Archive for August, 2012

Aug 11 2012


Published by under Schenley Park,Trees

This week I found a bumper crop of haws littering the sidewalks in Schenley Park.

Haws are the fruit of hawthorn trees:  short trees with low branches, tangled twigs and long, thin, leafless thorns (1"-2" long).  The thorns are a great clue for identifying the tree.  Haw+thorn.

Hawthorn fruits look like small apples or rose hips, all members of the rose family.  They're a favorite food of robins and cedar waxwings, and people sometimes preserve or ferment them into jam, jelly, snacks and beverages.  The trees occur worldwide in the northern hemisphere so there are many recipes.

Hawthorn trees are really easy to identify as a genus (Crataegus) but difficult as a species because they hybridize and speciate so often.  At one point botanists listed more than 1,100 species in North America but they've since clumped them down to about 100.

The Sibley Guide to Trees says hawthorn species are so similar that identifying them is best left to experts.  However, armed with rudimentary knowledge and my Sibley guide, I'll go out on a limb for these Schenley trees.

My guess is that they're a variant of Downy Hawthorn (Crataegus mollis) because the haws are ripening in August and the ripe ones soon fall to the ground.

(photo by Kate St. John)

2 responses so far

Aug 10 2012

Taking A Dip

We've all seen robins splashing in water but how many of us have seen a hawk take a bath?

Last Saturday it was already hot when Gregg Diskin took a walk through Schenley Park with his camera.  Near Bartlett Playground he saw a hawk disappear under the bridge so he walked down the path to investigate.  There he found an immature red-tailed hawk taking a dip in the stream.

Bathing is a relatively vulnerable activity so we rarely see adult hawks doing it.  My hunch is that this bird was one of the two immature red-tails who starred in Monday's blog.  He had almost no fear of people, felt right at home, and continued to bathe while Gregg snapped a series of pictures.

Click on the photo above for a slideshow of the red-tail's bath.  At the end he has something to say to Gregg.

(photos by Gregg Diskin)

2 responses so far

Aug 09 2012

Gotta Fishy! Gotta Fishy!

Last weekend we spent four days at Cape Cod where I had the opportunity to see piping plovers and least terns, two birds that are extremely rare in southwestern Pennsylvania.

Both species are endangered because they nest on the ground on sandy beaches, the same places where humans like to own property and spend their vacations.  At the Cape, nesting areas are roped off above the water line and dogs are prohibited off leash (or prohibited altogether).

During our stay people and birds coexisted peacefully.  Some people, like me, were fascinated by the birds.

At Ridgevale Beach the least terns were numerous and vocal at low tide.  Several immature terns were still being fed by their parents even though they could fly.  The youngsters waited on the sand, immobile and camouflaged, while mom and dad hunted for food.

Their parents flew over the water looking for finger-length silver fishes.  Sometimes they hovered above, waiting for the perfect moment to dive and snag a fish.

Zip!  As soon as a tern plucked a fish out of the waves he flew around the area giving a loud, continuous, 4-note call, "Gotta fishy! Gotta fishy!  Gotta fishy!"

Eventually he flew back to land with a flourish of upraised wings and present the fish to his youngster.  Sometimes the youngster just blinked and looked away.  He wasn't hungry!   The fish were that plentiful last weekend.

When the colony found a big school of fish they were all in the air, flying swiftly, carrying fish, calling "Gotta fishy, gotta fishy, gotta fishy."

Their voices carried so far that I often heard least terns before I reached the beach.

(photo by Steve Gosser)

2 responses so far

Aug 08 2012

The Prevailing Wind

Published by under Weather & Sky

Except during storms, Pittsburgh is not a very windy place.  This is especially true in July and August when our average wind speed drops to 9 mph and is usually from the west.

The direction of the "usual" wind is called the prevailing wind and it shapes our weather, rainfall, landscape and vegetation.

In places where the wind is strong the prevailing wind can be seen even when it isn't blowing.  Witness the trees in the photo above at Cardigan Bay in Wales.

On a global basis the prevailing wind is influenced by the earth's rotation.  As the earth spins the atmosphere swirls in a consistent way:

  • From the equator (0o) to latitude 30o north and 30o south the prevailing winds are from the east.  These are the trade winds that brought Christopher Columbus and cattle egrets(*) to the New World.
  • From latitudes 30o to 60o the prevailing wind is from the west.  The westerlies returned the trading ships to Europe.
  • From latitudes 60o to the poles the prevailing wind is again from the east.

At any given point on earth the prevailing wind might not obey these rules due to location at a border latitude (30o, 60o), topography, or seasonal change.

Pittsburgh, at 40oNorth, has no stark topography so our prevailing wind obeys the general rule:  it's from the west or WSW.

We can see this on a wind rose that plots wind direction over time. Each data point is placed at its compass position.  The more data points from that position, the longer the ray from the center.

Here's a Pittsburgh wind rose from EPA showing our daytime wind for the seven months of ozone season (April 1 to October 31).


Click here to see a wind rose depicting 30 years of data on Pittsburgh's wind direction and here for the wind roses of 11 secondary airports (smaller towns) in Pennsylvania.

And what's the wind like for those trees in the photo above?  Right now it looks like this (scroll down to see the label "Cardigan Golf Club" and watch the wind swirl around the UK).


