Archive for December, 2009

Dec 06 2009

Winter beauty

Published by under Weather & Sky

Latodami Field, North Park, 29-Nov-09 (photo by Dianne Machesney)
Winter in Pittsburgh is mild compared to Pennsylvania's northern and mountainous regions. 

Yesterday it snowed but didn't stick - at least in my neighborhood.  We usually don't have snow cover in the city until late December, and then it's likely to melt.  Even so, a snowless winter can be beautiful when the sun shines, as it will today. 

Here's a photo Dianne Machesney took a week ago at Latodami's upper field in North Park.  The muted browns of winter have a special kind of beauty.

(photo by Dianne Machesney)

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Dec 04 2009

Anatomy: Secondaries and Tertials

Published by under Bird Anatomy

Bald eagle with secondaries and tertials marked (photo by Chuck Tague)
Today I'll wrap up the wing's flight feathers, parts two and three, secondaries and tertials.

Like the primaries we learned about last week, secondaries and tertials are remiges.  The secondaries run from the wrist to the elbow and hang from a bone called the ulna.  They're marked here in pink.  Tertials, marked in yellow, run from elbow to armpit and hang from the humerus.  If humans had wings our secondaries and tertials would hang like the sleeve fringe on a buckskin jacket.

The number of secondary feathers varies depending on species, from six in small birds to 40 for an albatross.  Tertials are always few and usually hard to see in flight, especially on songbirds who have 9-10 primaries, 6 secondaries and only 3 tertials.

Tertial feathers are rarely mentioned except in shorebird identification.  That's because shorebird wing structure is so different that their tertials nearly cover their primaries when their wings are folded.  In fact, when at rest, their tertials lay on top of their tails instead of over their backs.  If I was good at shorebird identification I would be able to look at the tertials and come up with the correct species.  I'd even be able to age the bird.

And finally, even jets have movable secondaries and tertials - or so I like to think.  When birds land they cup their wings and drop their secondaries and tertials to create drag and slow down.  When a jet lands, it lowers two sets of flaps on its wings to do the same thing.

Watch a pigeon land, then watch a jet and you'll see what I mean.

(photo of a juvenile bald eagle by Chuck Tague, modified to show the secondaries and tertials)

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Dec 03 2009

Beyond Bounds: American Avocets

American Avocets at Bombay Hook (photo by Kim Steininger)
Now that I've been writing this blog for more than two years (time flies!) I've accumulated a stockpile of photos from friends.  Many of the pictures are stunning but I never get a chance to use them when I write about local birds in season.  So I have a plan.

Today I'm starting a weekly series for this winter that I'm calling Beyond Bounds, a celebration of superior photos of birds that you won't find in southwestern Pennsylvania.  

American avocets lead the list.  The Pittsburgh area is rarely graced by the visit of a single avocet and we never see flocks like this.  Kim Steininger captured these at Bombay Hook, Delaware. 

Aren't their patterns cool?  Yes, beyond bounds.

(photo by Kim Steininger)

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Dec 02 2009

What a Moon!

Published by under Musings & News

Full Moon (photo by Chuck Tague)
The sky was clear, the full moon bright.  Last night my backyard was flooded with light as bright as day.

The trees and even the twigs cast shadows.  If I was a mouse there would be no hiding from an owl in that silvery light.

Above the Arctic Circle the sun set on September 21 inaugurating six months of perpetual darkness - or so I thought until the moon reminded me that once a month everything is revealed.

I imagine last night on Banks Island.  The sea ice glints in the moonlight.  An arctic fox crouches to pounce on a lemming.  A raven scans the ice for seal guts, remains of a polar bear's meal.  Night is turned to day.

The Snow Moon will wane.  In two weeks time only stars will illuminate the scene.  The night will be dim until the next full moon - a Blue Moon - on December 31.

(photo by Chuck Tague.  See Chuck's moon-watch in Florida and his Full Moon Schedule for 2010.)

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Dec 01 2009

Christmas Fern

Published by under Plants

Close-up of Christmas Fern (photo by Dianne Machesney)
Welcome to the Christmas month.

When you take a walk in December's woods you'll find very little green except for this plant, the Christmas fern, Polystichum acrostichoides, so named because it's green during the holidays.

Christmas fern is a common, evergreen, perennial fern that grows in the woods in most of eastern North America.  It's one of the few ferns I can recognize because its leaflets are shaped like Christmas socks or like Santa's sleigh.  (To see the sleigh shape turn the leaflet sideways with the "thumb" pointing up.)   From afar the plant looks like a clump growing in well-drained rich soil.

People used to use this fern in Christmas decorations, though I must say I prefer pine for its Christmas-y smell. 

Keep your eyes open for this splash of green.  It brightens December's short days. 

(photos by Dianne Machesney)

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