Archive for the 'Bird Anatomy' Category

Dec 15 2012

Speaking of Plumage

Published by under Bird Anatomy,Songbirds

Speaking of plumage as I did yesterday

Here’s a bird in juvenile plumage.

If you didn’t know that immature white-crowned sparrows are cream-and-brown colored, you’d have trouble identifying him.

Here’s what his parents look like in basic plumage.

Quite a difference!

 

(photos by Marcy Cunkelman)

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Dec 14 2012

Plumage Basics

Birds molt at least once a year to replace worn out feathers.  This process permits them to wear different plumages.

Some birds, like the American robin, look the same before and after.  Others radically change their appearance by replacing their fancy breeding feathers with plainer plumes.  Male scarlet tanagers are an extreme example:  They’re red while breeding and green while not.

Molt and plumage terminology was standardized in 1959 by Humphrey and Parkes who divided plumage names into three main types. (*)

  • Juvenile plumage is worn by young fledged birds.
  • Basic plumage is what birds acquire during their annual post-breeding molt.  We often call this “non-breeding” or “winter” plumage but these terms are inaccurate.  Adult robins are always in basic plumage even when they’re breeding, and “winter” describes the weather North America is experiencing while the bird is away.  To South American birders, a green scarlet tanager is in summer plumage.
  • Alternate plumage is optional.  Some birds don’t undergo a second molt but those who do put on their finest feathers in time for the breeding season.  This is often called breeding plumage.

In some species it takes several years for the young to mature so they progress through as many plumage cycles as it takes to become adults.  Young ring-billed gulls go through three cycles:  Basic 1, Alternate 1, Basic 2, Alternate 2, Basic 3, Alternate 3. Gulls are complicated.

American avocets aren’t quite so complex.  They molt their wing feathers once a year but change out their head and neck feathers twice a year from basic plumage (white) to alternate plumage (ochre) for the breeding season.

The avocets above are lined up in perfect sequence during their post-breeding molt in August.  The bird standing on the left is closest to basic plumage, the bird on the right is closest to alternate plumage, and the bird in the middle is halfway between.

 

Below, another flock has the lead bird closest to alternate plumage and the trailing bird closest to basic.

Look closely at each bird and you can see that the wings of the 1st, 3rd and 4th birds have ragged trailing edges because they’re molting their wing feathers.  The 2nd and last birds have perfect wings, so my guess is that they’re juveniles.  Juveniles don’t molt their fresh new wing feathers until they’re a year old.

When avocets have completed their molt into basic plumage their heads and necks are gray-white like this bird photographed in September.

 

Experts in molt and plumage can probably tell the age of these birds by their appearance.

Not I.  Aging shorebirds by plumage is my final frontier.

(Inspiration for this Tenth Page is from page 110 of Ornithology by Frank B. Gill.
All photos by Bobby Greene
)

 

(*) If you’re a plumage expert, please feel free to correct me.  I’m still learning!

P.S. TO PEREGRINE FANS:  Molting is a wonderful thing.  Last May the male peregrine at Pitt, E2, chased off an intruder but not before this opponent damaged one of his primary feathers.  This gave him a “hole” in his wing.  Over the summer he completed his annual pre-basic molt and grew all new feathers.  Now his wings are perfect.  No gap.

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Nov 30 2012

Form, Function, and a Quiz

All birds have feathers, wings and two legs but they certainly don’t look alike, not even in silhouette.

Birds in the same family can look very different.  Take sandpipers (Scolopacidae) for instance:

  • Sanderlings are small sandpipers with short legs and a short pointy bill.
  • Whimbrels are more than twice the sanderlings’ size with relatively short legs and a long down-curved bill.
  • The critically endangered spoon-billed sandpiper is smallest of all with short legs and a spoon-tipped bill.

Why are they so different?  Their features have evolved to match their lifestyles.

  • Sanderlings chase waves to catch invertebrates tossed on sandy beaches.  They need to be quick so it’s important to be close to the ground and able to pick up prey quickly.
  • Whimbrels use their long curved bills to probe the mud of salt marshes and tidal flats to find crabs and invertebrates.
  • Spoon-billed sandpipers sweep their bills side to side in shallow water to capture prey.  Like the roseate spoonbill their lifestyle has shaped their bills.

In architecture, form follows function.  In birds their form happened first, then the birds with better features survived.

 

And now for a Quiz!

Every time I look at the silhouettes, I find myself trying to identify the birds.  There are 26 individuals and 3 flocks in the image.  How many of the silhouettes can you identify?

Tips:  I’ve numbered the individuals and marked the flocks with letters below. Assume each flock is made up of the same species.  Some of the 26 individuals are repeats.  If you can’t identify the exact species, name the bird by group, as in “gull.”

Post your answers in the comments.  Good luck!


