WHY DON”T SLEEPING BIRDS FALL OUT OF TREES?

Posted by Roger Lederer   @   18 August 2010 2 comments

           Birds have a
skeletal system with a number of adaptations for their way of life. Flying
especially requires a number of adaptations to make the birds’ bones lighter
and stronger. Many bones are fused into one, some are hollow, and most have
internal struts for strength. Flying birds have a keel extending from their
sternum to which the flight muscles are attached. If you debone chicken
breasts, that’s the big bone you remove in the process. Flying birds, swimming
birds, and flightless birds all have special skeletal adaptations.

Ever wonder why a sleeping bird
doesn’t just pitch forward and fall off the branch it is perched on in the
middle of a nap? How about the birds perched in trees and shrubs or on power
lines on a windy day? Are they just hanging on for dear life, hoping they don’t
get blown off? The answer is that songbirds are well adapted to their perching
life. In fact, in ornithological parlance, the terms “songbirds” and “perching
birds” are interchangeable.

3272-chestnut-napedforktail-for.jpg

You may have heard of the
Achilles’s tendon, the tendon that extends from our calf muscle around the back
of our foot to the heel. Reach down right now on your leg  and feel it. This tendon enables us to flex
our foot up and down – try it. If the Achilles tendon were injured, the foot
would be almost immobilized. This is how, in mythology, Achilles was killed -
Paris shot an arrow into Achille’s tendon.

Look at this diagram of a bird’s
leg. There are the toes, of course, but notice that the long bone above the
foot is actually the ankle (tarsometatarsus)! The tibia and fibula, which make up our lower leg
bone, are hidden by the bird’s feathers, as is the femur. So while humans have
two long bones leading from the hip to the foot, birds have three.

3270-tendon.gif

         In birds, the
Achille’s tendon runs from above the ankle to the back of the foot and then along
the bottom of the toes. When a bird lands on a branch, the ankle bends and the
Achilles’ tendon is stretched. When the tendon stretches, it pulls on the toes
and curls them around the branch. There is no muscular effort involved in
holding onto the branch – it’s automatic. When the bird takes off, the legs
straighten, the tendon relaxes, and the toes release their hold on the branch.

3271-bird leg.jpg

          Well, now you
might wonder why you don’t occasionally see a dead bird sitting on a branch,
having died in its sleep from exposure to cold or just old age.In death, the muscles initially relax and the bird just falls out of the tree.
In another blog I’ll tell you why you don’t see as many dead birds as you do
mammals, either in the woods or as roadkills.

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2 Comments

Comments
Aug 18, 2010
1:07 pm
#1 Onevike :

Amazing.

Now that is something that could only have been designed by an intelligent designer who had forethought of how he wanted them to live. God designed them in such a way, they did not evolve into growing the tendon for safety reasons.

In my opinion there is no reason for a bird to evolve in such a way. It would seem that the most logical way to evolve, if the bird did not already have that design, would be to just return to a nest for safety and sleep.

Your thoughts?

Oh yea, I am not attempting to draw you into an evolution vs creation debate.

I truly would like to know what you think about the reason why a bird would evolve in such a way as apposed to their minds evolving into learning a habit of returning to a nest to rest instead, like most animals do.

Reply: You may think getting into a nest at night is the best way to get rest but nest holes are scarce and predators like jays and squirrels and others can raid the nests and the birds inside have no way to escape. So sleeping on a branch outside is safer from that respect. For every need (food, water, nest, mates), there are many alternative ways of obtaining it.
Roger

Sep 24, 2012
10:25 am
#2 cannada :

> In my opinion

There’s your problem. Evolution is not a matter of opinion.

Sorry, comments are closed.

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