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.)

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  Its tongue has a zipper that opens in liquid and shuts when withdrawn.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.)

Several weeks ago I declared an end to my Friday bird anatomy series but this interesting diagram has prompted 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 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)

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 (arrow points to v.apt) 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.)

Scientists who study birds’ brains long ago discovered that, just like humans, birds can be right-handed or left-handed.

In humans, dominance on the left side of the brain results in right-handedness and vice versa.  Birds’ brains have functional lateralism too and can show behavior that indicates they favor one “hand” over the other.

An easy way to tell this is on birds whose eyes face sideways instead of straight forward (robins, pigeons, etc.) because they obviously use one eye or the other for important tasks.  What eye do they use to scan for predators?  In 2001, Franklin and Lima found that most dark-eyed juncos use their right eyes.

Crossbills take “handedness” one step further.  Their bills cross either to the right or the left.  Then they walk around the pine cones on which they feed in a clockwise or counterclockwise direction depending on the “handedness” expressed in their bills.

So, what do you think?  Is this crossbill right-handed or left-handed?

(photo of a white-winged crossbill by Raymond Barlow. Inspiration and information from Ornithology by Frank B. Gill)