The animal on the cover of SDN: Software Defined Networks is the goosander duck (Mergus merganser), also known as the common merganser. These large ducks can be found in rivers and lakes across Europe, Asia, and North America, near forested habitat.

These birds are nicknamed “sawbills” for the serrations on their beaks that help them grip fish, their primary source of food. They will also eat mollusks, crustaceans, amphibians, and other aquatic prey. Their usual hunting technique is to drift some distance on the water and then fish their way back upstream, diving repeatedly along the way. They are powerful swimmers, and find most of their food by sight.

Male and female goosanders have different plumage; the male is white with a dark green iridescent head and back, while females are a more subdued gray with a reddish-brown head. They prefer to build nests in tree cavities, but will also use nest boxes or rock crevices, depending on their surroundings. In early spring, the female lays 9–12 eggs, which she incubates for about a month. Within a day or two of hatching, the ducklings head for the water and soon learn to feed themselves with fish larvae and insects.

These ducks are social and live in small groups—in the winter, they occasionally come together in “floating flocks” of several thousand. Each goosander eats an average of 10–20 ounces of fish a day, which can cause conflicts with the commercial fishing industry.

The cover image is from Riverside Natural History. The cover ...

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