Category Archives: Bird Anatomy

Why Don’t Sleeping Birds Fall Off the Branch?

African gray parrot and common grackle, each sleeping on a perch (photos from Wikimedia Commons)

2 December 2021

We take for granted that birds sleep on a perch without falling off, yet we drop whatever we’re holding when we fall asleep. (Many’s the time that my book falls off the bed!)

How do birds continue to hold on after they fall asleep? The answer is in this vintage article.

(photos from Wikimedia Commons; click in the caption to see the originals)

Do They See What We See?

GG looks up from a meal (photo by Chad+Chris Saldin)

30 November 2021

We humans assume that what we see is what everyone else sees, including other species. But this isn’t so.

Peregrines see much finer details at a greater distance that we do. The details don’t blur for them in a 200 mph dive. (Click the link to learn more.)

Tellus in a stoop (photo by Chad+Chris Saldin)

Cats cannot see red-green nor distant details, but they see much better in the dark. Who needs distance vision while looking for a nearby mouse at night? Click here to see photos of our vision versus cats’. Notice the normal vs. red-green-color-blind examples below.

Domestic cat (photo from Wikimedia Commons)
Normal vision vs deuteranopia (red-green color blind) (images from Wikimedia Commons)

White-tailed deer see regular blaze orange as gray but if the orange has fluorescence it stands out for them. Their vision is best in the blue range so that they see well in twilight.

White-tailed deer at Schenley Park (photo by Kate St. John)
Non-fluorescent blaze orange looks gray to deer ( sign from PA Game Commission, Blaze Orange Vest on Amazon)

Birds see ultraviolet light though we cannot. Here’s how we know this and a hint at what birds look like in ultraviolet light.

Do other species see what we see?

No. Birds see more.

(peregrine photos by Chad+Chris Saladin, deer photo by Kate St. John, remaining photos from Wikimedia Commons)

How Birds Chew

Cedar waxwing about to swallow whole fruit (photo by Steve Gosser)

28 October 2021

Have you ever noticed that birds gulp their food? Of course they don’t chew — they don’t have teeth — but much of what they eat still has to be “chewed” before they can digest it.

That’s where grit comes in.

Gravel (photo from Wikimedia Commons)

Birds chew with their gizzards, a specialized stomach with thick muscular walls that grind up food, often aided by particles of stone or grit.

Diagram of bird digestive system, annotated (image from PA Game Commission)

Birds regularly eat grit to aid their digestion, as Ecco is doing in the photo below.

Peregrine falcon, Ecco, ingesting gravel (photo from the National Aviary snaphot camera at Univ of Pittsburgh)

So when you see birds swallowing things whole rest assured they’re chewing inside … in the gizzard.

Red-tailed hawk with prey (photo from Wikimedia Commons)

p.s. Other animals have gizzards too including crocodiles, alligators, mullet (a fish) and earthworms.

(photos from Steve Gosser, Wikimedia Commons, and the National Aviary snapshot camera at Univ of Pittsburgh)

Birds With Teeth?

Ostrich face (photo from Wikimedia Commons)

4 October 2021

Teeth are so important that every toothless animal today is descended from ancestors that had them. This includes anteaters, baleen whales, pangolins, turtles, and birds.

Giant anteater with his snout in an ant hole (photo from Wikimedia Commons)

The ancestors of birds were theropod dinosaurs. They definitely had teeth.

Velociraptor, a theropod ancestor of birds (image from Wikimedia Commons)
Tyrannosaurus rex, skeletal head (photo from Wikimedia Commons)

Then about 116 million years ago a common ancestor of all birds developed genetic mutations that inactivated the genes for tooth formation. Eventually birds’ teeth disappeared, replaced by horn-like beaks.

There are probably several reasons why teeth disappeared but the main one is this: In order to fly well it’s important to reduce excess body weight. Bones and teeth are heavy so over time birds evolved hollow bones and toothless beaks. They compensate for the lack of teeth by chewing food in their gizzards.

American robin taking flight (photo from Wikimedia Commons)

They also compensated by using their beaks as multi-purpose tools to grasp, twist, pry, crack open shells, and sever tendons.

Each species developed a beak for its lifestyle. A few of them evolved beak modifications that resemble teeth.

Among tooth-billed hummingbirds (Androdon aequatorialis) the males have a “straight bill with a prominent hooked tip and backward-pointing tooth-like serrations on the distal half. The modification is absent on the female bill, and thus may be related to sexual selection,” describes Birds of the World. Perhaps the “teeth” are used for fighting.

Toothbilled hummingbird beak (photo from Wikimedia Commons)

The critically endangered tooth-billed pigeon (Didunculus strigirostris), the national bird of Samoa, has a stout curved bill with a specially toothed lower mandible.

[The bill] is adapted to feed on Wild Mahogany Dysoxylum spp. fruits, although first-year birds apparently cannot do so. These fruits have a tough capsule that it is able to open using its strong bill, removing the flesh using a sawing action with the lower mandible.

