Monthly Archives: October 2010

Happy Halloween!

Here’s a trick: You won’t find these dragonflies in western Pennsylvania in late October. 

The Halloween Pennant, named for his orange and almost-black colors, is only here in the summer. 

Here’s a treat: If you live in Florida, Halloween Pennants are present year-round.  For you, today’s a good day look for this timely insect.  You’ll find him on the tip of a weed, riding the wind.

(photo by Julie Brown.  Click on the photo to see the original.)

Almost November, what will we see?

Yesterday morning was cloudy, cold and blustery.  As I waited at the busstop hundreds of grackles flew south over Greenfield.  Perhaps they were leaving the roost.  Perhaps they were leaving town.

In only two days it will be November.  The variety of birds is dropping though the number of crows, robins and starlings is growing.

Soon the north will freeze and migrating ducks and swans will stopover on Pennsylvania’s lakes.

Yesterday Karen DeSantis reported a flock of tundra swans over Westmoreland County, the first this fall.  I can hardly wait to see a V of swans myself.

What else will we see in November?

There’s a list on my phenology blog “What to Look For in Early November” and at Chuck Tague’s “Welcome to the Dark Side.”

(photo of migrating tundra swans by Chuck Tague)

Anatomy: Where Are Their Teeth?

Diagram of bird digestive system (linked from
Diagram of bird digestive system (linked from

As I said last week, birds have the same basic internal equipment that we do but the location and shapes of their body parts are modified because they fly.

So here’s a puzzle.  Where are their teeth?

Millions of years ago the ancestors of birds had teeth but modern birds don’t have even a vestigial tooth.  Yet they eat food that ought to be chewed: meat, nuts, and entire mice and fish swallowed whole.

Birds do indeed “chew” their food but not in their mouths.  Teeth are heavy equipment for the front end of flying animals and if they had to escape suddenly while chewing a big meal, the food would add extra weight to their heads, a real challenge to flight.

Birds’ bodies have an elegant solution to these two problems.  The chewing mechanism and main holding compartment are the same organ, the gizzard, located at the center of gravity under the wings.

The gizzard is a muscular stomach that breaks up food by grinding it with the grit birds eat to aid digestion.  The gizzard grinds and turns the food among the grit, breaking it into smaller bits the same way we chew with our mouths.

As you can see from the diagram, the gizzard is the third digestive organ in most birds.  The first is the crop, a bulge in the esophagus where food waits to be processed.  The second is the glandular stomach or proventriculus where enzymes break down the food before passing it to the gizzard where it’s “chewed.”

So now you know.  Birds’ teeth are on the inside.

(image of a bird’s digestive tract, linked from Fernbank Science Center in Atlanta, Georgia.  Click on the image to read more about birds’ digestion.)

Why the Leopard Got His Spots

In 1902 Rudyard Kipling answered How the Leopard Got His Spots.

According to Kipling, the Ethiopian and the Leopard originally hunted on the High Veldt where they and their prey matched the plain, sandy landscape.  Their prey moved to the forest but when the Ethiopian and Leopard followed them there, the animals they hunted were camouflaged while they “show[ed] up in this dark place like a bar of soap in a coal-scuttle.”  They couldn’t catch a thing.

“The long and the little of it is that we don’t match our backgrounds” said the Ethiopian, so he changed the color of his skin and offered to help Leopard change too. “The Ethiopian put his five fingers close together (there was plenty of black left on his new skin still) and pressed them all over the Leopard, and wherever the five fingers touched they left five little black marks, all close together.” 

So, says Kipling, that’s how the Leopard got his irregular spots.  And why?  He needed camouflage in the forest.

More than 100 years have passed.  Can science support this story?

Last week the BBC reported on a new study that confirmed Kipling’s “why,” but not his “how.” 

Using mathematical models, scientists analyzed the pattern complexities of wild cats’ coats and correlated the complexity levels to the cats’ lifestyles.

Do wild cats have spots and stripes for social reasons?  Do the patterns attract mates or repel rivals?  No.  The models showed that cats living in trees and at low light levels are the most likely to have complex and irregular coat patterns.  Notice how the tree-dwelling leopard’s spots are similar to the dappled leaves behind him.

Which brings me to a cat I know very well.  She is not wild, she does not live in trees, and she doesn’t have to operate at low light levels.  Nevertheless Emmalina has four colors on her coat (white, beige, taupe and black) in an irregular pattern of blotches and stripes. 

In our house we’ve learned this pattern makes her disappear when crouched on the kitchen counter, an amazing adaptation for modern life.

(leopard photo from Wikimedia Commons.  Emmalina’s photo by Kate St. John.)

Crabapples and Rain

Thank you, everyone, for your comments, emails and phone calls about yesterday’s quiz.

My local experts — Marcy Cunkelman, Dianne Machesney and Chuck Tague — agree that the tree is a crabapple.   My photo didn’t provide enough information to identify the cultivar but Marcy suggested a Sargent’s Crabapple, Dianne gave us a list and Chuck Tague emailed this comment:

“Dianne and Marcy are correct.  It is one of the ornamental crabs.  It resembles the trees at Chatham Village in Mt. Washington, Showy Crabapple “Malus floribunda”.  The top of one is close to my second floor office window. It is not a favorite of birds until after the first hard frost.  Then, usually a week or two before Thanksgiving, swarms of fruit-eaters descend on the tree.  American Robins and Cedar Waxwings bounce from crabapple to crabapple in a frenzied feast.  Mixed in are House Finches and House Sparrows.  Eventually a brigade of European Starling swoops in and the fruit is stripped clean in a few hours.”

