Anatomy 8 - Upland Gallery of Bills

All birds have unique and versatile bills exactly suited to their lifestyle. This truism makes it possible to sort out and group birds by their bills alone, in a satisfying correlation of form and function. Birds depend on their bills in universal ways as well as for unique specializations. Wear and tear from all these uses is compensated by the constant formation of new keratin, much like our fingernails.

Carolina Wren

Wrens use long, sharp decurved bill to probe for insects in tree bark and litter.

Blue Grosbeak

Grosbeaks are close relatives of finches and sparrows with especially large conical mandibles for crushing and husking seeds.

Red-bellied Woodpecker

Woodpeckers use their beveled, chisel-shaped bills to excavate tree wood in foraging for food and in cavity nest-building.

Green Heron

The Green Heron's long pointed bill is equally adapted to snatching or spearing fish.

Cooper's Hawk

A hooked bill bending at the tip into a sharp point enables raptors to grasp and tear apart their prey.

Red Crossbill

Crossbills live primarily in coniferous forests where their flattened, bypassing mandibles efficiently extract seeds from pine and spruce cones.

Phoebe

Eastern Kingbird

Aerial insectivores (including swallows) tend to have wide flattened mouths surrounded by bristly feathers that increase the area of their 'scoop'. Flycatchers' bills bear a distinctive hook at the tip.

Mallard

Dabbling ducks, as well as geese and swans, strain vegetation from the water with broad mandibles ridged on the inside. Many have a sharp-edged tip on their bills called a 'nail' for cropping plants.

Black-capped Chickadee with tree pulp

Barn Swallow carrying mud

Eastern Kingbird with nest-lining material

Tree Swallow arriving with grass stalks for weaving

Birds use their bills adeptly, like our fingers, in preparing their nests.

Baltimore Oriole

The consummate weaver at Halibut Point suspends its nesting pouch beneath the tree canopy.

Anatomy 7 - Shoreline Gallery of Bills

 

Illustration by Ralph Scott

"Getting along between the Tides"

North Shore Magazine, September 3, 1977

My eyes were first opened to the subtle distinctions among birds' bills in an article by local master naturalist Ralph Scott. The question he pondered was, "How could so many species feed in harmony in the same small intertidal space?" His answer lay in the various species' physical adaptations to the environment, a matter of anatomy as well as behavior.

Greater Yellowlegs

Over time I've seen all his illustrated species in or around Halibut Point, though it's not their usual habitat. The Greater Yellowlegs has a long recurved bill (curving slightly upwards) typically useful for deep probing in mud flats, so it doesn't usually frequent our rocky shore. This photo shows a sandy spot at very low tide in Folly Cove.

Black-bellied Plover

The stout bill of the Black-bellied Plover enables it to push aside pebbles in search for mollusks and crustaceans.

Semi-palmated Plover

The delicately proportioned Semi-palmated Plover forages for tiny prey with its little sticker bill as the waters recede along the shoreline.

Least Sandpipers

Least Sandpipers are adept at probing within fissures and barnacle masses with their needle-like decurved bills for small invertebrates waiting out the return of the tidal protection.

White-winged Scoter

Many of our maritime diving ducks have stout bills for prying mollusks and crustaceans from the ocean bottom.

Razorbills

The bills of some of the alcids, like Puffins and Razorbills, are flattened on both sides. a peculiarity that evidently helps them in bringing a number of small fish to the surface.

Red-breasted Merganser

One of our premier fishing ducks has teeth-like serrations along its mandibles to grasp slippery prey.

King Eider

The most beautiful, bizarre, and desirable of local shoreline sights comes in a rare winter encounter with a male King Eider. The frontal shield of its bill is largely made up of fat. Otherwise it is constructed like the scoters for prying loose such prizes as mussels and crabs.

Anatomy 6 - Wings

One preconception I've had to fly from is the idea that birds paddle themselves aloft on fixed wings that somehow get them places by vigorous flapping up and down.