Birds of the World, Tooth-billed pigeon account 

If you want to stretch the definition of “teeth” peregrines have two of them. The tomial tooth on each side of the upper beak is used “to kill prey quickly by biting their necks and severing the vertebrae.”

Peregrine falcon showing tomial teeth on upper mandible (photo by Chad+Chris Saladin)

Does that make them birds with teeth? Not really. No dentin, no enamel, and they aren’t using them to chew.

(photos from Wikimedia Commons; click on the captions to see the originals. Peregrine photo by Chad+Chris Saladin)

Wry and Awry

Wrybill, New Zealand (photo from Wikimedia Commons)

10 September 2021

When I think of the word “wry” the first thing that comes to mind is sarcastic or dry mocking humor. “He made a wry comment” and everyone smiled like this:

Wry smiles: cat emoji and Gianni Gambi in 1937 (images from Wikimedia Commons)

At its root “wry” means twisted, bent or turned abnormally to one side. Two birds have “wry” in their names and their bodies show it.

The wrybill (Anarhynchus frontalis) is a plover endemic to New Zealand whose bill is permanently twisted, always to the right.

Wrybill in hand and illustration of bill (images from Wikimedia Commons)

The Eurasian wryneck (Jynx torquilla) is named “twisted neck” but his neck is straight …

Wryneck (photo from Wikimedia Commons)

… until he gets frightened.

All birds can twist their necks to preen, as Ecco demonstrates this week at the Pitt peregrine nestbox.

But the wryneck moves his neck in an mesmerizing way to distract predators.

We stop and stare when his neck is awry.

(images from Wikimedia Commons; click on the captions to see the originals)

A Tip For Identifying Confusing Fall Warblers

A confusing fall warbler, autumn 2011 (photo by Steve Gosser)

2 September 2021

The remnants of Hurricane Ida held back bird migration for two days in Pittsburgh but the logjam has broken. Today and tomorrow hold the promise of many migrating birds in southwestern Pennsylvania including mixed flocks of confusing fall warblers. Here’s a tip on how to identify them. This even works hours later at home with your reference guides.

In the field with a hard-to-identify bird, write down every feature you see as if you were going to draw the bird. Don’t forget habitat and behavior.

Details, details, details! The more details the better. If you get only a fleeting glimpse describe whatever jumps out at you.

The details will be useful when you get home and look at field guides.

Let’s try it on this bird.

At first glance (squint your eyes to see less):

  • perched in a tree
  • smaller than a sparrow; warbler size
  • charcoal gray back
  • yellow chest
  • white wing bars
  • plain face
  • (Under the Tail is important too but we can’t see it here.)

More details:

  • yellow chest has pale gray necklace with stripes

Even more details:

  • broken eye ring
  • throat above necklace is yellow
  • some stripes on flanks
  • greenish patch on back
  • maybe a white patch on topside of the tail

Tools: The Warbler Guide by Tom Stephenson and Scott Whittle has free downloadable tools that show all the warblers side by side. Get them here: QuickFinder PDF (my favorite) or QuickFinder JPGs.

Practice! Use this technique in the field. See how I used it to identify another confusing fall warbler: Orange Crowned or Simply Yellow.

So what bird is pictured above?

Leave a comment with your answer and — most important! — the details that led you to that conclusion.

UPDATE, 3 Sept 2021, the answer is: Magnolia warbler

(photo by Steve Gosser)

Birds’ Inner Ears Can Recover Lost Hearing

American robin, watching and listening (photo by Joel Kluger via Flickr Creative Commons license)

12 August 2021

On Monday when I wrote about the handsome trig (red-headed bush cricket) that sings loudly at 7000 Hertz, I mentioned that upper range hearing loss prevents me from hearing him. Hearing aids help a little but nothing can fix it. My hearing will never return to its youthful ability.

Birds don’t have this problem. If the loss is in their inner ear, their bodies repair the damage. Learn more in this vintage article: Birds Can Recover Lost Hearing.

Perhaps birds can recover their hearing because their lives depend on it. Gene Henderson reminded me of a high-pitched danger call that American robins make. At 7200 to 8400 Hertz it’s now outside my hearing range. Can you hear the four calls in the recording below at 2,5,8 and 11 seconds? They look like checkmarks on the sonogram.

American robin danger call (recording by Kate St. John)

(photo by Joel Kluger on Flickr, recording by Kate St. John)

What Sex Is This Bird?

What sex is this hummingbird? (photo from Wikimedia Commonss)

6 August 2021

In late summer in eastern North America a different looking ruby-throated hummingbird (Archilochus colubris) shows up. If you don’t look closely you may misidentify it.

It doesn’t look exactly like an adult, pictured below, but it resembles the female.

Adult male and female ruby-throated hummingbirds (photos from Wikimedia Commons)

So is it female? No!

