Yearly Archives: 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)

Eating Crow

Crows & Ravens


If I was to place a bet on crows I’d wager they didn’t spend last night in the plane trees on University Place in Oakland.  I’d win this bet because of what I found there less than 24 hours ago.

Yesterday morning I got a call from a Pitt employee who tracked me down out of concern for the peregrines.  Marian had found a very large raptor standing on the ground near Soldiers and Sailors Hall on University Place.  The bird would not fly away and there were feathers scattered on the ground beneath its feet.  She was concerned that this was one of the peregrines and that it was injured and unable to fly away.

The situation sounded like a red-tailed hawk on a kill but you never know.  I was happy to help and went over to check.

As I arrived at University Place I noticed a lot of crow poop on the sidewalk beneath the London plane trees.  The closer I got to the site, the more poop there was. 

When I reached the place Marian described I didn’t find a large bird on the ground but I could tell exactly where he’d been.  Right next to the sidewalk was a big pile of crow feathers, a few crow bones and a crow’s skull and beak.  Whoa!  Someone had been eating crow!

I imagined the fear in the flock when that raptor arrived.  I’m sure it scared the poop out of them and they left in a hurry.  No wonder the sidewalk was gross.

Now there’s one less crow among the 10,000+ who roost in Pittsburgh and those still living can see how he died. 

I can pretty much guarantee the crows won’t be back there soon.

(photo by Chuck Tague)

Prairie Falcon at Mud Level Road

Beyond Bounds, Birds of Prey


I usually don’t chase rare birds because I am so disappointed when I drive a long way and don’t find what I came for, so in December 2005 when Andy Markel reported a juvenile prairie falcon in the open fields of Cumberland County north of Shippensburg I did not go see it.

Over the next few weeks Andy and others found and photographed the prairie falcon again and again.  It was so far out of range that many wondered if it was a falconer’s bird but no one could prove it.  The bird stayed through the winter and then was gone.

Prairie falcons (Falco mexicanus) are western birds of cliffs and open country.  They’re the same size and shape as peregrines except that they’re pale brown and white with dark axillaries (armpits) and pale heads.  They range from California to Colorado, from southern Canada to Mexico. They never come to Pennsylvania.

But this one does.  Every winter the prairie falcon returns to the same place on Mud Level Road.  Now, of course, it’s an adult.  In February 2008 it was found so easily that many birders made the trek to see it and even discovered that it roosts at a quarry a mile away from its daytime haunts.  (Prairie falcons like cliffs just as much as peregrines do.)

Still I did not go to see it.  The 3 hour drive from Pittsburgh was too long for the disappointment I was bound to encounter.

But this year the falcon came back early — November 20 — and I was going to be in Hummelstown for Thanksgiving, only an hour away.  Saturday morning, November 27, was my only chance to chase it.

Long before dawn I drove to Cumberland County and found two other birders already at the intersection of Mud Level and Duncan Roads.  Neither had found the bird but with more eyes on the sky we stood a better chance.

Soon we saw a falcon hazing the pigeons northwest of Mud Level but even through a scope the bird was impossible to identify.  Jonathan Heller and I drove to Brinton Road for a better look but could not relocate the bird.  Mike Epler stayed behind, then drove the circle.  No luck.

Back and forth we searched.  Jonathan and I tracked a falcon that didn’t look quite right but it was our best candidate.  We finally caught up to it just as it landed in a tree on Brinton Road.  We screeched to a halt, jumped out of our cars and identified … a merlin.

At any other time and place a merlin is a good find but we were disappointed.  This was made worse when Mike drove up and told us he had just seen the prairie falcon at Mud Level and Duncan.  He had watched it retrieve a mourning dove dropped by a harrier, then perch and eat the prey close enough for a great look.

Aaarrrgg!  We went back to our starting point but the bird was gone.

Jonathan was preparing to leave so I took a slow drive down Mud Level Road contemplating the ephemeral nature of rare birds.  I told myself that on this trip I’d heard horned larks and seen a merlin, kestrels, northern harriers and red-tailed hawks — and that should be enough.  Sigh.

No point in looking anymore.  Sigh.

I drove away slowly down Duncan Road.

A pale brown hawk, very pale, on a hay bale, caught my eye.  It had its back to me and was eating.  Oh my!  I pulled off the road and parked near the hay bale.  I rolled down the passenger window and had an excellent view of the prairie falcon as it ate a bird.

The falcon looked around, his cere and eyerings yellow, his legs brighter yellow, his head quite pale.

Though I stayed in my car I made him nervous.  He bobbed his head, then picked up his prey and flew to another hay bale.  In flight I saw his dark axillaries.  Again he was nervous, flew down to the ground, then eventually northwest across Mud Level Road.  Good bird!

