Yearly Archives: 2012

Winter Trees: Black Cherry

Schenley Park, Trees, Winter Weeds & Trees

Today’s tree is easy to identify all year simply by looking at its bark.

Black cherry (Prunus serotina) is a medium to large tree, 50 to 100 feet tall.  Mature trees have dark colored bark that looks like burnt potato chips.  The shadowy photo above accentuates the chips.

In bright light the trunk looks paler but the chips are still there, as you can see by this photo taken in full sun.

 

Young trees have smooth shiny bark with pale horizontal lines or lenticels.  Even the twigs have lenticels that appear as spots in the picture below.  The buds are alternate, small and scaled.  This twig looks like it wants to open its buds, proof that it’s been a weird warm winter.

 

Black cherries are a favorite of birds in late summer because the trees produce an abundance of small red to purple cherries, 1/3″ in diameter.  Foresters like the tree for it’s cherry-colored wood which fetches a good price.

Keep your eyes open for black cherry trees and you’ll be surprised how many you find.

(photos by Kate St. John)

Full Moon, Let’s Talk

Bird Behavior, Birds of Prey

Do owls hoot more when the moon is full?

Eurasian eagle owls do.  Maybe great horned owls do too.

In 2009 biologists conducted a study in Spain to find out if moonlight influenced Eurasian eagle owl vocalizations. They radio-tagged 26 breeding eagle owls and tracked them continuously during all phases of the moon.

When the scientists analyzed the data they found that the amount of hooting was directly correlated to the amount of moonlight.  On new moon nights the owls hardly hooted, but as the moon got brighter they had more to say and they said it from higher perches where their white throat patches gleamed in the moonlight as they spoke.

The white throat patch is important.

Like our great horned owls (Bubo virginianus), Eurasian eagle owls (Bubo bubo) have white throat feathers that are only visible when they hoot.  (The owl in this picture is hooting even though we can’t hear him.)  In bright moonlight the white throat patch is apparently a visual cue that backs up the sound.  Perhaps it helps the mate or rival find the bird that’s vocalizing.

Tonight the moon is full.   Will our great horned owls be talking?   Listen…

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

New Guide to Petrels, Albatrosses and Storm-Petrels

Books & Events, Water and Shore

For humans the sea is the last frontier, a place so foreign we think it’s uninhabited.  But it’s not.  The open ocean is home to millions of birds we never see on land:  petrels, albatrosses and storm-petrels.

Acclaimed ornithologist and author, Steve N. G. Howell, has written an excellent reference book about them, newly published by Princeton University Press. Petrels, Albatrosses & Storm-Petrels of North America describes in detail all the tubenoses (Procellariiformes) found off the coasts of North America.

Tubenoses earned their name because their nostrils are encased in tubes on top of their straight, hook-tipped beaks.  The structures help them smell their food, even in the dark, and excrete salt from the seawater they drink.  Tubenoses are excellent fliers and often make long migrations, sometimes circling an entire ocean in both hemispheres.

The book’s introduction helps us understand the sea and the birds who live there.  The oceans are mobile and full of currents, windy on the edges, windless in the middle with hotspots of abundance and places as barren as a desert.  The food supply can change in a day, in a season, and with storms.  The birds live on the wind.

The species descriptions are incredibly detailed with field identification, plumage and molt, distribution, and behavior.  Every account is richly illustrated with photographs of the birds and related or similar species.  The photographs are amazing, sharp and clear, even when there are towering waves in the background.  Quite a feat in a rocking boat!

The best tip in the book is one that has helped me on the few pelagic trips I’ve made in the Gulf of Maine.  Before you go out to sea, study the birds you’re likely to encounter (only 12 to 20 species on a day-trip, of which 4-10 will be tubenoses).  Early study really helps because it’s hard to juggle a field guide while observing birds on a windy boat.

Petrels, Albatrosses & Storm-Petrels of North America is a solid reference guide.  At 500 pages it weighs 4 pounds.  You might think this is too heavy to carry in the field — certainly it’s much more detailed than a field guide — but consider this.  To see these birds you must be on an ocean-going boat that has tables where you can set the book down and study it while you motor out to sea.

If you’re planning to see or study tubenoses you’ll want to own Petrels, Albatrosses & Storm-Petrels of North America by Steve N. G. Howell.  Click on the image above to read more about the book and buy it at Princeton University Press.

(book cover from Princeton University Press)

p.s. If you have the book in hand, check out my favorite photograph on page 66.

Pairing Up

Peregrines

I like February.  Not for its weather but because it’s the time when peregrine falcons begin to court and claim territory in Pennsylvania.

After months of inactivity peregrine pairs are hanging out together and making their claims quite obvious.  Last Friday Dorothy and E2 did this by perching at the highest point at the University of Pittsburgh’s Cathedral of Learning.  “This is ours!”

Yesterday Steve Gosser found a banded pair of peregrines at Presque Isle State Park’s Gull Point.  Though one of the falcons flew away, this one stayed close enough for Steve to get some great photos.

Gull Point is only 1.75 miles as the peregrine flies from downtown Erie where an urban pair would feel comfortable nesting, and not far from lakeshore bluffs if they prefer a pastoral setting.

I bet this Lake Erie pair is on territory.  Where will they nest?  Is anyone monitoring peregrines in Erie?

