Monthly Archives: November 2012

Form, Function, and a Quiz

All birds have feathers, wings and two legs but they certainly don’t look alike, not even in silhouette.

Birds in the same family can look very different.  Take sandpipers (Scolopacidae) for instance:

  • Sanderlings are small sandpipers with short legs and a short pointy bill.
  • Whimbrels are more than twice the sanderlings’ size with relatively short legs and a long down-curved bill.
  • The critically endangered spoon-billed sandpiper is smallest of all with short legs and a spoon-tipped bill.

Why are they so different?  Their features have evolved to match their lifestyles.

  • Sanderlings chase waves to catch invertebrates tossed on sandy beaches.  They need to be quick so it’s important to be close to the ground and able to pick up prey quickly.
  • Whimbrels use their long curved bills to probe the mud of salt marshes and tidal flats to find crabs and invertebrates.
  • Spoon-billed sandpipers sweep their bills side to side in shallow water to capture prey.  Like the roseate spoonbill their lifestyle has shaped their bills.

In architecture, form follows function.  In birds their form happened first, then the birds with better features survived.


And now for a Quiz!

Every time I look at the silhouettes, I find myself trying to identify the birds.  There are 26 individuals and 3 flocks in the image.  How many of the silhouettes can you identify?

Tips:  I’ve numbered the individuals and marked the flocks with letters below. Assume each flock is made up of the same species.  Some of the 26 individuals are repeats.  If you can’t identify the exact species, name the bird by group, as in “gull.”

Post your answers in the comments.  Good luck!

(Inspiration for this Tenth Page is from page 10 of Ornithology by Frank B. Gill.  Bird silhouettes from Click on the image to see the original)

How Does An Owl Hide?

Great Gray Owl Avoidance Behavior from Sparky Stensaas on Vimeo.

Great gray owls (Strix nebulosa) live in coniferous forests and taiga of the North.  Their year-round range extends into upper Minnesota where this one was filmed in March.

In the video you’ll see two clips of the owl avoiding detection by two other species: a bald eagle and a raven.

It’s hard to imagine a large owl being afraid of anything, but he’s actually 15% smaller than a great horned owl.  He appears large because of his fluffy feathers.

In March he has a special reason for remaining hidden.  His nest is probably nearby.

Watch how the owl “gets skinny” to avoid being seen.

(Click here for more information on this video by Sparky Stensaas, Photonaturalist>)

Why Not Here?

When I travel east on the Pennsylvania Turnpike I’m always amazed when I reach Bedford County and see the landscape dotted with trees like this one.  They grow like weeds east of the Alleghenies, but not in western Pennsylvania.

When I saw them last weekend I said to myself, “Cedars.  Why don’t we have cedars at home?” and I set myself to find out.

My first surprise was that this tree is not a cedar at all.  It’s in the cypress family and it’s a juniper (Juniperus virginiana) whose common name, Eastern Redcedar, is probably a reference to its aromatic wood.

The second surprise — for those of us who live outside their range — is that junipers are very hardy and grow under a wide variety of conditions.  They’re pioneers in disturbed or damaged soil, especially in old fields and along roadsides, and they live a long time — up to 850 years.

To identify a juniper, look for a small evergreen with reddish-brown bark that peels off in strips.  The young trees have sharp needle-like leaves, the mature ones have scale-like leaves.  (This is hard to describe; see picture below).

The juniper’s aromatic wood is used to line cedar chests and keep moths away.  Its bluish waxy-looking berries are a favorite food of many mammals and birds, especially cedar waxwings, eastern bluebirds and wild turkeys.  People like the berries too.  We use those of Juniperus communis to flavor gin.


The first picture is what junipers look like near the turnpike in Bedford County, shaped like lollipops because they’re browsed by the overabundant deer. The picture below shows their normal shape when the deer population is in balance. I suppose we could use junipers as a deer population gauge… but they don’t grow here in Pittsburgh.


Junipers grow wild in the far southwest corner of Pennsylvania, in Ohio, West Virginia, Maryland, the Appalachians, and eastern Pennsylvania.  They grow from southern Maine to Georgia, from Delaware to Kansas (see map).  Why not on the Pittsburgh and Allegheny Plateaus?

I haven’t found the answer.  It’s still a mystery.


(photo credits:  Deer-browsed juniper by Paul Bolstad, University of Minnesota,  Juniper berries by D.E.Herman, USDA. Eastern juniper at Sandy Hook, NJ by Miguel Vieira on Wikimedia Commons. Click on the photos to see the originals.)

