English: This is a Mallard duckling (Anas platyrhynchos). This duckling can also be described a hatchling because it had recently hatched. Mallard hatchlings are covered in down, and can eat and swim soon after being hatched. To give this picture scale, the duckling was less than 3 inches (7.6 cm) long when the picture was taken. The light eye stripe indicates this is a female duck. Males tend to have a more pronounced eye stripe. Mallard ducks are extremely adaptable to their environment as omnivores, and can breed with other types of ducks. This has led to criticism of this species of duck. I have personally observed these ducks, including this duckling, at Green Lake in Seattle over many years, and they do provide benefits to several other species, including humans. In nature, there is a concept called, “symbiosis” which means one species provides a benefit to another species. The benefits can be mutual, such as a bird that rides around on the back of a rhinoceros or elephant and eats the flies and ticks the larger animal can not reach. The bird receives a direct benefit from the symbiotic relationship in the form of food and protection while riding the larger animal. Another example, is a bee which receives nectar from a flower and the flower receives a benefit when pollen sticks to the bee’s legs and the pollen is transported to other flowers by the bee. In the case of the Mallards at the lake, I have seen them regularly paddle four abreast past the swimming area grabbing mosquitos and other bugs out of the air. They appear to swim abreast to insure that one of the four gets any insect that might fly a defensive path. I have observed these groups grab more than 20 insects on each pass along a 100 foot section at the swimming area steps in the Spring season. Many other times, I have seen groups of twos and threes paddling with the lead duck churning up algae with aggressive padding and the following ducks eating the algae churned up. This behavior can be analogized to a flock flying in formation with the following ducks benefitting from the energy of the vortex created by the lead duck’s wings. Stationary ducks also regularly pivot forward and reach down under the water with their long necks to bob for algae that is either free floating or stationary, which is sometimes termed, “dabbling”. The benefits humans receive from the symbiotic relationship with Mallards are that the ducks keep the swimming area clear of mosquitos and algae, that might have to be otherwise addressed with insecticides and algae control chemicals. The Mallards benefit because the humans using the swimming area periodically supplement the Mallard’s diet with bits of bread and other handouts. The Mallard’s droppings do enter the lake, but the lake is large, which minimizes the effect. Plus fish and other organisms in the water column quickly break down the droppings. There is some natural predation of the Mallards by a female bald eagle at the lake who has a large nest at the top of one of trees on the North side of the lake near the swimming area. By keeping the water clear of algae, the Mallards allow the bald eagle to see the fish, and once the bald eagle dove on a fish within 30 feet me as I ran on the running trail that skirts the shore. The dive was not like a graceful pluck from a stream in continuous flight, but instead, a big feet-first belly flop, which suggested the fish was at least one foot under the surface. The eagle’s catch would not have been possible if the Mallard ducks did not continuously control the algae in the lake. Luckily, the duckling in the picture survived the eagle and grew to adulthood.