Archive for September, 2011

Sep 30 2011

Broad-winged Spectacle

According to migration statistics from Hawkcount.org, the bulk of broad-winged hawk migration passed through Pennsylvania in mid-September with one last pulse last Tuesday.

Most of them followed Kittatinny Ridge, the easternmost spine of the Appalachian Mountains where Hawk Mountain Sanctuary is located.  Here are the three highest broad-winged counts at Hawk Mountain this month:

  • Sept 13 — 1,572
  • Sept 17 — 2,813
  • Sept 19 — 1,701

You might think this means that hawks travel in flocks but they don’t.  Instead they watch each other for flight cues.  If one hawk finds a thermal with good lift, others fly over and rise on it as well.  Soon they form a “kettle” of hawks stirring round and round in the rising air.  As each one  reaches sufficient altitude it sets its wings and glides southward to find the next thermal.

After the broad-wings leave Pennsylvania they make their way to the Texas Gulf Coast and follow the eastern edge of the Gulf of Mexico on their way to their wintering grounds in South America.  By the time they pass Veracruz, Mexico, all the broad-wings of North America are concentrated in a narrow corridor.  Their numbers at Veracruz are astonishing, as shown in their three highest counts this month and in the video above.

  • Sept 23 — 136,376
  • Sept 24 — 128,272
  • Sept 22 —  68,724

I tried to imagine 136,000 hawks in my Pittsburgh neighborhood and my first thought was, “There isn’t enough food here for 136,000 hawks!”  But there is — for a short time — in Veracruz.

Broad-winged hawks eat small mammals, reptiles, amphibians, large insects and songbirds.  Right now they’re traveling with millions of dragonflies and songbirds who are also on migration.

That’s why they migrate in September.  That’s why there’s a spectacle of broad-winged hawks.

(video from Veracruz Hawkwatch on YouTube)

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Sep 29 2011

Camouflage

Published by under Quiz

There’s a leopard in this tree.

Do you see it?

If you’re stumped here’s a digital closeup, but where is that in the tree?

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I wouldn’t have been able to find the leopard without the annotated photo (see below).   

I’m glad there are no leopards in Pennsylvania’s woods!

(photo taken in Tanzania by Nevit Dilmen via Wikimedia Commons.  To find the leopard, click on the image and move your mouse over the original photo which has a yellow box around the leopard.)

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Sep 28 2011

White Snakeroot

Published by under Plants,Schenley Park


Composite flowers are putting on their last big show.  Goldenrods, asters and white snakeroot are blooming everywhere in the weeks before first frost.  They’re easy to find in Schenley Park.

White snakeroot (Ageratina altissima, formerly Eupatorium rugosum) has white umbels that resemble Boneset (Eupatorium perfoliatum) but the leaves are much different.  Instead of large perfoliate leaves white snakeroot has smaller leaves with stems.

Use a magnifying glass on the flowers and you’ll see Y-shaped stamens poking up from the tiny five-pointed flower cups.

…”The better to pollinate, my dear.”

Read the story of this plant — and who it killed — on the Flora Pittsburghensis blog, the source of this photograph.

(photo by Christopher Bailey on Flora Pittsburghensis)

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Sep 27 2011

Spring Tide Tomorrow

Published by under Water and Shore


I live in a land-locked place where we can safely disregard the activities of the ocean but if I lived in coastal Maine, and especially if I owned a boat, I’d better know there will be a spring tide tomorrow.

A “spring tide” in the fall?

Yes.  A spring tide is the highest high tide and it’s followed by the lowest low.  The name has nothing do to with the season but rather that the water is “springing up.” 

Tomorrow at Bar Harbor there will be a spring tide of 13.2 feet at 11:40am because of two things the moon is doing today. 

Everyone knows the moon affects the tides but we tend to forget that the sun does too.  This morning we had a New Moon (all dark) at 7:09am.  New Moons occur when the moon is between the earth and sun — all three in a row, an alignment called syzygy(*).  With the moon and sun both pulling at the same side of the earth the high tides are that much higher. 

Tonight at 9:10pm the moon will be at perigee, its closest approach to the earth.  In this position it pulls the ocean more than usual and makes the high tide higher.

Near syzygy and moon perigee are nothing unusual but when they occur at the same time the perigean spring tide is very high.  This month the two events are 13 hours apart so the spring tide will be high but moderated. 

And for whatever reason, it’s delayed until tomorrow in Frenchman’s Bay.  

(photo of waves at Acadia National Park in Maine, from Shutterstock.com.)

(*)  See the comments for more information.  Astronomers, I look forward to your feedback on these definitions!

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Sep 26 2011

Last Gasp of Dying Ashes

Published by under Schenley Park,Trees


If you live in the Pittsburgh area, now is the time to see it.  Our ashes are dying.

Since 2007 when emerald ash borer was found in Cranberry, I’ve known our ash trees were doomed by this insect pest but their death is occurring faster than I expected.

In May 2010 I noticed emerald ash borer in Schenley Park.  At that time only one tree was noticeably affected with branch dieback, bark holes and woodpecker damage.

Now only 16 months later nearly all the ashes in Schenley Park are visibly infected and dying.  Only the few being treated with insecticide by the Pittsburgh Parks Conservancy have any chance at survival.

Trees under stress lose their leaves early and that’s exactly what’s happening.  Throughout Schenley Park the ash leaves haven’t even bothered to change color.  They just fall off.  There are usually tufts remaining near the top to show the tree isn’t dead yet.  That’s what you see in my photo above.

In this brief period before the other trees drop their leaves, the dying ashes stand out.  You can see them in local woodlands and along the road.  One such place is a stand of young, dying ash trees on the east side of I-79 just south of the Wexford exit.