(Inspiration for this Tenth Page is from page 10 of Ornithology by Frank B. Gill.  Bird silhouettes from Vectorilla.com. Click on the image to see the original)

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Nov 23 2012

How Birds Improved Upon Their Past


Last week I wrote about the Urvogel Feather of Archaeopteryx lithographica, the oldest feather ever found.  Now that I’m beginning the Tenth Page series I’ve discovered that page 30 of Ornithology has a neat comparison of Archy’s skeleton to that of modern birds.

Archaeopteryx lithographica is recognized as a link between dinosaurs and birds because he has features of both.  Like dinosaurs he has**:

  • jaws with sharp teeth
  • three fingers with claws
  • a long bony tail
  • hyperextensible second toes that are “killing claws”
  • feathers, which also suggest homeothermy (This characteristic is rather self-fulfilling in that dinos were not thought to have feathers until Archy was discovered.)
  • and various dinosaur skeletal features.

Like birds he has:

  • flight feathers, the asymmetrical feathers on his wings
  • broad wings
  • hollow bones
  • a furcula, the “wishbone”
  • and reduced fingers.

But as a bird he’s not quite there yet.  Modern birds have skeletal adaptations that make flight much easier than it must have been for Archy.  This is evident in a skeletal comparison.

Page 30 of Ornithology describes how modern birds improved on Archaeopteryx lithographica’s features:

  1. Skull: In modern birds the braincase is expanded and the bones are fused.
  2. Hands: Most of the bones are fused
  3. Pelvis: Bones are fused to make a sturdier structure
  4. Tail: Bones are fused, the tail is shorter
  5. Sternum: Expanded to a large keel for attaching the flight muscles
  6. Rib cage: Has cross-struts (“horizontal uncinate processes”) for strength.

So, if you have a lot of time to improve your flight abilities — say 150 million years — this is what you get.

Inspiration for this Tenth Page is from page 30 of Ornithology by Frank B. Gill.

(credits:
** The dino list is quoted from the Wikipedia article on Archaeopteryx.
Photo of Archaeopteryx lithographica, Solenhofener specimen from Wikimedia Commons.  Skeleton of modern bird from Illustrations of Zoology by W. Ramsay Smith and J S Newell, in the public domain via Wikimedia Commons, red annotations added by Kate St. John.  Click on the images to see the originals.
)

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Oct 28 2012

Racket Tips

The blue-crowned motmot is a colorful Central and South American bird with a striking face and red eyes.  The male also has two unusual tail feathers with bare shafts and racket tips.  Racket… as in tennis racket.

The  feathers don’t start out this way.  When the male molts the feathers grow in normally but the middle radii are weakly attached to the shaft so they easily fall off during normal abrasion and preening.  The result is a fancy tail during the breeding season.

In the wild, the racket tips are very noticeable because the males swings his tail like a pendulum when disturbed.

Want to see a blue-crowned motmot in Pittsburgh? Visit the National Aviary.

(photo from Wikimedia Commons.  Click on the image to see the original)

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Mar 09 2012

An Ancient Grackle?

Published by under Bird Anatomy

 

If you ever saw this bird, you might think it was a cross between a grackle and a scissor-tailed flycatcher because of its iridescent blue-black color and long, thin tail feathers.

But it’s not a bird.  This is a drawing of a Microraptor, a pigeon-sized dinosaur that lived 130 million years ago.  We know what it looked like thanks to extensive research published in yesterday’s issue of the journal Science, and this image by Mick Ellison of AMNH.

The research was a collaboration of American and Chinese scientists who examined Microraptor’s fossilized feathers at the microscopic level. 

The iridescence breakthrough has an Ohio connection.  Dr. Matt Shawkey, a co-author of the study and associate professor of biology at the University of Akron, discovered that in the commonly iridescent feathers of modern birds, arrays of pigment-bearing organelles called melanosomes were uniquely narrow.  These same shapes were found in Microraptor melanosomes.

Want to learn more about this dinosaurThe American Museum of Natural History will have a live video chat today (Friday, March 9) at 12:30pm to discuss this earliest record of iridescence.

For more information, pictures and videos visit this page on the American Museum of Natural History’s website.

(drawing of a Microraptor based on digital overlays of nine fossilized specimens, by AMNH/Mick Ellison. Image featured here on Science Daily)

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Jan 24 2012

Feather Facts to Impress Your Friends

Published by under Bird Anatomy

Did you know that… ?