Chuck sent a photo of a cedar waxwing tossing back a crabapple, but I chose this one of a robin in the rain — on Chuck’s crabapple tree — because it ties two themes together.

Yesterday’s storm and heavy rain reminded me that there’s a link between weather, birds and food.  We might guess that heavy rain puts birds under stress.  Now we have some proof.

Alice Boyle of the University of Western Ontario studies white-ruffed manakins in Costa Rica.  They’re fruit-eating birds the size of chickadees who, like chickadees, must eat all the time and, like chickadees, change elevation in the winter.

Winter in the Costa Rican rain forest isn’t cold but it’s very, very wet.  Alice Boyle and her colleagues discovered that when particularly long, heavy rain storms plagued the area, the white-ruffed manakins migrated to lower elevations.  Blood tests of rain-affected birds showed they had high levels of stress hormones and were burning fat.  In other words, they were hungry and stressed out.

Boyle says that the stress of rain may be what prompts the birds to fly downhill to drier ground, “These rainstorms have really strong effects, both behaviorally and physiologically, in ways that nobody knew before.”

Her study might not translate to all birds, but it supports our guess that rain means stress.

Read the article and see a picture of the white-ruffed manakin here.

(photo by Chuck Tague)

Quiz: What tree?

I believe I know the answer but I’m not absolutely sure so I’m asking you, dear readers.

What tree is this with such bountiful fruit?  It’s a short, ornamental tree, probably non-native.  Notice how the bright red fruit hangs in clusters from the branches.  I’m amazed the birds were not eating it yet.

Want to see it for yourself?  It’s one of several such trees in Schenley Park on the right side of the walk to the ice rink near Schenley Oval.

If you know its name – or even have a wild guess – leave a comment to let us know.

(photo by Kate St. John)

Vulture Facebook

Human faces turn red with anger or embarassment and pale with fear.  Do other animals do that?

Well, yes.  Some vultures can rapidly change the skin color of their bare faces and throats in response to peers and rivals.  Scientists in Namibia observed interactions among lappet-faced vultures at feeding sites and found that these birds have their own “vulture facebook” signals.

The scientists learned that lappet-faced vultures with pale skin are at the bottom of the pecking order, even lower than juveniles.  Those with bright red skin, as seen on the throat of the vulture pictured here, are dominant over pale-skinned and juvenile birds and vultures with blue throats were dominant over all.

This knowledge adds a whole new dimension to vulture watching.

Do our turkey vultures do this?

I don’t know.  Maybe they don’t use (vulture) Facebook.

(photo linked from Science Daily, credit: iStockphoto/Johan Swanepoel. Click on the photo to read the Science Daily article.)

Turning gray

Gray squirrels are, of course, gray — that’s how they got their name — but did you ever notice that in the summer they’re actually rather brown?

From March through June gray squirrels molt into a brown or tawny pelage that blends well with their summertime surroundings.  Then in September and October they molt again, this time into paler, grayer winter coats so they’re ready when the cold winds blow.  My backyard squirrels are making this change but their faces and ears are still brown. 

Lately I’ve seen the squirrels on frequent caching expeditions up and down the street because my neighbor has a prolific black walnut tree.  I’m sure the squirrels are burying walnuts but I only see evidence that they’re eating them.  They leave behind little piles of broken shells and a permanent black stain on the cement.

I wish they wouldn’t pick my front steps for their walnut feasts but I can understand their urgency. 

Winter’s coming.  It’s enough to turn a squirrel’s hair gray.

(photo from Wikimedia Commons.  Click the photo to see the original.)

A Little Fall Color

I think the colors are subdued this fall because we’ve had a drought.  Even so I saw some nice red leaves on Thursday evening in Schenley Park.  It’s not a good picture but you get the idea.

And… the crows are back!  Last night I saw more than 300 flying to the roost.  This morning I counted about 1,000 flying southwest over my neighborhood.

Glad to see they made it to Pittsburgh just in time for tomorrow night’s program.

p.s. I took a walk on the Upper Panther Hollow Trail this afternoon and found may colorful maples: red, yellow and orange.

(photo by Kate St. John)

Anatomy: Sternum

I thought my blog’s anatomy series was nearly over because I was running out of material.  Then last night Chuck Tague presented an excellent program at the Wissahickon Nature Club on how bird anatomy is adapted for flight.  Now I’m inspired.

What most impressed me is that birds have the same basic internal equipment that we do — lungs, backbone, arms, toes, etc. — but the location, proportions and shapes of their body parts are altered because they fly.

For instance, human heads can afford to be heavy (and they are!) because we walk upright and easily balance our heads at the top of our bodies.  Birds’ heads cannot be heavy unless something equally heavy balances them horizontally at the other end.  Their solution is to have lightweight heads and alter the shape of their bodies to change the weight distribution.

Which leads me to the keeled sternum or breastbone.  It provides the anchor for the flight muscles.  Notice that it’s huge and sticks out!  When a bird flies its keel is positioned in the air the same way a boat’s keel is positioned in the water — one of many reasons why the sternum takes this shape.

If humans had keeled breastbones we’d tip over as we walk.  Instead our sternum is flat and positioned vertically.

There are a few birds who don’t have keeled breastbones and they are…  can you guess?… birds that don’t fly.  Ostriches, emus, cassowaries, rheas and kiwis all have flat sternums.  A keel would get in their way and possibly throw them off balance as they walk.  Their unusual sternum (for a bird) gave their group a name.  Ratites means “raft-like sternum.”

(photo from Wikimedia Commons.  Click on the photo to see the original.)