(photo by Steve Gosser)

Time To Wake Up

Mammals


It’s Groundhog Day all over again.

Moments ago (at 7:25am EST) Punxsutawney Phil emerged from hibernation, looked for his shadow, saw it(!) and told us we’ll have six more weeks of winter.  Amazing… considering how warm it’s been.

Every year Phil’s predictions are preceded by a week of partying and fireworks, and accompanied by much fanfare and ceremony.  Thousands attend the celebrations in person and by webcam.  It’s a formal occasion for Phil’s Inner Circle who wear bowties, top hats, greatcoats and gloves.

The gloves are useful.  Yes, it can be cold — it was 8 degrees in 2004 — but there’s a second reason.

Sometimes Phil is grumpy when he wakes up and it’s better for all concerned that he nip a glove instead of a hand.

I’m with ya, Phil.  I’m grumpy, too, before my first cup of coffee.

(photo of Punxsutawney Phil from the Groundhog Day website.  Click on the image to visit Phil’s website and read all about him.)

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p.s. No one had to wear gloves today.  Phil was not grumpy, but some folks in the crowd were quite grumpy about his prediction!

Winter Trees: Black Locust

Trees, Winter Weeds & Trees

A friend of mine from Maryland once remarked that Pittsburgh has ugly trees.  “The gnarled ones look like devil trees,” she said.

Though she didn’t know their name I think she was referring to black locusts whose winter profile can look spooky.

Black locusts (Robinia pseudoacacia) grow in twisted shapes if they’ve been broken, badly trimmed, or invaded by the locust borer that weakens and deforms the tree.  The tree pictured above has been through at least two of these assaults.

The bark on mature black locusts is gray-brown and so deeply furrowed it looks distressed. Though a bit spooky it’s a good field mark for identifying the tree.

 

Up close you can see that each bud is surrounded by paired thorns, like devil’s horns.

 

The thorns also grow on the trunks of young trees.

 

Black locust flowers are such good honey-sources that they’ve been planted for this purpose in Europe, Asia and southern Africa.  If you don’t live in the black locusts’ native range — the southern Appalachians from Pennsylvania to Georgia, and the Ozarks — you might think of them as devil trees where they’ve become invasive.

Black locusts thrive in old fields, disturbed woodlots and along roadsides because they tolerate pollution and poor soil.  They make their own fertilizer through a process called nitrogen fixation.  As members of the legume family, their roots have a symbiotic relationship with Rhizobium bacteria.  The bacteria enters the root hairs and the plant makes tumor-like growths to surround it.  This protects the bacteria which in turn takes in nitrogen and converts it to a form that fertilizes the plant.

With beautiful flowers and an ability to make fertilizer, they don’t deserve to be called devil trees.

(photos by Kate St. John)

In a Snow Year

Birds of Prey

January 20 – February 11 is the time for Pennsylvania’s Winter Raptor Survey (WRS) when volunteers drive prescribed routes and tally the number of raptors they see.

Many volunteers post their counts on PABIRDS where we learn that our most numerous winter raptors are red-tailed hawks.  (No surprise there!)

The reports include weather and snow cover conditions because this affects the number of raptors seen.  This year few routes have snow.

In a snowy year rough-legged hawks move south in Pennsylvania.  They breed in Alaska and Canada and winter in the Lower 48.  They’re found hunting in open meadows and brushy areas for mice, voles and rabbits.  But only where there’s snow cover.  If there’s snow, the rough-legs are here.  If not, they stay up north.

Two years ago we had a lot of snow — so much that it was hard to drive the routes.  (Remember the two feet of snow February 5-9, 2010?)   This year it’s easy to drive but the birding isn’t as good.

I’m not asking for a return to the snow of 2010 but snow in moderation would be nice, if only for rough-legged hawks.

Steve Gosser was lucky to see this one at Pymatuning on January 14.

(photo by Steve Gosser)

Atmospheric Effects

Weather & Sky

Yesterday the sky attracted my attention.

In the morning I saw thin lines of rain hanging from the clouds without touching the ground.

Virga!

Virga means “rod” in Latin and is the name for precipitation that evaporates before reaching the ground.  It’s very common out West where the air is dry and virga’s rapid evaporation causes high winds.

I tried to take a picture but the best of the virga drifted behind the ballpark lights.  In the middle of the photograph you can see “rods” falling and curling from the cloud.  Moments earlier there was more separation between the rain and the ground.  I just wasn’t quick enough.  Click here for a much better picture of virga.

The sky cleared at midday, then high, thin clouds moved in ahead of a cold front.  Way up there, above 20,000 feet, the air was filled with tiny ice crystals that caused an optical effect — a halo around the sun.

Halos are circular pastel rainbows that occur when sunlight passes in one side of the hexagonal ice crystals and out another side.  The light is doing this all over the sky but we typically see halos at 22o from the sun (or moon), though other angles are possible.

I can tell you it’s hard to take a halo’s picture because the sun confuses the camera.  I tried to block the sun with a telephone pole but that wasn’t enough.  I had to use my mitten too, so this photo is odd.

Click here for a better picture of a halo.

Keep looking up.  You may see some atmospheric effects.

(photos by Kate St. John)

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p.s. Late on Monday afternoon we had a mackerel sky (shown below).  Can you guess why it’s called that?