  • For most birds, feathers make up 5-10% of their total weight but are two to three times heavier than their skeletons.
  • Tundra swans have 25,000 feathers, 80% of which are on their heads and necks.
  • Doves and herons have some specialized “powderdown” feathers whose barbule tips disintegrate into a talcum-like powder.  These feathers grow continuously so they can do this.
  • Dark feathers are stronger than white feathers.  The dark pigment melanin provides strength.
  • Feathers are held in place on birds’ bodies by follicle muscles. Some birds, such as nightjars, experience “fright molt” when something scary causes those muscles to relax and the bird loses some feathers.
  • Owls have fringe-like leading edges on their primary feathers and long filament-like barbules on other feathers.  These features reduce air turbulence, allowing owls to fly silently.
  • Archaeological evidence indicates feathers first appeared on meat-eating dinosaurs.    (Peregrines’ ancestors!)
  • Desert sandgrouse in Africa have specialized belly feathers that can absorb and carry water.  The male sandgrouse flies as much as 18 miles from his nest to a watering hole where he soaks his belly in the water.  He then flies back to the nest where his young squeeze his belly feathers in their bills to get a drink.  (Pictured above is a male Namaqua sandgrouse in the Kalahari.)

(photo by Chris Eason, via Creative Commons License on Wikimedia Commons.  Click on the photo to see the original.)

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Sep 02 2011

Amazing Tongues … With Zippers

Published by under Bird Anatomy

Yesterday’s nasturtium looked inviting to a hummingbird, but how does he drink its nectar?

This Science Friday video — originally published on May 27, 2011 — shows how both the dog and the hummingbird use their tongues to drink.

The dog drinks by sucking liquid up in a column, not by using its tongue as a ladle to its mouth.

The hummingbird is even more amazing.  Its tongue has a zipper that opens in liquid and shuts when withdrawn.  It holds the liquid inside its tongue.

Watch and see!

(video from Science Friday)

p.s. What kind of hummingbird is this?  (I have no idea.)

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Mar 18 2011

Anatomy: Field of View

Published by under Bird Anatomy


Several weeks ago I declared an end to my Friday bird anatomy series but I found this interesting diagram so here’s an unscheduled lesson.

Field of view is the angular extent of vision at any given moment.  It’s basically “all you can see without moving your eyes.”

Prey species, like pigeons and robins, usually have a very wide field of view because they need to see danger coming from any direction.  To achieve this most of their vision is monocular, like our peripheral vision, with only a narrow angle of binocular vision with good depth perception.  It’s so important for them to see what’s coming that some prey species can move each eye independently!

As shown above a pigeon can see nearly 360 degrees around its head, a real advantage when avoiding a peregrine.

Predator species usually have a narrower field of view because they need to have good depth perception in order to capture prey.  The owl’s field of view is more like ours with a wide area of binocular vision and narrow bands of peripheral, monocular vision on either side. 

Peregrines and people have fields of view similar to the owl’s.  Ours is actually wider than the diagram.  We can see 180 degrees. 

Here’s how you to find your field of view, which is basically a test of your peripheral vision.  Hold up your index finger in front of your nose and close one eye.  While looking straight ahead, move that finger around your head toward the ear near your open eye.  When you can no longer see your finger, that’s where your field of view ends. 

Now find out where your binocular vision ends.  Open your closed eye, close your open eye (i.e. switch eyes).  Look straight ahead and move your finger in the same direction as before.  When you can no longer see your finger, that’s where your binocular vision ends.

Of course, these tests only work if you have good vision in both eyes.

(illustration from Wikimedia)

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Feb 25 2011

Anatomy: Pterylae

Published by under Bird Anatomy

Fifteen months ago I started this Friday series on bird anatomy as a project for the winter of 2009-2010.  Now, 67 entries later, I’m declaring that winter is over and freeing up my Fridays for time to write about spring flowers, bird migration, and peregrines.  This is the last regularly scheduled anatomy lesson but it’s not the last blog I’ll ever write on anatomy.  Who knows?  I might change my mind and restart the series in July.  ;)

Today’s topic was suggested by Tony Bledsoe when I posted a photo of a warbler whose belly feathers were blown aside to expose its fat reserves.  We can see birds’ belly skin because their feathers are arranged in tracts. 

Unlike mammals whose hair sprouts uniformly from the skin, most birds’ feathers sprout in tracts called pterylae with bare patches of skin between them.  Pterylae are like forests of feathers and that’s what the word means: pteron is “feather,” hulé is “forest.”  The bare patches between them are called apteria:  “without feathers.”

Shown above are the pterylae of a rock pigeon.  You can see from the illustration that there are apteria on the neck and belly but we rarely see a bird’s bare skin because their feathers fan out to cover their bodies.  It’s interesting to realize that the bare spot on the belly is a good beginning toward a brood patch for incubating eggs and brooding young.

Some birds are exceptions to this rule.  Penguins’ feathers sprout uniformly across their bodies.  You can’t blow on a penguin’s belly and see its skin.  

I’ll bet the lack of pterylae explains why penguins don’t use their bellies to incubate their eggs.  They use their bare feet!

(clip art from the Florida Center for Instructional Technology (FCIT) at University of South Florida.  Click on the image to the see the FCIT clip art library.)

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