Monday, June 29, 2020

Why do bird beaks have so many different shapes?

There are so many different types of beaks on birds. Why?

The different size and shapes of bird beaks, or bills, helps each bird species feed on different foods. Birds also use their bills as tools to hold and manipulate items as they don't have hands.

Below I have photos of birds and have designed a playful guessing game for you. I show you the bill of various birds and ask you to say what kind of household tools the bill reminds you of. Plus, at the end, I have a bonus photo that's really hard! Can you guess it?

Bird "hands" (their wing tips) are covered with feathers and lack fingers. Well, technically, birds have bones equivalent to a thumb and two fingers, but they are fused together into the wing bones. At your next barbeque with chicken wings, look at the outer pointed part covered in skin and no meat. That's the finger part. Be warned, though, that someone's going to tell you to "Stop playing with your food!" You could tell them that it is for science. But that reasoning might not always work.

Bill and beak are interchangeable terms. Beak is often used for shorter, curved, bills. Thus, bill is more all-encompassing. I will use the term "bill" for the most part. It is equivalent to our mouth, jaws, teeth (modern birds do not have teeth, though some prehistoric birds did have teeth). The nostrils of birds are set in the bill, too.

Bills are used for eating. Birds grasp food with the bill, whether animal or vegetable. Most birds swallow their food whole. Hawks will tear larger prey apart. Sparrows can move their bills (jaws) in a circular chewing motion that helps them remove the hulls from sunflower seeds to reach the meaty kernel inside.

Birds also use their bills for preening, like a comb to clean and straighten their feathers.

Birds also use their bills for singing, fighting, courtship, feeding young, building their nests. Let's see, what else? Delivering babies? Okay, fairy tale. Sorry to disillusion you. But they do carry out dirty diapers from the nest in the form of fecal sacs of the nestlings. Gulls carry clams up in the air and drop them on streets to break them open for food. I'm sure I'll think of more things as I continue with the photos below.

First, though, this image...

Image of tools and kitchen utensils

So, what do all these tools and kitchen utensils have to do with bird beaks? Everything!

Each kitchen utensil grabs and holds a different type of food. The spoon scoops up broth as a duck scoops up plants from the water. Lamellae act as a sieve on the bill of swans as a slotted spoon. I show a pliers because I didn't have a nutcracker to represent the seed eating bills of sparrows. I could have used a corkscrew, chisel, tweezers, and baster to represent other bill types. Perhaps you can think of others once you see the photos and examples below. All photos are by the author (that's me!), Greg Gillson.

This is going to be fun--let's play "name that bill" and similar kitchen utensil or tool! How many can you guess?

Photo of Northern Shoveler
Northern Shoveler
1) To get started we'll go with something easy. This duck is called a Northern Shoveler. It has a broad flat end to the bill. It swims forward through with its bill down in the water straining out tiny plants and water insects.

What kind of tool or utensil does this duck's bill remind you of? If you say a shovel, well you're wrong! Okay, no you're not. But a spoon is a good choice too! Did you think of spatula?

Photo of Long-billed Dowitcher
Long-billed Dowitcher
2) Long-billed Dowitchers grab worms and other invertebrates out of the mud with their very long and straight bills. What kitchen utensil does this remind you of? Yes, a straight tongs!

Many other shorebirds have straight bills like this, some long, some shorter. Examples include Wilson's Snipes and Willets.

Photo of a Great Blue Heron
Great Blue Heron
3) Great Blue Herons also have a long straight bill. Long means that the bill is longer than the head. Straight means the commissure is straight. Commissure, let's see, that's defined as the line along which the upper and lower bill halves (mandibles) close. Added bonus: I get to throw in some vocabulary words for you!

What tool or utensil does this bill remind you of? Well, herons stab their food, then toss the fish or mouse or frog or snake into the air and swallow it head first! So that bill is a dagger or spear tip!

You probably don't have many spear tips in your kitchen drawers, though. On second thought, we did when I was growing up. Well, in the garage. We lived in Minnesota and my father would do spear fishing on the ice in winter. Sometimes with a bow and arrow! Now I've really digressed, haven't I? But use your imagination for this game!

Other birds with dagger-like straight bills include egrets, loons, bitterns, kingfishers and terns.

Photo of Long-billed Curlew
Long-billed Curlew
4) All long bills are not straight, as this Long-billed Curlew shows. This is definitely a curved set of tongs! When the bill curves down like this it is called decurved. But no bills curve up, though, right? Well, just you wait and see!

This bird feeds for worms and crabs on sandy shores. Does it stick that whole bill in the sand? No. It can feed straight down in deeper water. But often the bird bends down and holds its head sideways into the sand or mud shallowly.

Other shorebirds like this curlew have long curved bills. The tree gleaning Brown Creeper has a fairly long decurved bill too, for getting insects out of deep bark crevices.

Photo of American Avocet
American Avocet
5) It turns out their are several birds whose long bill does curve up. This is called recurved. This American Avocet just plucked some creature out of the water and you can see it half way up the bill on the way to being swallowed. This is just the other side of the curved kitchen tongs.

