Jan 20 2013

Wind Effect

Published by under Weather & Sky

As I write this morning before dawn, the wind is whipping around the house as a winter storm approaches from the west.

If I was at the roof peak I’d be blown away.  The wind is even faster up there (see red lines at top) where it converges to clear the house.

Outside my window on the downwind side, the air is swirling in updrafts like the turquoise lines at left.

I suppose I could find a few calm spots within the swirls if I went outdoors to experiment, but it’s not worth it.  At particularly gusty moments I hear garbage cans rattle down the alley in the dark.

(diagram by Barani on Wikimedia Commons.  Click the image to see the original)

3 responses so far

Jan 19 2013

Family Resemblance

Published by under Beyond Bounds

.

Doesn’t this bird look a lot like a red-bellied woodpecker?

This is a red-crowned woodpecker (Melanerpes rubricapillus), photographed by Charlie Hickey in Costa Rica.

There are nine Melanerpes woodpeckers that look very similar.  Most of them live in the tropics; some are island species.  I’ve noted below where you can see three species in the U.S.

Biologically speaking, this is more than a “family” resemblance  It’s at the genus level.

(photo by Charlie Hickey)

One response so far

Jan 18 2013

Why We Fly in V Formation

Why do swans, geese, and ducks fly in V formation?

Because it makes their journey easier.

Everything that flies experiences turbulence that slows it down.  Some of the turbulence is created by the act of flying.  For instance, during lift cones of swirling air called vortices roll off the wingtips and induce drag.

Here’s a dramatic NASA photo of a wingtip vortex, enhanced by red smoke.

 

The right and left wing vortices swirl in opposite directions — the left spins clockwise, the right counter-clockwise — resulting in two trailing swirls behind the airplane or bird.  Click here and here for videos.

The induced drag is especially hard on large or heavy birds (swans and geese) and birds with small wings relative to their size (ducks) so these birds line up in Vs to reduce the turbulence.

Here’s how it works.

In the photo below, four tundra swans are flying in the direction of the blue arrow.  Behind the leader, the blue lines show that each bird has its right wingtip in line with the left wingtip of the bird ahead of it.

 

Now I’ll draw the vortices and their spinning directions using blue for the left wing, red for the right wing.  Blue/left spins clockwise.  Red/right spins counter-clockwise.

When the blue vortex meets the red vortex at the wingtip, they cancel each other out.   By lining up in this fashion, each bird has one wing that experiences less turbulence.  That makes it easier to fly.

The lead bird is out there alone, though.  He’s the only one who gets no assistance so he tires before the rest of the flock.  The flock solves this by changing leaders when the first one needs to rest.  The lead bird drops back into the V and another bird takes his place.

Long, long ago birds solved the problem of wingtip turbulence.  When we invented airplanes we found out what it was all about.

 

(Credits:
Photo of tundra swans in blue sky by Chuck Tague.  Line of tundra swans by Marcy Cunkelman.  Red vortex photo by NASA via Wikimedia Commons; click on the image to see the original.
Today’s Tenth Page is inspired by a diagram on page 123 of Ornithology by Frank B. Gill.
)

7 responses so far

Jan 17 2013

Ravens Have Another Idea

Published by under Crows, Ravens

 

Just like the fighting gulls in Monday’s post, ravens will steal food but they have other ideas on how to go about it.

Watch this video from PBS NATURE’s Ravens.  You’ll be amazed.

(video on YouTube by PBS NATURE)

 

(p.s. The show is not this “Sunday at 8/7″ but it’s available online. Click on the Ravens link above to watch the full episode.)

4 responses so far

Jan 16 2013

It’s Hot Out Here!

Published by under Peregrines

On this cold, icy morning it’s hard to remember last summer’s heat, but after I published Jim Logan’s peregrine photos last week I learned about this hot young bird in Downtown Pittsburgh.

Just after 2:00pm on July 6, 2012, Rachel Papa looked out her 24th floor window in the Grant Building and saw a large raptor standing on the patio planter with its mouth open.

It was an unbanded immature peregrine falcon and he was panting.

The patio was in shade but it was not comfortable out there.  It was 97oF, 13o above normal on a hot day in the hottest year on record.

The peregrine merely gazed at Rachel as she took his picture through the window.

Here, the bird is alert and curious.