Watch for leafless trees with opposite branches and stout twigs.  It’s the last gasp of our dying ash trees.  By next year they’ll be dead.

(photo by Kate St. John)

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Sep 25 2011

Monarchs on the Move


Every year at this time I blog about monarch butterfly migration. I hope you don’t tire of it.  It’s just so amazing to me that this butterfly migrates as much as 2,500 miles to spend the winter in Mexico — and we can see it happening.

Years ago people suspected the butterflies were migrating but didn’t know where they went.  After 40 years of tagging and tracking monarchs, Dr. Fred Urquhart found their wintering site in 1976 in the mountains of Mexico.  At first the locations were kept secret because there are so few of them, but nowadays they are eco-tourist destinations where visitors can observe millions of monarchs in the Oyamel fir trees.

Right now the butterflies are on their way.  Yesterday afternoon at the Waterfront Shopping Center I was loading my car when I saw a monarch fly by.  I paused and looked up and counted 10 monarch butterflies flying southwest over the parking lot.  The wind was calm, the air was warm and all of them were fluttering in the exact same direction, each bug on its own long journey.  Wow!

Monarchs are on the move across the country.  You can watch their progress on the Journey North website or in your own neighborhood.  In southwestern Pennsylvania you can know a monarch butterfly is migrating by these three things:

  1. It’s the right time of year —  September is prime time.
  2. The butterfly is fluttering or gliding in one direction without pausing to eat.
  3. It’s flying southwest.  

It’s easy to see them.  Keep looking up.

(photo by Marcy Cunkelman)

p.s.  This monarch is male.  You can tell because he has dots on his hind wings.  The females don’t have them.

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Sep 24 2011

A Pattern Found in Nature

Published by under Beyond Bounds,Plants

Though this looks like artistic velvet flocking, it’s actually a closeup of a flower.

Persian carpet flower (Edithcolea grandis) is a desert plant from East Africa named for Miss Edith Cole (1859-1940) who found it in British Somaliland during a plant collecting expedition in 1895.  It’s the only plant in its genus.

When you step back from the flocking, it looks like this:

Very beautiful.  No wonder people plant it in desert gardens.

(both photos by Frank Vincenz from Wikimedia Commons.  Click on each photo to see its original.)

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Sep 23 2011

Fly With A Bird

Published by under Birds of Prey

Very cool video of a falconer from ParaHawk USA flying with his Harris’ hawk in San Diego County, California.

Awesome!!

See ParaHawkUSA.com for more information.

(video from ParaHawkUSA via YouTube)

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Sep 22 2011

Cucumber of the Woods

Published by under Trees

While hiking last Sunday I found this leaf and two fruit pods at Moraine State Park.  I walked past them three times before I paused to marvel at their size and color — and then I picked them up.

The leaf is nine inches long, larger than my outstretched hand.  The seed pods are lumpy with bright red-orange seeds.  The one on the right has ripened to a waxy rose-pink.  The lefthand pod is overripe.  Its skin is drying and the seeds are falling off.

These specimens fell from a Cucumbertree, also known as a Cucumber Magnolia (Magnolia acuminata), the most winter hardy of all magnolias.  It grows wild all the way to Canada but is found only as a single tree here and there in the woods.  In the spring its flowers are two inches long and green, not showy.  After pollination they form dark green seed pods that look like cucumbers and gave the tree its name.

I’ve never seen the “cucumbers.”  They’re always at the top of the tree.  What I do see are their ripened forms which would have stayed in the canopy but for the work of chipmunks and squirrels.

Last Sunday the squirrels and chipmunks were climbing trees and biting off the stems of fruits and nuts, letting them drop to the forest floor to be gathered later.  My hike was punctuated by a random rain of acorns, hickory nuts and these large heavy fruits.  I was lucky I wasn’t hit.

Instead I’ve left behind a disappointed squirrel whose food I collected from the North Country Trail.

(photo by Kate St. John)

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Sep 21 2011

Flying Snails

Published by under Water and Shore

We’re all familiar with plants whose seeds have hooks that cling to fur and clothing.  In this way the seeds travel miles from their parent plant to germinate in a new place.

Last week in surprising news we learned that snails may be able to do the same thing by clinging to birds.

Scientists from the Smithsonian Tropical Research Institute studied the DNA of two sister species of horn snails, one from the Atlantic, one from the Pacific.

Millennia ago these tiny snails were the same species because the waters of the Atlantic and Pacific were joined by an opening where Central America is today.  Three million years ago the land rose up at Panama, the oceans were divided, and the snails eventually became two separate species.

Scientists expected to find that the two had not intermingled since then, but DNA evidence showed that the Pacific snails had bred in the Atlantic one million years ago and the Atlantic snails had done the reverse 70,000 years ago.

How?

The theory is that the snails flew.  They were either ingested by a shorebird and lived in the gut long enough for the bird to fly across Panama and excrete them in the other ocean(*), or they traveled in the mud clinging to a bird’s feathers or feet.

I don’t know about the first theory but the second is quite plausible, especially if the snails were small. 

In the 1800’s Charles Darwin showed that birds helped plants colonize the Galapagos when he collected a ball of mud from a bird’s plumage and raised 82 plants of five species.  If plants travel in the mud, why not tiny snails?

Here’s a buff-breasted sandpiper to show how it’s done. 

Buff-breasted sandpipers nest in the Arctic tundra and winter in Argentina.  During their long migration they stop to feed on muddy shores in North and South America where they inevitably get dirty.

Look at this bird’s feet.  Mud!

What’s in that mud?  Maybe seeds, maybe microscopic snails…

So my question for this bird is:  Who’s traveling with you?

(photo by Steve Gosser)

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(*) Panama is about 37 miles wide at its narrowest point.

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