It’s Friday! and time for the Bird Anatomy lesson.

As I said last week we’ve hit a patch of easy anatomy terms as we move down the underside of the bird.

Today’s body part is the breast.   And here’s a rose-breasted grosbeak to illustrate its location. 

Under those rosy feathers are the breast muscles, the largest, strongest muscles in the bird.  They are so large they comprise 15-20% of its body weight. 

They’re the flight muscles that pull the wings both up and down.  In most birds the downstroke is the power stroke, so those muscles are the largest.  The upstroke muscles return the wings for the next flap and are ingeniously rigged like pulleys to make the job easier. 

You can see these structures in a whole chicken breast from the grocery store.  Chickens have been selectively bred to produce a tasty bird for humans so what you see on a grocery store bird doesn’t have quite the same proportions as what the peregrine sees when he dines on a pigeon, but you’ll get the idea.

(See how I couldn’t help but include peregrines in this?)

(photo by Marcy Cunkelman)

It’s been “All Peregrines, All The Time” for the past week but for those of you following the anatomy lessons, never fear.  The series continues every Friday (barring a peregrine “emergency”) because I haven’t gotten halfway through the bird yet.

We’ve just reached the underside where the body part names are often the same ones we use to describe our own anatomy, so you’re going to have an easy time of it for a while.  Stay with me, though.  It will get interesting later on.

First up is the throat and the best bird to illustrate this is a male ruby-throated hummingbird.  Just in case you’re wondering where his throat is I’ve pointed to it with a pink arrow.

The throats on female ruby-throated hummingbirds are white.  The males have iridescent red feathers which only look this red when the light catches them just right — and then they’re so red they knocks your socks off.

Yes, the throat on a bird is where you’d expect it to be.

(photo by Marcy Cunkelman)

Dorothy’s egg pre-empted my normal Friday anatomy lesson.  Now that the first excitement is over, I can resume our regular programming (as we say in the TV business) with a bird anatomy lesson you can apply right away. 

In the spring, the lores on many birds become colorful in preparation for breeding.

What are the lores?  The lore (singular) is the space between the bill and the eye, indicated by the pink arrow.  Since there are two of these spaces, the word is usually plural. 

The lores are often featherless on water and wading birds.  Even so they turn gorgeous colors in the spring.  Click to see the beautiful green lores on this great egret and the yellow ones on this double-crested cormorant.   

Closer to home, I’ll be watching the lores on white-throated sparrows.  They become bright yellow, a pretty sign of Spring.

(photo of white-throated sparrow by Marcy Cunkelman.  Click-through photos by Chuck Tague)

This great horned owl is winking sideways!

He’s closing his nictitating membrane.

The nictitating membrane, or third eyelid, is named for the Latin word “to blink” (nictare).   Its function is to protect and moisten the eye while allowing the animal to see.  Sometimes the membrane is transparent, sometimes translucent.  It depends upon the species.

Birds, reptiles, fish and amphibians have nictitating membranes but in most mammals it’s only a vestigial remnant in the inside corner of the eye.  Mammals who swim frequently, such as polar bears and beavers, are one exception to that rule.  They have transparent, fully functional third eyelids which they use like underwater goggles.

Though all birds have nictitating membranes it’s rare to see birds blink.  Sometimes you can capture a raptor blinking because its eyes are so big and it uses its third eyelid a lot.

Birds of prey close their nictitating membranes while capturing prey.  They can’t afford to have the prey scratch their eyes!  Peregrines rapidly blink their nictitating membranes while diving at top speed and close them while feeding their sharp-beaked young.

Having said it’s hard to see a bird blink, I’ll show you two examples.

Here’s a female peregrine with her third eyelid closed.  Notice that it’s white.

And here’s a Eurasian collared dove with its eyes closed.

It’s all in the blink of an eye.  😉

(photos by Chuck Tague)

Here’s a conundrum:  All birds have crowns but not every bird is crowned.

In bird anatomy the crown is the top of the head.  All birds have one and it’s usually unremarkable.  When the crown is pretty or a different color the bird is often named for it.  Thus the white-crowned sparrow pictured here. 

I usually see white-crowned sparrows from the side or below with little opportunity to examine their crowns, so this picture is a rare treat.  Notice how the edges of his crown are jagged.  If they were straight the white patch would probably be called a stripe.  The elaborate crown camouflages this bird in dappled sunlight and he raises it to claim territory.  Pretty cool. 

