometimes die from the cold during particularly harsh winters.
Again we are witness to one of Creation's many marvels.
Well , it is time to fly for now.
Before I go, here is your positive thought for the week.
Individual commitment to a group effort, that is what makes a team work, a company work, a society work, a civilization work.
Vince Lombardi (1913-1970) American Football Coach
Individual commitment is also required of you with God.
What better group to have in your corner than God the Father, God, the Son, and God the Holy Spirit?
Commit to the LORD everything you do. Then your plans will succeed.
Commit everything you do to the LORD. Trust him, and he will help you.
"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,
Better yet, have them sign up so they can receive their own letters.
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