Tag Archives: rete mirabile

OUR GOOD HARBOR BEACH PIPING PLOVERS COPING WITH WINDSTORMS AND COLD TEMPERATURES

All three PiPls, Mom, Dad, and the Bachelor, are finding drifts of sand, clumps of dry beach grass, and this morning, even a clam shell, to hunker down behind to get out of the way of the harsh winds. They are also doing a great deal of standing and hopping around on one leg. I hope the wind dies down and soon so we can all enjoy more seasonably spring-like weather!

Mama taking a nap behind a clump of beach grass, and standing on one leg.

Papa standing on one leg even while doing wing stretches.

And what Piping Plover scene would be complete without a bachelor (an unmated male). I hope we get a “new girl” this summer!

Why do birds stand on one leg? “The short answer is that for the simple reason that you put your hands in your pockets when cold, birds stand on one leg to conserve heat. Birds also stand on one leg to relax muscle fatigue in the retracted leg.

The long answer is that birds’ legs have a blood flow referred to as “rete mirabile” that minimizes heat loss. The arteries that transport warm blood into the legs are next to the veins that return colder blood to the bird’s heart. The arteries act as a heat exchanger and warm the veins. Because the veins also cool the arteries, the bird’s feet are closer to environmental temperature and thus don’t lose as much heat as they would if they were at body temperature. By standing on one leg, a bird reduces the amount of heat lost through unfeathered limbs.

Birds that have short legs, such as Mourning Doves, do not need to stand on one leg because they have fleshy feet and they can snuggle down so that their warm belly presses against their feet.” Reposted from “Why is Little Chick Missing a Leg.”

If you see Gloucester’s dog officers, Teagan and Jamie, please thank them and let them know what a great job they are doing. Off and on throughout the day, they are walking the beach, talking to the dog owners who continue to bring their dogs to the beach, and handing out tickets.

WHY IS LITTLE CHICK “MISSING” A LEG?

Why is Little Chick “missing” a leg? That is a question I am often asked when filming Little Chick and an interested person stops by to visit our GHB Piping Plover. Or the comment, “Oh, no, he is one-legged!”

If you see Little Chick resting in the sand and he is standing on one leg, know that he is doing it very purposefully. The short answer is that for the simple reason that you put your hands in your pockets when cold, birds stand on one leg to conserve heat. Birds also stand on one leg to relax muscle fatigue in the retracted leg.

The long answer is that birds’ legs have a blood flow referred to as “rete mirabile” that minimizes heat loss. The arteries that transport warm blood into the legs are next to the veins that return colder blood to the bird’s heart. The arteries act as a heat exchanger and warm the veins. Because the veins also cool the arteries, the bird’s feet are closer to environmental temperature and thus don’t lose as much heat as they would if they were at body temperature. By standing on one leg, a bird reduces the amount of heat lost through unfeathered limbs.

Birds that have short legs, such as Mourning Doves, do not need to stand on one leg because they have fleshy feet and they can snuggle down so that their warm belly presses against their feet.

Forty-one-day old Piping Plover standing on one foot.

Our Little Chick is doing beautifully. I checked in on him briefly at day break and again at 9:30 this morning. Foraging, resting, flying (the longest distance yet, from the enclosure to the back of the Creek.) Both last night (thank you Heidi Wakeman) and this morning, I found him in the enclosure. I think our Little Chick is extra super smart to recognize the roped off area as his “safety” zone. We are grateful to the community and to Gloucester’s conservation agent Ken Whittaker for allowing the roping to remain in place.

The light was very low and the photo is a little too softly focused, nonetheless I liked the image of Little Chick taking off.

Why Do Herons Stand on One Leg?

Great blue Heron one leg -2©Kim Smith 2013Great Blue Heron at Good Harbor Beach ~ Click to view larger

There are several theories as to why birds, especially large wading birds such as herons and flamingoes, stand on one leg, or “unipedal resting” as scientist like to refer to the trait. The seemingly most convincing and best-proved theory is that birds stand on one leg to conserve body heat. It is shown that birds stand on one leg more often when wading, which again points to the thermoregulation hypothesis because water draws away more body  heat.

Great Blue Heon one leg Good Harbor beach ©Kim Smith 2013 copyGreat Blue Heron (Ardea herodias)

Standing on one leg is not necessarily a sleeping and resting habit. I have filmed Great Blue Herons and Snowy Egrets meticulously preening while standing on one leg. The characteristic is not limited to large wading birds; species with shorter legs, including ducks and swans, also stand on one leg. Another popular theory suggests that wading birds stand on one leg to look less suspicious to aquatic prey.

wp4768443cCenter of gravity and line of gravity

wp0e750516Goose standing on one leg

To read more about avian sensory physiology, visit the website of Professor Dr. Reinhold Necker. Additional images courtesy Professor Necker’s website.