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Ducks are one of the most recognizable bird families in the world thanks to their funky webbed feet, colorful plumage and big bills. The family is expansive, and Iowa alone is habitat for about 25 duck species every year.
You Looking at Me?
Like many prey animals, ducks have eyes on the sides of their heads rather than facing forward. This lets them spot threats from any direction very quickly, but each eye always looks at different things. Because of this, ducks must control each eye independently in order to perceive depth, or how far away objects are. They do this very efficiently by controlling the curvature of both their lenses and corneas (outermost surface of the eye), which allows them to make adjustments for seeing in both air and water. Humans only control their eyes’ lenses.
Ducks can also see more sharply in a wider range of colors than humans because of a few adaptations of their retinas (back interior surface of the eye). There, ducks have more types of cone cells, allowing them to see into the ultraviolet spectrum, and no blood vessels, allowing for a higher density of sensory cells and thus a clearer image. Instead, they supply blood to the eye with a small, pleated tissue projection called the pecten oculi, which looks a bit like the slats on a vent.
Despite spending lots of time in icy water, ducks don’t get frostbitten feet in winter. They avoid it in part by having minimal muscles in their feet, which decreases the need for blood supply to that area, but the feet do still need some blood to function. So, in the duck’s legs, small blood vessels carrying warm blood going to the foot come in very close contact with similar vessels carrying the cold blood coming back from the foot. Because the temperature difference is so great across that small distance, most of the warm blood’s heat is lost to warming the blood going back into the duck’s body, and not the icy water the foot comes in contact with. Thus, the duck’s foot is cold, but never freezing, and the duck doesn’t waste much body heat. The duck doesn’t mind its feet being cold either, because it has nerves less sensitive to heat and cold than those of humans.
Some duck species, notably mallards and wood ducks, are very aggressive breeders. This can be upsetting to people if they witness a group of overly-amorous males ganging up on one female, but most of the time she’s fine—male and female ducks’ reproductive systems have been developing surprising twists in a sort of arms race for generations. This evolutionary process likely started because there are proportionally fewer females than males in the population, and the male’s genetic success is based on getting at least one of those females to bear his offspring, if not more. On the other hand, the female can only have one or two broods of chicks a year, so she wants to make sure they have high-quality paternal genes and therefore a better chance at surviving and passing on her genes.
This becomes problematic when males of an aggressively breeding species target females of a less aggressive species. The hybrid offspring of such a pair is often infertile or has trouble recognizing and attracting appropriate potential mates the following season, resulting in the decline of the less aggressive duck species. Such is the case of the declining American black duck, whose hens look and sound very similar to mallard hens.
While ducks can be very colorful and attractive, they don’t preen out of vanity. Like many birds, ducks have an oil gland near their tail, and they distribute its oil through their feathers using their beak. This oil helps keep discourage parasites and keep feathers waterproof, so ducks reapply it regularly.
Ducks also preen to clean and realign the tiny criss-crossing filaments that hold their feathers together. This not only makes them more attractive to potential mates, but keeps feathers in prime condition and position for flying.
In addition to cleaning, most ducks replace their feathers twice a year in a process called molting. Shortly after nesting, males and females change out all their feathers, including flight feathers, which can be very dangerous as it prevents their primary mode of escape. In addition, males go from their bright breeding plumage to a more muted, safer color palette, in what’s called an eclipse molt. While females generally carry on as usual during molting, during the eclipse molt males band together until they can fly again.
Depending on the species, males and females will molt again in late fall or early spring, when the males switch back to breeding plumage.
Within the duck family, there are three major subgroups. Sea ducks, including mergansers, scoters, goldeneyes, ruddy ducks and buffleheads, tend to live at sea and visit freshwater for the breeding season. The other two groups, dabblers and divers, tend to live in freshwater environments year-round. Both dabblers and divers are common across Iowa, although dabbling ducks are generally more widespread and diving ducks are found in higher concentrations.
Dabblers are wide-billed, large-winged ducks like mallards, wood ducks, wigeons and teal that live and feed in shallow water. Their wide bills make dabbling ducks adept at filter feeding on algae and floating plants, and these birds can often be seen feeding bottoms-up.
Diving ducks prefer deeper, more open water, and will completely submerge themselves while diving to find food like rooted plants and crustaceans. Their bills are smaller, better adapted to digging for food, and their wings are more compact for better propulsion and decreased resistance while swimming.
Another difference between dabbling and diving ducks is the position of their legs. Dabbling ducks’ legs are much closer to the center of their body, which makes them good at general paddling, walking on land, and jumping into the air. Diving ducks’ legs are situated further back. This is great for swimming, but this makes walking on land much more difficult. It also prevents divers from launching or springing smoothly into flight like a dabbling duck, so they get a running start across the surface of the water like a goose.
When a mother duck is ready to lay her eggs, she lays one a day until the whole clutch is in the nest, and then begins the month-long incubation process. The eggs laid first are not at a disadvantage—they remain completely viable for a few weeks with no care, and the developmental process doesn’t start until triggered by the mother’s body heat. Starting all the eggs’ incubation at the same time helps them all hatch at the same time.
The whole hatching process usually takes about a day, and the next morning the mother leads her ducklings on a walk to the nearest body of water. For tree-nesting species like wood ducks, the flightless ducklings must first leap to the ground, but due to their small size and light weight this is not terribly perilous. Most of them simply bounce on impact, find their feet and waddle away unharmed.
Many species of ducks, including wood ducks and mergansers, engage in egg dumping, where a female lays her eggs in the nest of another hen of her same species. Often the parasitized hen simply takes on the extra eggs and raises them as her own, sometimes laying a smaller clutch to compensate. In terms of evolution, this is advantageous because it allows the parasite mother to lay more eggs than she could care for alone, and the chicks are generally well cared for by the other mothers. Usually these other mothers are not overly burdened either, as a single hen can care for approximately 20 eggs and most only lay a dozen. However, sometimes a nest may be filled with more than 30 eggs, and at this point the surrogate mother either abandons the nest or attempts to hatch all the eggs with decreased success.
Despite popular traditions, it’s unhealthy for people to feed ducks bread. This carbohydrate-laden handout can lead to malnutrition as ducks become less motivated to pursue the aquatic plants and invertebrates they would normally eat, and can even hamper the growth and development of ducklings. In severe cases, young ducks may become so malnourished that they develop an incurable condition called angel wing, which renders them unable to fly. To make matters worse, regular feedings will likely attract more birds, who then are in closer contact with one another and more likely to be aggressive, as well as more likely to pass diseases. Eating moldy bread can also lead to a severe, tuberculosis-like lung infection called aspergillosis, which can wipe out whole flocks of birds.
If you must feed the ducks, consider a moderate amount of something with more nutritional value like defrosted frozen corn kernels, defrosted peas, lettuce, halved grapes, birdseed or earthworms. Be sure not to feed them anything moldy.
In 2002, a year-long study from the United Kingdom found ducks to be the funniest animal. Along with modern cultural references like Daffy Duck and Donald Duck, ducks were found to be silly characters in the fictional stories of many cultures, perhaps because of their physical appearance and waddle. The researcher also noted that the word for “duck” is inherently funny in multiple languages, and other studies have found the hard “K” sound to be the funniest sound in the English language.
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