Monthly Archives: January 2013

Walking Down Vortex Street

I know almost nothing about fluid dynamics but my article about wingtip vortices two weeks ago piqued my interest in the subject.

Last weekend I learned about this amazing phenomenon, the von Kármán vortex street, animated above by Cesareo de La Rosa Siqueira.

Von Kármán vortex streets occur when a fluid flows past a stationary object and generates a long line of vortices that swirl in opposite directions.  The phenomenon was named for Theodore von Kármán, the man who described it, and is probably called a street because it looks like one.

We usually don’t see von Kármán vortex streets in the wind, but it’s important that engineers plan for them.  If a tall structure is uniformly straight the vortices can make it fall down.  Click here to read about a famous mistake.

On a small scale, von Kármán vortex streets make telephone wires sing in the wind.  On a large scale they’re visible from outer space when clouds blow past a tall island.

Here’s a picture taken from the space shuttle that shows cloud cover blowing past Rishiri Island, Japan.  When the wind encounters Mt. Rishiri the clouds form a von Kármán vortex street on the downwind side.

Pretty cool, huh?

There are more than twenty islands that reliably generate von Kármán vortex streets.  Click here to see more pictures from NASA.

(Vortex animation by Cesareo de La Rosa Siqueira via Wikimedia Commons.  Space shuttle photo from NASA via Wikimedia Commons. Click on the images to see the originals)

A Look Back at 2012

Dorothy and E2 at the nest. 27 April 2012 (photo from the National Aviary falconcam at Univ of Pittsburgh)
Dorothy and E2 at the nest. 27 April 2012 (photo from the National Aviary falconcam at Univ of Pittsburgh)

Last May we saw the Pitt peregrines on the nestcam every day.

Since then we’d had a long, quiet, eight months but soon — by the end of February — our pair will be back on camera every day.

To get in the mood for the upcoming nesting season I created a slideshow of 2012 peregrine highlights from the University of Pittsburgh’s Cathedral of Learning.  Click on any photo to see the slideshow in its own lightbox.


(slideshow photos by The National Aviary falconcam at Pitt, Peter Bell, Donna Memon, Pat Szczepanski and Kate St. John)


p.s.  I wish I could have made a slideshow of the Downtown peregrines but they weren’t on camera last year.  If you’re in Downtown Pittsburgh, please watch for the peregrines and report what you see.  Click here for details.


Open Water

Female buffelhead at Bosque del Apache (photo by Steve Valasek)

The long spate of cold weather froze all our ponds and lakes.  Even the rivers were beginning to freeze until Monday’s warmth reversed the trend.

Don’t expect to see a lot of birds at Lake Arthur right now.  Waterfowl who rely on open water for food or to get airborne have left for open water.  Some are at our rivers, most have left town completely.

This female bufflehead was on the other side of the U.S. — at Bosque del Apache, New Mexico — when Steve Valasek took her picture.

No, she didn’t leave Pittsburgh for New Mexico, but Steve did.

(photo by Steve Valasek)

Heart Of Ice

An iceberg's heart, black ice growler, Greenland (photo by Kim Hansen on Wikimedia Commons)

Ice is on my mind this morning because of the freezing rain that began last night, so I couldn’t resist writing about this iceberg series by Kim Hansen on Wikimedia Commons.

The photo above shows a black ice growler (tiny iceberg) found at Upernavik, Greenland on Baffin Bay.  It’s one of the last intact pieces of a larger iceberg that broke apart while melting.

Black ice forms in a glacier when melt water refreezes in a crevasse without incorporating any air bubbles.  This ice is so clear that it takes on the color of its background.  Here it’s dark because of the sea.

Hansen and her friends retrieved the growler from the water.  Its surface was quite beautiful.
Surface of black ice growler (photo by Kim Hansen on Wikimedia Commons)


At first it was completely transparent but as it sat on the ground, exposed to sun and heat, it developed hairline cracks and began to turn white.  Click here and scroll down to see the experiment they tried on it.

This solid transparent ball, only two feet across, was hidden inside the iceberg until its last days on earth. It could have been the iceberg’s heart.

(photos by Kim Hansen on Wikimedia Commons)

Fanciful Eggs

We see chicken eggs every day so we tend to assume all eggs are plain and never shiny.  In reality most eggs are not.

Shown above is an illustration of 50 European bird eggs by Adolphe Millot published 1897-1904(*).

The eggs have many shapes and sizes from the goldcrest’s tiny pink oval (#19) to the large pointed pyriform egg of the now extinct great auk (#47).

Few are a single solid color but even those are amazing — from pink to robin’s-egg blue to a beautiful avocado color.  Tinamous are from South America so their eggs aren’t pictured here, but it’s worth clicking this link to see their glossy eggs in several colors.

The dark patterns on eggs are almost fanciful wreaths, caps, scrawls, dots, streaks and blotches.  They’re made by protoporphyrin which is deposited within or on the shell while in the bird’s uterus.  These dark spots are stronger than the plain calcium shell and tend to be deposited where the eggshell is thinnest.  Some birds lay on extra protoporphyrin when their personal calcium supplies are low.

And, as a final touch some eggs are shiny, some are waterproof.  I have read that duck eggs feel oily and that jacanas, who build floating nests, lay eggs that are lacquered (#29, in the top row).

Explore the eggs in the illustration using the quick key below.  If you click on the image you can zoom the original to read the egg numbers.

Illustration of European bird eggs from “ŒUFS” (Eggs) by Adolphe Millot from Nouveau Larousse Illustré [1897-1904], in the public domain via Wikimedia Commons.  (*) This image has been altered as described in the “p.s.” below.  Click on the image to see the original.