Two Levels Of Distortion

Earlier this month I watched a flock of robins and starlings feast on the Bradford pears near Heinz Chapel.  Birds usually don’t sing in the fall but this flock was muttering and whisper-singing.  Three birds in particular caught my ear.

A robin sang softly.
A starling mimicked the robin.
A mockingbird mimicked the starling mimicking the robin.

By the time the robin’s song came out of the mockingbird’s mouth it was nearly unrecognizable.   (Click here for the robin’s song.)

European starlings, on the left above, are considered mimics but they have wiry voices that distort whatever they say.  Here’s a typical starling song. At the 00:23 mark he does a good imitation of a house sparrow. I couldn’t find an audio clip of a starling mimicking a robin.

Northern mockingbirds, on the right, are much better mimics than starlings.  They can follow a robin’s tune and cadence but miss the melodious thrush harmony.  They brazenly mask this deficiency: “I meant to sing the tune without the harmony.”  Click here to hear a mockingbird mimicking many birds, including robins.

The mockingbird at Heinz Chapel clearly copied the starling’s wiry song including his poor imitation of the robin.

It was like a game of telephone.  There were two levels of distortion.

(European starling by Paul Carter via Wikimedia Commons. Northern mockingbird by Dick Daniels via Wikimedia Commons. Click on these imbedded links to see the original photos.)

The Triple Divide

There’s a unique place in north central Pennsylvania at the top of three major watersheds. It’s called The Triple Divide.

When a raindrop falls there it can split three ways:

  1. In one direction, it flows west to the Allegheny River, down the Mississippi watershed and into the Gulf of Mexico.
  2. Or it flows north to the Genesee River, Lake Ontario, the Saint Lawrence watershed and into the north Atlantic.
  3. Or it flows southeast to Pine Creek, the Susquehanna River, Chesapeake Bay and the Atlantic Ocean.

The spot is in Ulysses Twp, Potter County, Pennsylvania and is marked with the sign pictured above.

The location itself is unremarkable.  It’s not a big mountain, just a hill on the Allegheny Plateau near the New York state line.  It’s not even the highest point in Pennsylvania, but it spawns three major North American rivers:  the Mississippi, the St. Lawrence and the Susquehanna.

According to Dr. Robert N. Andersen at University of Wisconsin Eau Claire, “Triple divide points are ubiquitous in North America. Wherever there is a confluence of two streams there is a Triple Divide Point uniquely associated with the confluence. ”  Then he uses Pittsburgh’s confluence of the Allegheny and Monongahela Rivers to describe how to find a triple divide near us.

Beginning at the Point in Pittsburgh, trace the border of the Allegheny and Monongahela watersheds, moving upstream. Eventually you reach the place where the border ends.  At that point in Somerset County, east of Berlin, PA, is a triple divide that drains the Mississippi (via the Conemaugh and Youghiogeny), the North Branch of the Potomac, and the Susquehanna River (via the Juniata).

In the western U.S. there are triple divides that drain to both the Atlantic and Pacific.  And somewhere in Canada there’s an oceanic triple divide where a raindrop can split and flow to the Arctic, the Atlantic and the Pacific Oceans.

Follow a raindrop uphill and you’ll eventually find a triple divide.

(photo by Nicholas A. Tonelli on Wikimedia Commons. Click on the image to see the original and explore the location on Google Maps)

Occasional Fisher

Belted kingfishers don’t nest in Schenley Park but they do visit during migration.  Panther Hollow stream and lake are their favorite haunts.

Visiting kingfishers shuttle up and down the valley to find favorable fishing spots.  They perch above the man-made lake and stare at the cloudy water.  The fish are hard to see.  If they don’t catch a meal at the lake the birds head down Junction Hollow to the Monongahela River.

Junction Hollow must be amazing to kingfishers because it’s a waterless valley.  Four Mile Run was there but it’s buried beneath the playing fields and bike trail.  Those amenities are making the best of an unnatural situation.

The Run was buried long ago but any hope of daylighting it was dashed in 1989 when Sol Gross bought 28 acres of Junction Hollow and further buried the valley under construction debris generated by his demolition company.  The City stopped his dumping and everyone ended up in court, but the damage was done.  The creek is so far underground now that it’s way too expensive to remove the debris.  Hence the fields.

Kingfishers come and go through Schenley Park in the fall.  Gregory Diskin found this female at the lake on September 30, then saw none until last week.

When the lake freezes this bird will leave for a site with open water.  Until then, keep your ears open for the rattling call of an occasional fisher.

(photo by Gregory Diskin)


p.s.  Want to see a kingfisher soon?  Check Duck Hollow where Nine Mile Run empties into the Monongahela River.

