Mallard Duck

     One of the most identifiable (at least the males, or drakes anyways) ducks in the world is the Mallard (Anas platyrynchos). While its natural range is throughout the Northern hemisphere, it can now be found throughout most of the world. It is the most abundant and widespread of all ducks. Except for Muscovy ducks, just about all domestic ducks have the Mallard as their ancestor and that has helped their spread. 
     Mallards are large ducks (about 24" and 3-4 lbs). The adult drakes in winter have an iridescent, glossy green head, though it can appear black to purple depending on how the light hits it. They are commonly called  "Green Heads" due to this trait. They also have a white collar around their necks and curly dark feathers at the base of their tails that are sometimes referred to as drake feathers. Both drakes and hens have a purplish blue patch of feathers on their wings that is bordered in white that is called the speculum. This is distinctive enough to help in distinguishing the females specially from many similar ducks, though it is not always visible.

A pair of Mallards, with the speculum wing patch visible on the hen.

     Their scientific name is derived from the Latin "Anas" for "duck" while their specific name "platyrynchos" comes from the Greek words for "broad beak." This name was initially given to them by Linnaeus himself. They were once simply called "Wild Ducks" in England, while some still refer to the plain brownish hens as "Susies." The word "Mallard" comes to us from Old French for "wild drake." 

A pair of Mallards tipping up to feed. Note the curly drake feathers on the male to the right.

     Mallard are our largest dabbling, or puddle, ducks. This means that they normally feed at the surface, tipping bottoms-up to reach food below. They rarely dive under water, except maybe to escape a predator or if wounded. Dabblers can also spring directly into the air when taking off. Most diving ducks to the contrary need to patter or run along the surface before attaining flight. Here is a short video showing how dabbling ducks typically feed:

                         https://www.youtube.com/watch?v=SKpZdXlXuMk

     Mallards consume mostly plant material. Most of the year, up to 90% of their diet consists of aquatic plants, their seeds, tubers, and grains. I've seen large flocks descend onto corn stubble and soy fields on numerous occasions. But I've also seen them furiously feeding on water fleas and fingernail clams in small vernal pools. They are not too picky, and during certain times, 70% or more of their diet switches to animal matter. This is particularly true of hens prior to nesting when they need all the protein and calcium they can find. I've even seen them hunting wood frogs at these pools and swallowing them whole. Ducklings in particular feed heavily on insects and small invertebrates while growing, before switching to their mostly vegetarian diet.
     Hens always seem to be in short supply. Males display and attempt to pair up with them throughout the winter and into early spring. Mallard drakes are very aggressive in their pursuit of mates, particularly late in the spring season. Any single hen, one abandoned by her mate after starting to lay eggs, or one not defended well by her mate can be pursued, often by a group of males who will gang up on her. This is exasperated in overcrowded situations. Sometimes the drakes injure and on rare occasions even drown hens in their ardor. 
     This aggressive urge for mallard drakes to mate is not limited to just Mallards. Hybrids are not uncommon, and sometimes these result from forced copulation with other duck species. There are even stories of domestic mallards with out enough females attempting to mate with chickens and even drowning them. Mallards are not that picky therefore about mates and several hybrid duck species are sometimes seen. These include Mallards crossing with Pintails, Gadwalls (what Audubon called a Brewer's Duck), Widgeon (both American and Eurasian), Shovelers, Green-winged Teal, Cinnamon Teal, Eurasian Teal, and domestic ducks.

A hybrid Mallard mix, likely with a domestic duck.

     With some duck species that are rare or have isolated populations, there is some concern that Mallards may swamp out the less populated species, perhaps even leading to their extinction. This is suspected to be the case in such species as hybrid American Black Ducks, Mottled Ducks, Mexican Ducks, and Hawaiian Mottled Ducks. In some parts of the world, Mallards are considered invasive, threatening to out-breed local species. This is the case with Africa's Yellow-billed and Meller's Ducks, Pacific Black Ducks, and Asian Spot-billed Ducks.

A Mallard-American Black Duck hybrid.

     Mallards, perhaps helped due to their escape and release from captivity, are the most adaptable of ducks and have moved into habitats that once were the niche for other duck species. They have benefited in many ways from people and are much less picky about nesting locations or proximity with people than other ducks. It is illegal in some areas to release or even keep Mallards. Feral ducks or those fed by people may not migrate, and if they mate, may pass that trait on as well. They have the most extensive breeding range of any North American duck and will nest the first year after being born. Mallards have been expanding their breeding range since the early 1900's, and some suspect at the expense of other duck types. 

A Mallard drake among three Mallard hens: one pure bred, one mixed with Black Duck, and one with domestic duck.

     Once a Mallard hen has mated, she chooses a site, usually near water, but up to a mile away, in which to nest. Sometimes they pick very unsuitable sites and you hear about people rescuing ducklings from roofs, garages, and helping them cross busy streets. Hens may even dump their eggs into other ducks' nests (not always Mallards) and have eggs dumped into theirs. Males, as in all our dabbling ducks, do not help raise the young but instead often form small bachelor flocks during the warmer month. 

A Mallard hen leads her brood. One of the ducklings looks to be of mixed heritage.

     If the nesting situation ends up working out, then each hen lays about an egg a day in her ground nest until she reaches her compliment of 8-12 eggs. These can make up more than half her weight, so this is taxing on the mother. She will often sit tight concealing her nest until almost stepped on. This has led to some farmers using "flushing bars" ahead of their mowers and tractors to spook the hens before its too late. Many hens are also caught by predators such as foxes and coyotes while sitting tight. Skunks, raccoons, possums, and many others prey on their eggs as well. 
     If lucky, she incubates her greenish-white eggs for about 28 days before they all hatch. Within hours she leads her precocial ducklings to water. Sixty or so days later they are fledged. If successful, hens often return to nest near where they nested the previous year. 
     Mallards are very vocal and gregarious ducks. The hen in particular quacks quite loudly and often. Drakes do so much less and have a quieter and raspier quack. Mallards are the most hunted of all ducks, responding well to calls, decoys, and considered decent table fare. Their numbers fluctuate yearly, but are considered stable. Duck population and nesting surveys are often based heavily on Mallard numbers before setting hunting seasons and limits. Indeed, they are the most numerous and widespread of North America's ducks. 
     Mallards may be common, but they are so because they are so adaptable. They will overwinter as far North as the food supply and open water allows. In fact, like some other waterfowl, they will sometimes paddle around in small flocks to keep an opening for them to use in the ice. Here is a short video showing one working its way through the ice:

                    https://www.youtube.com/watch?v=0c0DtPPdbGw

     So Mallards are abundant and adaptable survivors. If nothing gets them, they have been known to live as long as 26 years and 4 months (as we have learned from recovered banded waterfowl). They are quite beautiful ducks that have gotten accustomed to and even benefited from humans, much as we have also benefited from these ducks the world over.