Other birds with recurved bills include godwits and stilts. It is a pretty rare bill type, though.

Photo of Evening Grosbeak eating sunflower seeds
Evening Grosbeak
6) Seed-eating birds like the Evening Grosbeak above have heavy conical (shaped like a cone) bills. They crack open seeds, grains, and nuts to reach the edible kernel inside. Do you see that this is also a short bill, shorter than the head?

What household tools do you use that is similar to the bill of the grosbeak? Well, a nutcracker or pliers come to my mind!

Such birds may glean seeds on the ground or from trees. Bills can be huge, like the grosbeak, to crack open larger seeds. Conical bills can be more dainty for gathering weeds seeds or picking seeds from the ground, like goldfinches and juncos.

Other birds with seed-eating bills include finches, sparrows, towhees, buntings.

Photo of Gila Woodpecker
Gila Woodpecker
7) What kind of bill does this Gila Woodpecker have? This is easy! Woodpeckers have chisel-shaped bills to excavate their nest holes and find wood-boring insects to eat.

Nuthatches also have chisel-shaped bills. Yet not all woodpeckers bore into trees for insects. Flickers eat ants on the ground. Sapsuckers drill very shallow depressions in the bark and come back later. There they find sap and insects stuck in it to eat. Three-toed Woodpeckers flake bark off certain pines or scour recently burned trees to find bugs in softer wood.

Photo of Black Oystercatchers on the rocks
Black Oystercatcher
8) Well, the name Black Oystercatcher gives away the food these birds of rocky shores eat. Besides oysters they eat other mollusks, including snails, clams, mussels, and limpets. How do these birds get the clams open? They insert their very tall, but thin bills and snip away the muscle at the hinge of these bivalves.

What tool do these bills act like? Well, there is a knife designed after the the bill of the oystercatcher. It is called an oyster shucking knife! The two halves of the shells then fall open. But to get them off the rocks they use their bills as scissors to cut or as a pry bar to remove them.

Photo of Rufous Hummingbird at feeder
Rufous Hummingbird
9) The unique bill profile of this Rufous Hummingbird is long and round.

This may remind you of a straw or syringe. Really, though, these birds don't suck up liquids. Instead, they reach into long flowers and extract the nectar with the brushy tips of their tongues! It's more like one of those claw grabber tools that mechanics use to reach nuts and bolts they have dropped in the engine compartment.

In many ways, the long thin sticky tongue is shared by woodpeckers.

Photo of Yellow Warbler
Yellow Warbler
10) The Yellow Warbler uses its thin pointed bill to pick up little caterpillars and insects it gleans in from tree leaves.

What tool is this bill? It is a little tweezers!

Besides warblers, some of the small sandpipers have short thin bills used to pick food from the surface rather than probe deeply under the surface.

But wait! There's more!

Photo of a Black-capped Chickadee

Bonus: Finally, we have this Black-capped Chickadee.

This bill is kind of short and stout. It's not a tweezers or a pliers. It doesn't seem to be specialized at all. It is a very generic bill.

Do you know of a generic eating utensil? It's not a spoon. It's not a fork. What is it? It is a cross between the two. It is those plastic "sporks" you get at the drive-thru restaurants!

Actually, many birds have generic bills. Some longer, some shorter, some more like tongs, some more like pliers or tweezers. Jays, robins, doves, coot, vireos, blackbirds all have bills that are more generic.

This isn't all the possible shapes of bird bills. Here is a longer list of some more (but not all) bill characteristics:

Acute: Coming to a sharp point, like the Yellow Warbler above.

Bent: The bill of flamingos have a sharp bend in them.

Chisel: A bill with a beveled tip as woodpeckers.

Compressed: A bill higher than wide, like a puffin.

Conical: Shaped like a geometric cone, such as a sparrow.

Crossed: Easy! This is the crossed bill of the crossbills!

Decurved: That's curved down, like curlews.

Depressed: Not the sad depressed. But meaning wider than high; flattened, like a duck or goose.

Gibbous: Bills with big bump on them like a Mute Swan or Surf Scoter.

Hooked: Ooh, we didn't show any birds-of-prey, did we? Or parrots or shrikes, either.

Long: The bill is longer than the rest of the head.

Recurved: That's curved up like stilts and avocets.

Serrate: With saw-like bumps. A steak knife is a tool. A merganser is a duck with those features on the bill, used to hold slippery fish, not fillet them.

Short: The bill is much shorter than the rest of the head.

Spatulate: Spoon-shaped like the ducks.

Stout: High and wide like a chickadee, coot, or chicken.

Swollen: The sides of the bill of tanagers swell out.

Terete: Circular in cross section, like a hummingbird.

Toothed: Not real teeth, but the bill has a tooth-like bump (opposite from a notch), falcons have this.

This has to end, but I keep thinking of more. Have you seen photos of Shoe-billed Storks? Have you seen pelicans with pouches? Hornbills? The variety of bird life and bill shapes alone seems endless. Enjoy!

You may like these related bird anatomy articles:

Why do birds' legs look so funny? Do they bend backwards?

You want to know, but have been afraid to ask: Do birds pee? How do birds have sex?

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