Winter Visitor

Autumn brings a change in bird distribution.

Broad-winged hawks, osprey and most of the turkey vultures leave for the south but we gain at least three resident raptors:

  • Northern goshawks hang out in Pennsylvania’s forests (in small numbers).
  • Merlins visit southwestern Pennsylvania and sometimes the City of Pittsburgh.
  • In the Pymatuning area you’re likely to find rough-legged hawks.

Don Weiss photographed this dark-morph rough-legged hawk at Miller’s pond in Crawford County last weekend.  In winter it’s a reliable place to find this typically northern bird.

(photo by Don Weiss)

How Birds Improved Upon Their Past

Last week I wrote about the Urvogel Feather of Archaeopteryx lithographica, the oldest feather ever found.  Now that I’m beginning the Tenth Page series I’ve discovered that page 30 of Ornithology has a neat comparison of Archy’s skeleton to that of modern birds.

Archaeopteryx lithographica is recognized as a link between dinosaurs and birds because he has features of both.  Like dinosaurs he has**:

  • jaws with sharp teeth
  • three fingers with claws
  • a long bony tail
  • hyperextensible second toes that are “killing claws”
  • feathers, which also suggest homeothermy (This characteristic is rather self-fulfilling in that dinos were not thought to have feathers until Archy was discovered.)
  • and various dinosaur skeletal features.

Like birds he has:

  • flight feathers, the asymmetrical feathers on his wings
  • broad wings
  • hollow bones
  • a furcula, the “wishbone”
  • and reduced fingers.

But as a bird he’s not quite there yet.  Modern birds have skeletal adaptations that make flight much easier than it must have been for Archy.  This is evident in a skeletal comparison.

Page 30 of Ornithology describes how modern birds improved on Archaeopteryx lithographica’s features:

  1. Skull: In modern birds the braincase is expanded and the bones are fused.
  2. Hands: Most of the bones are fused
  3. Pelvis: Bones are fused to make a sturdier structure
  4. Tail: Bones are fused, the tail is shorter
  5. Sternum: Expanded to a large keel for attaching the flight muscles
  6. Rib cage: Has cross-struts (“horizontal uncinate processes”) for strength.

So, if you have a lot of time to improve your flight abilities — say 150 million years — this is what you get.

Inspiration for this Tenth Page is from page 30 of Ornithology by Frank B. Gill.

** The dino list is quoted from the Wikipedia article on Archaeopteryx.
Photo of Archaeopteryx lithographica, Solenhofener specimen from Wikimedia Commons.  Skeleton of modern bird from Illustrations of Zoology by W. Ramsay Smith and J S Newell, in the public domain via Wikimedia Commons, red annotations added by Kate St. John.  Click on the images to see the originals.

Thirty Turkeys

Sometimes, if you’re lucky, you can see a whole flock of turkeys on the move.

In this photo Steve Gosser found 30 of them at Beaver Run Reservoir in 2010.  This fall I saw 16 at Schenley Park.

If you’re quiet you might also hear them calling or gobbling.  Click here and scroll down to hear an assortment of turkey sounds from purrs to explosive gobbles.

Happy Thanksgiving.

(photo by Steve Gosser)

Why So Many Robins?

Why are there so many robins in Pittsburgh right now?  Food.

What are they eating?  You’re looking at it.

These are Bradford callery pears, the fruit of a popular small street tree that has pretty white flowers in early spring.

This particular cluster is from a row of trees next to the Pittsburgh Board of Education on Bellefield Avenue but I’ve found Bradford pears at Carnegie Mellon, at Pitt, on neighborhood streets, in mall parking lots … they’re everywhere.

And they’re imported. Callery pears are normally thorny trees.  Native to China they were first brought to the U.S. in 1918 as an experiment in producing rootstock for pear orchards, but that didn’t work out.  Instead, one of the experimental trees grew without thorns, was recognized for its ornamental value and became the “Bradford” cultivar.  By 1982 Bradford callery pears were the second most popular landscape tree in the U.S.

As usual with non-natives, they are easy to point out in late November because they still retain their leaves.  Before they fall the leaves turn yellow, orange and then deep red, another reason for the tree’s ornamental value.  In spring the flowers bloom earlier than our native trees.  (I happen to think the flowers smell bad but most people don’t notice it.)

Since their introduction, callery pears have become naturalized and in some places invasive.  It’s easy to see how their seeds spread when you watch a flock of birds feasting on them.  This year the fruit is especially prolific and so are the robins and starlings.

As soon as the fruit is gone and the ground is covered with snow, the robins will go.  Until then, it’s a party.

(photo by Kate St. John)