 

And here he seems to be saying, “I’m telling you, it’s hot out here!”

 

These photos show that the peregrines’ impromptu Fourth Avenue nest produced young last year, but our watchers saw only one fledgling not four or five as is usual at the Gulf Tower nest.

If Dori and Louie do the math and feel that the Gulf Tower is safe, they’ll go home to Gulf this spring.

We certainly hope so.  As @PittPeregrines says on Twitter, “Talons crossed!”

 

(photos by Rachel Papa)

2 responses so far

Jan 15 2013

Look Closely

Published by under Migration,Songbirds

If you merely glanced at this feeder from afar, you might assume all the birds are goldfinches.

They’re all the same size, but the two birds at the top are common redpolls, the latest arrivals in a massive irruption of winter birds.

In western Pennsylvania they’ve joined purple finches, red and white-winged crossbills, pine siskins, evening grosbeaks, and red-breasted nuthatches, all of whom came south because of the drought up north.

I’ve chronicled other irruptions (see list below) but I don’t remember a year in which so many species visited at the same time.  This year the only thing we seem to be missing are snowy owls.

Look closely at your feeders.  You might have some exciting visitors.

(photo by Marcy Cunkelman)

9 responses so far

Jan 14 2013

Fish Fight

I love this photo that Steve Gosser posted on Facebook last week. 

Textbooks describe ring-billed gulls as opportunistic feeders, “exploiting chances offered by immediate circumstances without reference to moral principle.”*

No respecters of age or experience, the top gull is a “teenager” (a second winter immature), the bottom one an adult. 

There are loads of fish in Lake Erie but one of them decided to steal a fish from his neighbor rather than catching one on his own.

Fish fight!

(photo by Steve Gosser)

 

(*) per Google’s dictionary

No responses yet

Jan 13 2013

Newton’s Third Law

Published by under Bird Behavior

In Physics class I learned Newton’s Third Law of motion:  For every action there is an equal and opposite reaction.

The woodpecker flies, the feeder swings.  You can see his thrust in the feeder’s tilt.

(photo by Marcy Cunkelman)

No responses yet

Jan 12 2013

Red Belly

Published by under Songbirds

The red streak on his belly gave the red-bellied woodpecker his name.

(photo by Marcy Cunkelman)

4 responses so far

Jan 11 2013

Lumping And Splitting

Published by under Tenth Page

In last week’s Tenth Page I mentioned that DNA test results can lead to lumping, splitting and reordering of bird species in our field guides and checklists.  Sometimes this drives me nuts.

An easy example of lumping occurred in December 2005 when the ABA lumped the black wagtail (Motacilla lugens) with the white wagtail (Motacilla alba).  The black one became Motacilla alba lugens.  They’re all the same species, just different races.

Splitting occurs more often as DNA analysis shows that birds we thought were a single species are actually two or more.  Some birders welcome the splits because they get new birds to chase for their Life Lists.  For me, it’s confusing … or exasperating.

Case in point:  Prior to DNA analysis the winter wren (Troglodytes troglodytes) was listed as a single species in Europe, Asia and the Americas.  In November 2010 the ABA officially split it into three (or more) species:

  1. Eurasian wren, Troglodytes troglodytes, in Eurasia. (new common name)
  2. Winter wren, Troglodytes hiemalis, in eastern North America. (new scientific name)
  3. Pacific wren, Troglodytes pacificus, in western North America. (new names all around)

Why does this drive me nuts?

Practically speaking you can only tell these wrens apart by range but in northeastern British Columbia “Winter” and “Pacific” overlap.  Can you tell them apart in the field?  Only by a slight difference in their call notes.  Can you tell them apart in a photograph?  No.  How to be sure which one you’ve found?  Test his DNA.

The changes are a bookkeeping nightmare.  The Internet is sprinkled with old and new names.  Some birds have changed twice: Baltimore oriole became “northern oriole” (lumped with Bullock’s oriole) and went back to Baltimore oriole (re-split).

I can’t keep up!  Arg!

 

(Photo of a winter wren by Steve Gosser taken in October 2010, only a month before the bird’s scientific name was changed.
Inspiration for this Tenth Page is from page 70-73 of Ornithology by Frank B. Gill.)

No responses yet

« Prev - Next »

Bird Stories from OnQ