Eastern Mockingbird

Just as we had to see past the tempting simplicity that the earth is flat, so too do we marvel at the curving intricacies of wing strokes with many parts performing dynamically and interdependently at the will of the bird.

Blue Jay

For one thing, birds fly not so much by pushing air down to the rear as by stroking forward to take advantage of lift coming from air passing over the curved upper surfaces of the wings.

Great Egret, Folly Cove

With its huge wings and light body this egret rises effortlessly by stretching its wings out to the breeze.

Turkey Vulture, perched on grout pile

That's why heavier birds like to land on a promontory where air currents are available to help them take off again.

Turkey Vulture rising

They fall off into space, allowing the passing air to create lift, and slowly flap away.

Black Vulture

Soaring birds take advantage of the energy of rising air thermals and guidance control from individually operated feathers. Buteos, the broad-winged class of hawks and eagles, hunt in this way, often from great heights.

Cooper's Hawk

The accipiter class of hawks with narrower wings and long tails are more apt to hunt from a perch, pursuing prey with powerful wing strokes and maneuverability through woodlands.

Sanderlings

The characteristically long narrow wings of shorebirds give them the ability to react quickly to breaking waves, and to fly in tight flock formations.

Northern Gannets

High aspect ratios - measured by dividing a wing's length by its breadth - equip some seabirds to glide long distances without flapping and fly actually into strong winds by dynamic soaring, a flight method well worth looking up as a natural wonder initially counter-intuitive, eventually a wonder-inducing harnessing of everyday physics.

A female Ruby-throated Hummingbird hovering

Of course the ultimate bender of physical limits is the hummingbird which can fly with its body in a vertical position by shifting its wings and consuming a high-energy diet. Every detail of its flight effort coordinates an anatomy unique in the animal world.

Anatomy 5 - Feet

Most of the muscle mass of a bird is in close to its core for reasons of aerodynamics, self-protection and warmth. The bulk of its leg is normally invisible to us beneath feathers. The foot emerges into sight at the ankle, a backward-bending joint, like ours, that we could easily mistake for its knee because of its location high up on the leg. From there the toes fan out in many versatile configurations that adapt the bird to its lifestyle.

Ruby-throated Hummingbird

Most birds we encounter away from the shore use their feet for perching and walking. Hummingbirds, on the other hand, spend much of their time and energy hovering. Their physique emphasizes wing muscles over legs. Their feet are notably small.

Brown Creeper

The relatively large feet of another tiny bird suit it for clambering up and down tree trunks in search of insects. Brown Creepers depend on their long, strongly curved rear claws to help with stability and maneuverability. Their legs are much more developed than hummingbirds.

Turkey

At the upper size limit of Halibut Point birds are turkeys that browse on the ground. They have to be wary and able to outrun foxes and coyotes. Turkeys are very fast, but those hefty leg muscles built up from foraging and running make them a prize catch for carnivores, hunters, and domesticated poultry producers. Partly in compensation for this vulnerability turkeys have developed  sharp, bony spurs on their heel that they deploy in aerial attacks against rivals and in self defense.

Downy Woodpecker

The upland birds in our realm almost exclusively have four toes, three pointed forward, one to the rear. Woodpeckers have found an evolutionary advantage in developing a two-forward, two backward combination for anchoring to a tree. Chimney swifts have shifted all four claws to the front to facilitate hanging at rest inside their roost.

Semipalmated Plover

The water's edge offers the greatest variety of foot adaptations. Semipalmated means partially webbed which improves this plover's traction on slippery rocks and quite possibly its 'swimming' movements through shallow water.

Red-necked Grebe

Grebes are able to work their lobed toes as independent paddles for both propulsion and steering in the pursuit of fish. They can twist their foot 90˚ on the forward stroke to minimize drag through the water.