Inspiration for this Tenth Page is from an illustration on page 400 of Ornithology by Frank B. Gill.)

p.s.  Key to the illustration, copied from Wikimedia Commons:
The original French designation may not correspond to the modern French term. Eggs 1-50 are bird eggs, reduced in size by about a third.  Eggs 51-72, (*)which I erased from this illustration, were from turtles, reptiles, moths etc. I erased them to highlight only the bird eggs.  Click on the image above to see the complete original on Wikimedia Commons.

#    French        English
1    De bondree    honey buzzard (?)
2    De faucon    falcon (?)
3    D'epervier    Eurasian sparrow-hawk
4    De merle    blackbird
5    De grive    thrush
6    De freux    rook
7    De bruant proyer    corn bunting
8    De gros-bec    hawfinch (or perhaps another grosbeak?)
9    De moineau    sparrow
10    De pinson    chaffinch (or other finch?)
11    De pitpit    pipit
12    De bruant des roseaux    reed bunting
13    De coucou    cuckoo
14    De petit oiseau-mouche    hummingbird (?)
15    De bec-croise    crossbill
16    De troglodyte    wren
17    De sittelle    nuthatch
18    De rossignol    nightingale
19    De roitelet    Kinglet (Goldcrest?)
20    D'accenteur    accentor
21    De bruant fou    rock bunting
22    D'effarvate    reed warbler
23    De rousserolle    sedge warbler (or other Acrocephalus?)
24    De fauvette    warbler (??)
25    De mesange    tit (?)
26    D'hypolais    tree warbler
27    De jaseur    waxwing
28    De loriot    oriole
29    De jacana    jacana
30    De grouse (?)    grouse (?!)
31    De lagopede    lagopus
32    De faisan    pheasant
33    De perdrix    partridge
34    De caille    quail
35    D'avocette    avocet
36    De chevalier arlequin    spotted redshank
37    De pluvier guignard    dotterel
38    De pluvier de Virginie (??)    plover (??)
39    De vanneau    lapwing
40    De chevalier cul-blanc    green sandpiper
41    De sterne hybride (??)    tern (??)
42    D'hirondelle de mer    common tern
43    De sterne de Ruppell (??)    tern (??)
44    De goeland    seagull
45    De plongeon    loon
46    De guillemot    guillemot
47    De grand pingouin    great auk
48 & 49    De macareux    puffin
50    De grebe    grebe


Avian Reproduction reference

Peregrine Watchers Needed Downtown!

View of Pittsburgh from Mt. Washington tower (photo by Shane Cooper)
View of Pittsburgh from Mt. Washington radio tower (photo by Shane Cooper)

It’s peregrine courtship season and we have a mystery on our hands.

Last year the Downtown peregrines, Dori and Louie, abandoned their nest at the Gulf Tower and made a new one at the back of a building on Fourth Avenue (facing Third Avenue).  The new site was not as productive as the Gulf Tower, fewer eggs survived.

So the mystery is this:  Where will Dori and Louie nest in 2013?  Will they go back to Gulf?  Will they use the Third Avenue site?  Will they choose yet another place to nest?

Peregrine Watchers, we need your help Downtown to find out!

Keep your eyes peeled for the peregrines.  Where are they hanging out?  Report what you see as a comment on this blog or at the Pittsburgh Falconuts Facebook page.  Their location is the clue to their chosen site.


The Gulf Tower site is well covered by Make-A-Wish staff and the motion detection camera.  Glance at the building if you happen to be passing by.  Unfortunately peregrine visits have been rare here.


Vicinity of Third Avenue site:  In 2012 Dori and Louie hung out in this neighborhood and on this building.

The neighborhood is Third Avenue.  The building is Point Park University’s Lawrence Hall.

If you’re driving down Third Avenue from Grant Street to Wood, check the perches indicated by the red arrows. Is there a peregrine there?

If you’re walking down Third Avenue, glance at the perches on the back of the pink brick building on the right.

Note that Dori and Louie are not being seen in this neighborhood any more than they are at Gulf.

It is possible that they’ve chosen yet another place to nest.

So when you’re Downtown, keep looking up.  Check the building edges for peregrines.  Do this from Gateway Center to the Consol Center.  You might find the clue to the peregrines’ mystery.


QUESTIONS?  Leave a comment and I’ll get right back to you.

(photo of Downtown Pittsburgh by Shane Cooper.  Gulf Tower, Lawrence Hall and Third Ave photos by Kate St. John)

Choosing Camouflage

How smart are ground-nesting birds when it comes to hiding their eggs?

Scottish scientists report that Japanese quail are so smart they choose to lay their eggs where they’ll be best camouflaged.

Japanese quail are raised for meat and eggs so people already know they have highly variable eggshells.  Some females lay dark spotted eggs, others lay pale plain ones.  The eggs vary from female to female but the patterns are consistent for a given individual. (Click here to see a wide selection of egg patterns.)

To test whether the female birds were making camouflage decisions, scientists gave them a selection of four backgrounds on which to lay their eggs.

Females with spotty eggs chose backgrounds that matched the spots and hid their eggs in a disruptive pattern.  Females with plain pale eggs chose light backgrounds so their eggs blended in.

According to P. George Lovell of Abertay University and the University of St Andrews  “In this specific case, birds know what their eggs look like and can make laying choices that will minimize predation.”

But I wonder… Until a quail lays her first egg, how does she know what it will look like?  Can she plan for camouflage before she sees it?

Click here to read more about this study in Science Daily.

Photo of Japanese quail by K.Lin via Flickr account Hiyashi Haka, Creative Commons license. Photo of quail eggs from Wikimedia Commons. Click on the images to see the originals. )