Monthly Archives: December 2010

How Do They Sleep Without Slipping?

Bird Anatomy
Topography of a Bird, Chester A. Reed, 1915 (public domain via Wikimedia Commons, image altered)

One of the most fascinating things about birds is that they can perch while asleep and not fall off the branch. 

We know from experience that our hands can grasp while awake, but when we fall asleep our hands relax and we drop what we’re holding. 

Why doesn’t this happen to birds? Why don’t they fall off the perch when they fall asleep?

Songbirds’ feet work quite differently than our hands.  Perching birds have a long tendon that starts at the calf muscle, extends around the back of the ankle and travels down the insides of each toe.  When the bird squats the tendon is pulled tight and it, in turn, pulls the toes closed.  When the bird stands tall, the tendon relaxes and the toes open. 

In the illustration above I’ve drawn the calf muscle and tendon in red.  The “ankle” is the sharp bend in the bird’s leg shown just under its wing.  According to Frank B. Gill’s Ornithology, songbirds also have a special system of ridges and pads between the tendons that assist the natural locking mechanism. 

So when a songbird relaxes, its feet grasp more tightly. Songbirds sleep without slipping.

(Image altered from Chester A. Reed, The Bird Book, 1915.  In U.S. public domain via Wikimedia Commons.  Click on the caption to see the original.)

Penguin Cam!

Books & Events


Are you starved for live bird activity on your computer?  Do you miss the peregrine webcams?

Well, here’s something to pique your interest while you wait for spring.  The National Aviary has installed a Penguin Cam at their African penguin exhibit.

If you haven’t met these penguins yet you’ll soon find out they’re photogenic, sociable and cute. 

Because their native climate in South Africa is similar to Pittsburgh’s the penguins live outdoors with glass viewing areas for visitors.  The clear cylinder at the back of the image is one such viewing area so don’t be surprised if you see a person in it.  There’s no sound on the video but you can watch the penguins all night because infrared light illuminates the scene. 

If you’re familiar with the Aviary’s peregrine falconcams, you’ll notice the Penguin Cam is similar but better than ever.  PixController helped set it up, Wildearth.TV is streaming, and the new equipment behind the scenes is more reliable.  The picture is sharper, the colors brighter and the image is much less likely to freeze.  It’s such a good arrangement that this equipment is planned for the falconcams next spring. 

Check out the Penguin Cam.  Try out the new chat.  Click on the image above to watch the action. 

After you meet the penguins online I’m sure you’ll want to see them in person at the National Aviary. 

(screenshot of the National Aviary’s Penguin Cam)

p.s.  Scroll down the Penguin Cam webpage to learn more about African penguins and see a short video.

Winter Weeds: Common Milkweed

Winter Weeds & Trees


In late fall when I’m hiking near fields and roads I often see plants with big seed pods and white fluff tumbling out.  The plants are milkweed but they look quite different from their summer appearance. 

Common milkweed is a conspicuous perennial in winter because its large, warty, seed pods stand high on three to five foot stems. 

The pods are fat at the bottom, pointed at the top and split open on their long edge to reveal soft, silky fluff carefully layered inside.  Each wad of silk is attached to a flat, brown seed.  

When exposed to the weather the silk becomes fluffy and eventually flies off the plant, carrying its seed cargo as far as it will go. The pods stand high to send their bounty on the wind.  

To me one of the great mysteries of milkweed is that it looks so different in winter.  In summer it’s weighed down with large, drooping, pink flower umbels but now the pods stick up alone and there are far fewer of them than the number of flowers in the umbel.  I have read that only one flower in each milkweed umbel produces a seed pod.  (Do any of you know how this works?)

Common milkweed is a great plant for attracting monarch butterflies to your garden.  If you already have milkweed you can leave the stems standing over the winter and watch where the seeds fly. 

When you’re ready to clear them away in the spring, Marcy Cunkelman suggests you save the dried stems and put them out in mid-April for the birds to use as nesting material.  The fibers are strong and peel off in strips.  They’re quite a favorite of Baltimore orioles.

(photo by Marcy Cunkelman)