Marcy Cunkelman’s Baltimore oriole agreed to return for a cameo appearance to illustrate another anatomy lesson.

Last week I pointed out that the part of the bird we call the “leg” is actually its foot.  The tibia is where its real leg begins.

In songbirds the tibia is feathered and usually unseen, hidden among the belly feathers.  Here, Marcy’s oriole is showing his tibia as he perches on her jelly dish.  What a surprise that his leg is orange!

In long-legged wading birds the tibia is naked and quite obvious because they need the tibia’s length to keep their bodies above the water.

We have tibias, too.  They’re the larger and stronger of the two bones between our feet and knees.  Above our knees the bone is called the femur. 

Birds have femurs but good luck trying to see them.  We’re lucky to see the tibia!

(photo by Marcy Cunkelman)

28 May 2010

Today’s anatomy lesson is about legs.

It’s easy to identify the birds’ toes, but where are their ankles and what’s in between?

Like cats and dogs, birds walk on their toes and look as if their knees bend backwards. Their “knees” are actually their ankles.

Between toes and ankles birds have a single bone, the tarsometatarsus, that’s the fusion of what would have been ankle (tarsal) and foot (metatarsal) bones if they were mammals.

This body part is called the tarsus. Plural is tarsi.

Fortunately we can still call it a “leg” in general conversation. 

(photo of a palm warbler by Chuck Tague, annotated by Kate St. John)

Let’s talk about toes.

We have five toes on each foot.  Birds have four.

Our five toes point forward.  Birds have three that point forward and one that points back(*).

We have a hallux — called a big toe — on each foot.  The bird has a hallux on each foot too.  It’s the toe that points back.

Here a Baltimore oriole is using his toes to perch on the edge of a jelly container.  In the first photo it looks like he’s fine with only his front three toes, but in the second you can tell that without his halluces (red arrow) he’d fall into the dish!

If our big toes pointed backward we’d be able to perch on edges too — but then we couldn’t wear shoes.

(* Note:  Osprey feet have three toes that point forward and a hallux that points back but osprey can rotate their outer toes backward. This makes a two-toes-front-two-toes-back arrangement that helps them carry fish.)

p.s.  See the comments below for more birds who have two-and-two toes.

(photo by Marcy Cunkelman of a Baltimore oriole diving into her jelly container to get a snack)

How do raptors catch their food? 

With their talons.

Talons are the claws on birds of prey and one of the two body parts that identify them as raptors, the other being their sharp beaks. 

On peregrines, the talons are especially long and deadly. 

The photo at left shows a peregrine’s feet on a rehabber’s glove with one talon circled in green.  See how long and curved that talon is?  About 3/4″ long.  Nearly as long as the first joint of the rehabber’s finger. 

And whose talon is this? 

Click on the photo to see PittStop, a female peregrine born at the Gulf Tower in 2003 who injured her wing when she hit a building that July.  She was taken to Medina Raptor Center in Spencer, Ohio and underwent flight training in the spring of 2004 to regain her wing strength after her initial injury healed.  That’s when this photo was taken. 

Unfortunately Pittstop’s injury was too extensive.  Her wing always droops, she cannot fly well enough to hunt, and she sometimes has damage-related seizures. 

Pittstop is now an educational bird at Median Raptor Center.  I’m glad they were allowed to keep her.

(photo by Chad+Chris Saladin, altered to illustrate the feet and talons)

23 April 2010

Imagine trying to keep your children warm on a cold night by hugging them to the outside of your winter coat. They will still be cold unless you open your coat and hug them to your skin.

Birds incubate their eggs and brood their chicks by “opening their coats” to keep their children warm. 

Feathers are great insulation so during the nesting season birds must develop a bare patch of skin — a brood patch — to allow the eggs to come in direct contact with their bellies.  The brood patch also has extra blood vessels close to the skin to heat the eggs.   At the end of the nesting season the blood vessels recede and the feathers grow back to keep the adult warm.

In species where only the female incubates, the male doesn’t develop a brood patch.  In peregrines, Birds of the World explains that both male and female peregrine have brood patches: “Both sexes have paired lateral brood patches.  Less well developed in male.” Peregrine couples share incubation.

If you watch the streaming webcams you’ll see the adult peregrines rock up-and-down and side-to-side as they settle on the nest.  This rocking opens the feathers that have curled over the brood patch and puts their skin in contact with the eggs or chicks.

Shown here is a brood patch on a female American kestrel, North America’s smallest falcon.  The person holding the bird reveals the brood patch and the downy black feathers surrounding it by blowing upward on the bird’s belly.  

Imagine how cold a brooding falcon can get in an updraft!

(photo by Jared B. Clarke, author of Bird Banding in Saskatchewan from his May 6, 2009 blog, Eggs have been laid)

For several weeks we’ve learned about body parts that are the same on birds and humans.  Today’s lesson is very different.

The cloaca is a bird anatomy part most people never see.  It’s under the bird and usually covered by feathers.

Cloaca (pronounced klo-A-ca) is a Latin word that means “to cleanse” and is aptly used to name the bird’s single opening for its urinary, intestinal and reproductive tracts.  Here it is on a great egret, circled in pink.

This multi-purpose “vent” may seem odd but male mammals have a single opening for urine and semen.  Birds economize further.  Everything happens at one location for them.

When birds mate, they touch their cloacas for a few seconds.  This brief “cloacal kiss” is just enough time to transfer semen to the female.

If you don’t like the sound of “cloaca” you can use the word “vent,” a prettier, alternative name.

(photo of the underside of a great egret, including cloaca, by Chuck Tague)

I have two easy anatomy terms for you this morning.

The side of a bird is on the side of its breast.  Here’s a female chestnut-sided warbler, with chestnut colored sides.  There used to be a bird called a rufous-sided towhee but it was renamed to “eastern towhee.”   He still has rufous-colored sides.

The flanks of a bird are on the sides of its lower belly. Here, a tufted titmouse illustrates this body part by showing off its rusty-colored flanks.  Titmice are white underneath except for this rust color which matches the brown dead leaves that hang on beech trees in winter.  I’ve read that this color helps camouflage the titmice.

(Chestnut-sided warbler photo by Chuck Tague. Tufted titmouse photo by Marcy Cunkelman. Both photos are altered to illustrate anatomy.)

Birds have bellies just like we do, low on their bodies just like ours. 

Occasionally the belly is a different color than the rest of the bird. 

Did you know that eastern bluebirds have white bellies?  My first field guide illustrated all the birds from the side, so I thought bluebirds had orange bellies just like robins.  I was quite surprised when I saw my first bluebird from the front.  The pink arrow shows you what I saw.

For really surprising belly colors, look at ducks.  When ducks swim their bellies are below the water line so you naturally assume their bellies match their breasts.  Not always. 

Check out the bellies on gadwalls, wigeons, and green-winged teal — if they’ll show them.  You’re in for a surprise.

(photo by Marcy Cunkelman)