Surprisingly there are not many “crowned” birds in North America and even fewer in southwestern Pennsylvania.  Here you’re likely to see only these:

• Black-crowned night-heron
• Ruby-crowned kinglet
• Golden-crowned kinglet
• Orange-crowned warbler
• White-crowned sparrow

And of those listed above, you’ll be lucky to see the crowns on the kinglets and warbler.  They only raise it when they’re excited.

(photo by Marcy Cunkelman)

The word “crest” describes a lot of things —  the crest of a hill, the crest of a wave, the crest on a helmet, the crest of a roof — but its primary meaning is “a comb or tuft on a bird’s head.”

Blue jays, tufted titmice and northern cardinals have noticeable crests that they raise or lower depending on their mood.  Most of the time their crests appear to be in the “up” position but a really excited cardinal can raise its crest even further, as shown at this link.

Some birds have “crest” in their names.  This is an immature crested caracara, a Central and South American bird that also lives in Texas and Florida.  (I can tell it’s immature because of its brown plumage and pink cere.)

The crest, indicated by an arrow, looks almost like long flowing hair.  When a crested caracara gets excited the “hair” stands up on the back of his head.

After Chuck took his picture, this bird got excited and raised his crest.  He looked so funny I nearly laughed.  Click on his photo to see why.

(photos by Chuck Tague)

12 February 2010:

If you thought we were done with bird anatomy because we reached the tail last week, think again. 

There are plenty of obscure anatomical words that I haven’t covered yet.  For instance, what about axillaries?

Axillaries are the bird’s armpits, circled above in yellow.  Usually they’re unremarkable because they’re a single color but every once in a while there’s a surprise. 

For instance, notice the American robin above and the black-bellied plover below.

And how about this illustration of rose-breasted grosbeaks? Who knew that the males have rosy armpits and the females have yellow?

If birds don’t soar, we get only a fleeting glimpse at their axillaries.

(photo credits: American robin by Marcy Cunkelman, black-bellied plover by Chuck Tague, rose-breasted grosbeak illustration from Wikimedia Commons; click on the caption to see the original)

Having covered the nape, mantle and rump we’ve gotten to the end of the bird and can now talk about its tail.

Rectrices is a word for tail feathers that’s not often used.  I find it hard to remember because it resembles another feather word, remiges, and because I tend to mispronounce both of them.

The good news is that information on the origin of these words makes it easier to figure out their meanings.  Here’s how.

Rectrices (pronounced REK.tris.iz) are the strong tail feathers that direct the bird’s flight.  Rectrix is the singular form.  When you see them spelled side by side, it’s pretty obvious that rectrix and direct come from the same Latin word.

Remiges (pronounced REH.midg.iz) are the wing’s flight feathers.  Remex, its singular form, comes from the Latin word for oar and used to mean “rower.”   Watch a crow fly and you’ll see his wings rowing through the sky.

So the remiges are for rowing and the rectrices are for directing.

Wings row.  Tail directs.  Maybe now I’ll remember.

(photo of a great-crested flycatcher showing off his cinnamon rectrices, by Chuck Tague)

Here’s a bird who’s a natural for today’s anatomy lesson.

What’s that splash of bright yellow on this otherwise drab bird?  It’s his rump and it gave him his name:  yellow-rumped warbler.

Not only is this bird showing off his namesake but you can see a V of gray-edged dark feathers below his rump that overlap like shingles on a roof.  These are his upper tail coverts, the feathers on the top side of his body that cover his tail.  The pink arrow is pointing to them.

Upper tail coverts are usually bland feathers shorter than the tail, but peacocks have overturned that rule.  Their fancy “tails” are actually very long upper tail coverts that they raise during courtship display.  When they do this, they reveal a relatively small tail.

While our yellow-rumped warbler is paused, let’s use him to review some earlier anatomy lessons.

Can you see his nape?   It’s plain and gray compared to his mantle which has long dark stripes on a brown background.  If you look closely you can see the scapulars on his right wing, edged in brown.  They’re draped over his primary upper wing coverts whose feathers are edged in white.

This yellow-rumped warbler is in basic (i.e. winter) plumage and is posed in a way that hides the field marks on his sides and head that indicate his sex.  If he’s a male, he will molt his brown feathers and become black and white in the spring – but he’ll always keep his bright yellow rump.

What a cooperative bird!  Chuck Tague photographed him in Florida where yellow-rumped warblers are very common in winter.

(photo by Chuck Tague)