Furcula – previously known as the “merrythought”…
Pulling on the wishbone to see who gets the long end when it breaks and then has their fondest wish granted has been a festive holiday tradition for centuries. It came to us from the English in the 1600’s (at that time they called the wishbone the “merrythought”) but the “magic” attributed to that oddly shaped bone came to them from the Romans who got it from the ancient Etruscans in Italy. Who doesn’t have fond memories of kids (and sometimes adults) squabbling over who gets a chance at the wishbone, since only two can participate?
By I, Toony, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2321740
The actual name of the wishbone is the furcula – seen in red in the stylized rendition of a bird’s skeleton above. It’s formed by the fusion of the two clavicles (collarbones) in most birds and some dinosaur skeletons. In humans our clavicles are unfused.
One of the primary functions (there are several) of the furcula in birds is to make flight more energy-efficient. The bone is incredibly flexible (as impatient humans have learned when they try to break the wishbone before it has been dried and rendered brittle) and that flexibility contributes to its function. When a bird’s wings are powered down in flight by the huge pectoralis muscle the ends of the furcula are stretched apart which loads them with “spring energy”. Then when the wings begin the upstroke the stored energy is transferred and helps to move them in an upward direction as the ends of the furcula return to their previous shape.
It’s complicated – several muscles and tendons are involved but what an ingenious partial solution to the vexing problem of providing enough energy to power flight without requiring even larger muscles which would add weight and make flight even more energy consumptive. The ends of the furcula are stretched apart by as much as 50%. They then contract during the upstroke – acting like a spring and powering the upward movement of the wings.
So the next time you’re admiring the power and grace of a bird in flight (such as this male Northern Harrier) keep in mind that the “wishbone” is partially responsible for their aerial magic. Evolution is a marvelous thing!
Ok, enough academics on this Thanksgiving morning. I hope each and every one of my readers has a wonderful and joyous holiday with family and friends and if you partake of the wishbone tradition may you get the long end of the bone and your fondest wish come true.
As for me – yes, I’m having turkey for Thanksgiving dinner and I already know what I’m going to wish for if I win the tug on the bone. During a wet and heavy snowstorm last night I heard a loud crash and simultaneously felt my house shudder and shake as if a vehicle had crashed into it. I got out of bed, dressed, grabbed a powerful flashlight and went outside in the snow to investigate and my biggest fears were realized. A huge branch from my enormous elm tree broke off and crashed onto my roof. That branch is as large as some mature trees.
My wish will be that there’s no significant damage to my roof. I won’t know until later today when it hopefully warms up enough to melt the snow up there so I can safely climb up on the roof and investigate. Wish me luck…