See the red dots on the throat? It’s a young male, born this spring, who is already developing his red gorget.

Before he has red dots you can still identify him by the stippling (dotted lines) on his throat. This young male, below, has stippling without red dots.

Juvenile male ruby-throated hummingbird (photo from Wikimedia Commons)

Unfortunately the bird pictured at top was misidentified as female on Wikimedia Commons. I corrected the description but cannot change the filename that contains the word “female” so he will still confuse people.

Proving that you should not believe everything you see on the Internet.

For detailed tips on identifying young ruby-throated hummingbirds, see this article at The Spruce: Ruby-throated Hummingbird Identification.

(photos from Wikimedia Commons; click on the captions to see the originals)

I Don’t Look Like My Parents

Juvenile chipping sparrow (photo by Marcy Cunkelman)

8 July 2021

Summer is a challenging time to identify birds when fledglings look quite different from adults. Here are seven species whose babies can honestly say, “I don’t look like my parents.”

American robin adults (left) have plain rust-colored breasts. Juveniles (right) have spotted breasts.

American robin: adult and fledgling (photos by Steve Gosser and Charity Kheshgi)

The differences between juvenile and adult downy woodpeckers are subtle. Juveniles (left) have a faint red patch on top of the head while adult males (right) have a vibrant splash of red on the back of the head. (Don’t be fooled by the red flower behind the male in this photo.)

Juvenile downy woodpecker (left) being fed by father (photo by Marcy Cunkelman)

Red-bellied woodpecker juveniles (middle photo) are very plain with no red on their heads. Adult males (left) are red from bill to nape while adult females (right) have red napes, pale foreheads, and a spot of red at the bill.

Red-bellied woodpeckers: adult male, juvenile, adult female (photos by Marcy Cunkelman and Cris Hamilton)

In breeding plumage adult European starlings (left) are iridescent glossy black while fledglings are dull brown (right). Check out the shape of the fledgling’s beak and how he opens it. He has that in common with his parents.

Adult and juvenile European starlings (photos by Chuck Tague and Charity Kheshgi)

Juvenile northern cardinals (dark bird on branch) resemble their mothers but the juveniles have dark beaks. Their mothers (at right) have orange beaks.

Northern cardinal: Adult male feeding juvenile, female has orange beak (photos by Bob Kroeger, Cris Hamilton)

Juvenile brown-headed cowbirds never look like their foster parents. These dull brown, chunky birds have short, fat necks and “fat” beaks. The beak is the clue.

Brown-headed cowbird chick begging from song sparrow host (photo from Wikimedia Commons)

And finally, young chipping sparrows look so different from their parents that you’d think they’re another species. The juveniles are stripey brown (photo at top) while their parents have plain pale breasts and rusty caps. The best way to identify a fledgling chipping sparrow is to watch who it begs from.

Adult chipping sparrow tries to ignore its begging youngster (photo by Marcy Cunkelman)

A Hat Tip for this topic goes to Mary Ann Pike who described it in a comment yesterday.

Did you find any fledglings hard to identify this year? Let me know in a comment.

(photos by Marcy Cunkelman, Steve Gosser, Charity Kheshgi, Cris Hamilton, Bob Kroeger, Wikimedia Commons)

Mallards in Eclipse

Male mallard in eclipse plumage, Colorado, July 2016 (photo from Wikimedia Commons)

7 July 2021

In the middle of summer the male ducks disappear — or so it seems. The males are still present but they look like females because they’ve molted into eclipse plumage.

Let’s take a look at mallards to see how this works.

Mallards (Anas platyrhynchos) replace all their feathers once a year but males and females do it at different times. Females molt while nesting (February–May); males molt after the breeding season (June–August).

The molt begins with a complete loss of remiges (wing flight feathers) that takes only a few days, rendering the bird flightless for 3-4 weeks. Fortunately males simultaneously replace their brightly colored body feathers with dull ones so they can hide in dense marshes. Eclipse plumage keeps them out of danger.

Here’s the transformation.

Male mallard gradually changing into eclipse plumage (photo from Wikimedia Commons)

Notice that the male’s head becomes mottled green (below) and then dull brown (photo at top).

Male mallard, head color is changing during molt (photo from Wikimedia Commns)

Once the males have made this transition it’s a challenge to tell them apart from females but here’s a clue. Look at their bills. In the summer males have yellow or greenish-yellow bills while females have dull orange-ish bills.

Mallards bills: male in eclipse, female in summer (photos from Wikimedia Commons)

Eventually the male starts to molt back to his typical plumage. Partway there he looks like this.

Male mallard in eclipse in Illinois (photo from Wikimedia Commons)

And by November he’s back to his normal flashy self in time to court his springtime mate.

Male mallard in spring plumage including the curly tail (photo from Wikimedia Commons)

This summer when you see a mallard, look at the bill. Maybe he’s a male in eclipse.

(photos from Wikimedia Commons; click on the captions to see the originals)