Double-breasted Cormorants

Cormorants are one of the few birds with webbing extending to all four toes. Coupled with their enormous feet they can reach and accelerate quickly in submarine depths.

Mallards

Ducks of all sorts, being dabblers or shallow divers, manage well with webbing limited to the three forward-pointing toes. For an explanation on their ability to stand comfortably on ice, see my previous posting Cold Feet.

Snow Bunting

Another approach to avoiding heat loss through the feet is to bundle up, as this cool-weather visitor to Halibut Point does with tufts of feathers all the way to its toes. Snowy Owls have developed this protection even further.

Peregrine Falcon

The aerial hunters known as raptors all have large feet capable of tremendous crushing force and piercing claws.

Great Blue Heron

Herons have large feet with very little clenching power, to support then on marshy conditions.

Their long toes radiate like spokes on a wheel.

Black-crowned Night Heron

Certainly there is not 'one size fits all' with wading birds. The arrangement‒ and uneven length ‒  of toes on the Black-crowned Night Heron, which often hunts from a perch, gives a compromise solution to its niche at the water's edge.

Oystercatcher

Oystercatchers, with only three toes, occasionally visit our shoreline, showing one of their particular adaptations to foraging on rocky beaches.

Noticing birds' diverse feet is another way to marvel at nature's ongoing adaptations to opportunity.

Anatomy Study Break - Squirrel Olympics

In the midst of these recent feature stories on the makeup of birds we can divert for a bit into awe and hilarity with Mark Ruber who produced a YouTube on his contest with squirrels raiding his daughter's bird feeder. 

Squirrels flying through the treetops come as close as any mammal can to the high-speed aerial agility of birds. What they lack in wings they surpass with puzzle-solving skills and fearlessness.

Mark began to learn about the well-endowed adversary he was up against when he bought a series of supposedly squirrel-proof feeders.

His investments were systematically plundered by crafty, athletic squirrels. He got to know and name the four marauders in 'his' yard.

Mark is a former NASA engineer with a garage workshop and a zany sense of humor. He and his buddy decided to make life tough for the squirrels and find out what feats they were really capable of. His wife made them promise not to hurt anybody.

Ever the scientist, he set up a nut buffet to determine their favorite food ‒ and bait. They preferred walnuts in every trial.

At the end of an obstacle course testing their intelligence, stamina and grit he constructed a squirrel's dream.

Each station in the course got progressively harder: The Bridge of Instability, The Maze of a Thousand Corridors, The Pitchfork Tumblers of Treachery, The Homewrecker, The Slinky Bridge of Deception, The Tourist Trap, The Quad Steps of Grid Elevation, and The Orbital Assist Platform. 

Mark videotaped the awesome heroics and shenanigans from a blind, like the big-time sports programs do. He analyzed them in slow motion. 

Pointing to the walnut stash Mark said, "If they make it here they've earned the right to gorge next to the birds for as long as they want." By the end of the week all the squirrels could do the full course in 40 seconds. There were winners in every direction--you, me, him, and the squirrel.

Flying squirrel

Now, back to anatomy class. Mark discovered that catapulted squirrels always land on their feet. He concluded they can survive a fall from any height by spreading their limbs like a parachute, lowering their terminal velocity, then extending their arms and legs as shock-absorbers. 

They instantly know where they intend to land. Mark calculated that within 300 milliseconds the squirrel fixes its eyes on that spot and keeps its head locked on target the whole way down through twists, turns and tumbles.

Its second trick in flight control makes a NASA man marvel. When the squirrel wants to keep his upper body from rotating he puts his arms and legs out. When it tucks them in, its body spins, a technique that figure skaters and ballerinas delight us with. Mark calls it straight up conservation of angular momentum.

At Halibut Point we witness our own squirrel performances in the treetops.

Red squirrel

It might not be as much fun as matching wits with them experimentally at the bird feeder, but these critters generally spark up a walk in the Park.