Birds under Water 3 - Intrepid Divers

A series on birds at Halibut Point with diverse adaptations

to finding food below the water surface:

Dabblers, Plungers, Divers, and Pursuers.

Buffleheads, male and female

During the winter season at Halibut Point we enjoy the presence of ducks with the ability to forage for plants and small invertebrate animals on the ocean bottom. They may dive to depths of up to fifty feet. The birds that operate close to shore often find themselves in a zone of extreme turbulence, which adds to the wonder of their success.

The text for this article comes from the sportsmen's organization Ducks Unlimited. *

Bufflehead, diving

The body of a diving duck is much more compact and fusiform (wider in the middle and tapering toward the end) than that of a dabbler. Divers' wings are also more compact, which allows them to be compressed tightly against the body for greater diving efficiency. In addition, divers' legs are set much farther back on their body, and their feet are much larger and have a lobed hind toe. These adaptations help propel the birds while they are underwater.

Bufflehead diving and Harlequin observing

Harlequin Ducks

Harlequin male, diving and female, snorkeling

Diving ducks typically have higher body densities than other waterfowl. Just before they dive, the birds compress their feathers against their body, squeezing out air, which further reduces buoyancy. Next, with a single thrust of their powerful legs and feet, diving ducks arch their bodies upward and dive headlong.

Goldeneye, male and female

Goldeneye diving

Once underwater, the birds use their feet and wings to propel them downward in search of food. They steer during descent largely by shifting their head and tail positions. Once near the bottom, diving ducks use their feet to maintain a hovering position while the birds forage for aquatic insects, small mollusks, seeds, vegetation, roots, tubers, and other food.

Common Eiders

When the dive is complete, diving ducks simply relax their muscles, stop paddling, and ascend to the surface like a cork. Diving ducks that feed on submersed aquatic vegetation or sedentary invertebrates like clams return to the surface in almost the same place.

Common Eider

Harlequin Duck drakes

* The text in this article is taken from "Diving Ducks: Into the Deep," by John M. Coluccy and Heather Shaw, as published on the Ducks Unlimited website www.ducks.org.

Birds under Water 2 - Plungers

A series on birds at Halibut Point with diverse adaptations

to finding food below the water surface:

Dabblers, Plungers, Divers, and Pursuers.

Belted Kingfisher scanning

Other than sharp eyes, a big beak, and a reckless constitution, it doesn't necessarily take much in the way of extraordinary avian equipment to plunge for prey below the water surface. You don't need webbed feet if swimming isn't part of the plan.

Kingfisher rising

You don't even have to be particularly waterproof for a quick strike, but the ability to get back up into the air is essential.

Ring-billed Gull hovering

Most of our larger gulls are too buoyant in the water and heavy-bodied in the air to plunge below the surface as effectively as the Ring-bill.

When small fish appear near the surface this species is capable of going after them.

Migrating juvenile fish driven into the shallows by predators make a perfect opportunity for a moderate plunger.

Minnows schooling near the quarry surface are fair game for Ring-bills. Great Black-backed and Herring Gulls lack the quickness for this technique.

Northern Gannet

Gannets are the most highly adapted of the maritime plungers in our area. They soar high enough to see well below the surface of the ocean.

When striking they tuck into an aerodynamic posture for speed and fine ballistic steering. Just before hitting the surface they tighten into an arrow to penetrate the water to the fish's depth.

Their foreparts are reinforced to withstand impact. Unlike gulls, the design of their legs and feet enables them to chase fish under water.

After a successful dive a gannet may have to swallow his prey quickly at the surface before a gull can arrive to do what gulls do best. Even-handed biologists call the gull's way of making a living kleptoparasitism, a fancy term for stealing, but less invasive than lodging inside and digesting a host's internal organs.

Then the honest predator lifts off the water to fly in search of another meal.

Birds under Water 1 - Dabblers

A series on birds at Halibut Point with diverse adaptations

to finding food below the water surface:

Dabblers, Plungers, Divers, and Pursuers.

Brant in Folly Cove

Considering the abundance of life in the waters of the earth, it should not be surprising that birds have sought out its food potential. 

Brant eating sea lettuce

From their origins as creatures of the land and the air some species have developed anatomy and lifestyles to harvest sustenance from aqueous environments.

Dabbling Mallards

Beyond wading in search for food, a significant variety of birds have enhanced their waterproofing, foot and bill structures to swim on the water surface and reach below in search of food sources.

American Wigeon (top) with a Mallard pair

Mallard ducks are the commonest and emblematic local dabblers. Searching among Mallards may reveal cohabitating species.

Female Mallard with Green-winged Teal

The dabblers are generally found in shallow water. They tend to have a rounder shape and float more buoyantly than waterfowl that rely on diving for food.

Warm Bodies

Colorful barelegged creatures with the gifts of flight and song are surely a great marvel of the winter landscape.

Red-winged Blackbird

Their concerts are not cancelled by irregular weather. To be sure of its melodies Nature must keep songbirds warm.

Tree Swallows during spring snowstorm

Photo courtesy of Keith Williams/Creative Commons

Huddling birds can share their warmth, reduce exposure to cold air, and shield each other from wind.

Brant

The hard work of flight generates more than enough heat for a comfortable body temperature while a bird is active.

Robin

At rest they are likely to fluff their feathers and wrap themselves in their wings as advantageously as possible.

Snowy Owl

Snowy Owls even have feathered feet.

Common Eider

Eiders, one of our winter coastal ducks, have some of the most effective insulation of any bird. Their perfectly interlocked outer feathers form a 'barrel'  to trap pockets of air around their bodies even when diving. The birds waterproof this guard layer by using their bills to coat it with oil from a preening gland near the base of their tails. Eiders are also the source of down feathers utilized in superior winter clothing and bed comforters.

Varieties of feathers

Illustration from The Birdwatcher's Companion by Chris Leahy

Intricate combinations of feather structures beneath the outer layer keep the bird warm as well as streamlined for flight.

Mourning Dove

A few species of birds like egrets, herons and mourning doves grow special feathers that disintegrate into a powder they use to waterproof their feathers.

Black-capped Chickadee

Chickadees weighing less than half an ounce can maintain a daytime body temperature of 100 degrees Fahrenheit by having great insulation, being very active and remembering where they store their food. They eat more than a third of their weight every day. Compared to many other birds, chickadees have a large hippocampus - the part of the brain that’s responsible for spatial memory. In the fall, this part of their brain gets even bigger!

These small creatures can't put on too much bulk for aerodynamic reasons. Instead, they are experts at shivering. Birds activate opposing muscle groups to create contractions without all the familiar trembling that mammals use to generate heat. At night, tucked into a tree cavity, they might reduce their body temperature as much as 22 degrees from their daytime level in a process called regulated hypothermia.

Chickadee foot temperature is regulated near the freezing point and may stay cold most of the time all winter, even as core body temperature stays high. Of course, a bird’s comfort level for foot temperature is likely very different from ours. They would not feel uncomfortable until the point when damage occurs from freezing, if ice crystals were to form.

Online information on Chickadees
1. U. S. Fish & Wildlife Service Newsroom, "How do birds keep warm in the winter?"
2. Audubon.org, "How Do Birds Cope with Cold in Winter?"
3. Cornell Lab All About Birds, "How Do Birds Survive the Winter?"