I’ve now seen every falcon that normally occurs in North America except the aplomado.  (It occurs from Mexico to South America, rarely in the southwestern U.S.)

Needless to say the bird in this photo is not the one at Mud Level but it captures his look and posture.  For an even better look, click here for a flight photo and you’ll see the dark feathers under the wing.

(photo of a prairie falcon by Matt MacGillivray via Wikimedia Commons. Click on the photo to see the original)

Quiz: What happened here?

Quiz


Today’s quiz should be easy for anyone who lives in Pennsylvania. 

I found this damaged hemlock in Moraine State Park last weekend. 

  • What happened to this tree?
  • Who did this?  And why?
  • Does this happen to trees of any size?
  • Does this normally happen to hemlocks?
  • Hardest question:  What significance does tomorrow, November 29, have for this particular tree?

Post a comment with your answer.

p.s. I will be traveling today so you’ll see all the comments appear at once when I get to a computer and approve them.

(photo by Kate St. John)

Beyond Bounds: Brant

Beyond Bounds, Water and Shore


Here’s a beautiful picture of a bird we rarely see in southwestern Pennsylvania.  When we do it’s alone, flown off course while its companions migrated to the Atlantic coast on a route far north of Pittsburgh.

This is a brant, a small goose that nests in the Arctic and winters at the coast.  It resembles a Canada goose except that it’s much smaller, has a stubby bill, the shortest tail of any goose, and a dark head, neck and chest.

Sometimes brant, especially lone birds, hang out with Canada geese.  This may have saved them from extinction.  In the early 1930’s the brant population declined dangerously because the only food they ate — a marine plant called eelgrass — was in short supply.  Then they changed their diet to include grass and grain from agricultural fields, a habit they may have learned from Canada geese.  But they still prefer eelgrass.

If you want to see a lot of brant, visit the coast in winter.  Otherwise the only reliable place to find them in Pennsylvania is at Lake Erie during their October-November migration. 

Bobby Greene photographed this bird on Lake Erie at Conneaut, Ohio.

(photo by Bobby Greene)

Anatomy: How do birds fold their legs in flight?

Bird Anatomy
Diagram of bird skeleton showing how legs fold for flight (image from Wikimedia Commons)

26 November 2010

Today’s anatomy lesson was inspired by Michelline who asked why she sees only peregrines’ neatly folded talons when they fly.  Where do the rest of their legs go?

The bones in birds’ legs are of nearly equal length and the hinges are opposite like an accordion.  This means birds can fold their legs to lower their bodies straight down to sit on eggs and they can retract their legs to a flat position in flight. 

To illustrate this I’ve highlighted the legs in red and numbered the joints: 

  1. From the body to joint #1 is the thigh (femur)
  2. Joint #1 to #2 is the shin (tibiotarsus) and calf (fibula)
  3. Joint #2 to #3 is the foot (tarsometatarsus)
  4. Joint #3 to the end are toes.

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For most birds, even when standing, the thigh is hidden in the body feathers. Birds’ legs are much longer than we think! See how long a juvenile peregrine’s legs are in this slideshow.

The blue arrows above show how birds fold their legs when they fly.  In step (a) the thigh and shin fold up flat to the body and are hidden in the body feathers.  In step (b) the toes may do one of several things.

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When you see only a peregrine’s yellow toes in flight it’s because his legs and feet are covered by his body feathers. 

Aeronautical engineers learned from birds.  Watch a jet take off and you’ll see it retract its “legs” under its wings.

(bird skeleton by W. Ramsay Smith and J S Newell, 1889, via Wikimedia Commons, altered to illustrate the leg. Click on the caption to see the original.)

Winter Weeds: Indian Pipe

Winter Weeds & Trees


Here’s a strange plant that grows in oak or evergreen forests, the shadier the better.

Indian Pipe (Monotropa uniflora) is a parasitic plant in the Wintergreen family whose summer and winter forms look quite different.

In summer the plant is all white, almost translucent, and its flowers bend down to face the forest floor.  It has no chlorophyll and no leaves, just scales on its stem, because it lives on nutrients from fungi in the humus (leaf litter).  

Indian Pipe’s white appearance earns it the nickname Ghost Plant.  Click here to see its summer form. 

In winter Indian Pipe is brown and stands about six inches tall.  Its flower head is now a five-sided woody seed capsule that points straight up.  The scales on its stem are wrinkled and look like the remnants of leaves.

Because it’s a perennial Indian Pipe is likely to bloom in the same place next year. 

Remember where you found it.  Come back in June to see the ghost.

(photo by Dianne Machesney)