(photo of wind-shaped trees by Rudi Winter from Wikimedia Commons. Wind rose from Click on the images to see the originals.)

* Cattle egrets are originally from Africa.  They flew to South American on their own -- perhaps in a strong storm carried by the trade winds.

3 responses so far

Aug 07 2012

Potato Chip

Have you seen a female goldfinch lately?

Female goldfinches disappear during most of July to spend 95% of their time on the nest.  They don't even stop incubating to eat.  Their mates feed them at the nest by regurgitation.

To do this the male goldfinch (above) stores seeds in his crop, then flies in a big, undulating circle above his nesting territory, all the while singing "Potato chip, Potato chip."

If his lady is hungry she calls softly to him from the nest, "teeteeteeteeteetee" and he flies down to feed her.

After the eggs hatch, the female broods them for four days.  And then, at last, she's off the nest to help her mate feed the babies. Soon the fledglings will be at the feeders, too.

If you heard the "Potato chip" song above your yard in July, watch for goldfinch fledglings in August.

(photo by Chuck Tague)

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Aug 06 2012

Whatcha Got There?

This spring two red-tailed hawk babies fledged from the Panther Hollow Bridge in Schenley Park.  They're already as big as their parents but they don't act grown up.  They're not wary of humans and they whine when they're hungry.

At this stage they're learning how to capture and kill prey with their feet.  They've been watching their parents for tips but they always hope their parents will deliver dinner.  Meanwhile the adults are waiting longer to feed them, hoping the kids will take the hint: "Feed yourself!"

The two juveniles are often found together because Little Brother, the younger of the two, follows his big sister at meal times in case she catches something.

In mid-July Jim Funderburgh found the two hawks exploring the park on their own. Little Brother whined but his sister had nothing to give him so he found a mouse-size object and practiced his prey techniques.

In the video he clutches to kill it ... but it surprises him.  Yikes!


Whatcha got there, Little Brother?

A pinecone!

(photo and video by Jim Funderburgh)

2 responses so far

Aug 05 2012

Slightly Aggravating

Published by under Plants

When I visited Jennings Prairie a week ago it took me a while to remember the name of this plant.

The flower spike is interesting but the flowers are unspectacular: small, five-petaled, yellow.

However, the leaves stand out because they're so odd with small leaflets wedged between larger ones on the stem.

By examining the leaves I remembered this plant is slightly aggravating.  When it goes to seed the pods have burs that stick to your clothing.

The seeds are "aggravating" and that sounds almost like "agrimony."

Small flowered agrimony.

I wish I had a mnemonic for the leaves.

(photos by Kate St. John)

One response so far

Aug 04 2012

Green, But Not A Hummer

Yes, he's green but he isn't a hummingbird.

If you follow Chuck Tague on Facebook, you saw his comment when he posted this photo last year on June 29, 2011:

"Leapin' Lizard (with a sweet tooth). I caught this Carolina Anole, "Anolis carolinensis", licking sugar water from a hummingbird feeder near Hontoon Island, Volusia County, FL. This is the first time I saw anoles eat anything but small invertebrates."

A quick glance at the hummingbird feeder might not have revealed that this isn't a ruby-throat.

Expect the unexpected in Florida.

(photo by Chuck Tague)

2 responses so far

Aug 03 2012

Peaceful Birding

Today's video is a beautiful, peaceful, bird watching experience by local photographer Bob Greene, Jr.

Originally created for the Three Rivers Birding Club's 2012 Slide Slam, Bob's 12.5 minute video cameos the behavior of 35 species accompanied by music from the Celestial Aeon Project.

All of the birds are gorgeous.  My favorites are the nest-building house wren and the leaping greater yellowlegs.  See if you agree.

Sit back, relax, and enjoy watching birds at your desk.

(video by Bobby Greene)


6 responses so far

Aug 02 2012

Dark Monarchs Fly Better

Here's something I would never have known had I not read it in Science Daily.

Did you know that the migratory generation of monarch butterflies -- the ones that fly to Mexico -- are darker red than the earlier, more sedentary generations?  The monarchs you're seeing right now are less red than the ones you'll see in late August.

You're probably aware of this color difference if you raise and tag monarchs as Marcy Cunkelman does, but do you know why the last generation is darker?  Scientists are on the verge of finding out.

According to Science Daily and PLoS ONE:  Recent research, led by Andrew Davis of the University of Georgia, tested 121 captive monarchs in an apparatus called a tethered flight mill where they quantified butterfly flight speed, duration, and distance.  They found that monarchs with darker orange wings overall flew longer distances than those with lighter wings.  This suggested that pigment deposition during metamorphosis is linked with flight skill traits such as thorax muscle size, energy storage or metabolism.

It makes sense to me that a bug that has to fly to Mexico is born with the traits necessary to do the job, and it's not too amazing that dark color is one of them.  In birds, dark feathers are stronger than light-colored feathers.  Perhaps this applies to the wing scales of butterflies, too.

For a picture of these color differences, see the Science Daily article here and the original article at PLoS ONE.

Meanwhile, if you have a butterfly net and a camera you can do some research on your own.  Look for monarchs now and again at the end of the month. When your photographs record darker red monarchs in late August, you'll know why.

(photo of a monarch butterfly by Marcy Cunkelman)

2 responses so far

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