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Common merganser
The common merganser or goosander (Mergus merganser) is a large sea duck of rivers and lakes in forested areas of Europe, Asia, and North America. The common merganser eats mainly fish. It nests in holes in trees. The name "common merganser" is used in North America, while "goosander" is used in Eurasia.
The first formal description of the common merganser was written by Swedish naturalist Carl Linnaeus in 1758 in the 10th edition of his Systema Naturae. He introduced the current binomial name Mergus merganser. The genus name is a Latin word used by Pliny and other Roman authors to refer to an unspecified waterbird, and merganser is derived from mergus and anser, Latin for "goose". In 1843 John James Audubon used the name "Buff-breasted Merganser" in addition to "goosander" in his book The Birds of America.
The three subspecies differ in only minor detail:
It is 58–72 cm (23–28+1⁄2 in) long with a 78–97 cm (30+1⁄2–38 in) wingspan and a weight of 0.9–2.1 kg (2 lb 0 oz – 4 lb 10 oz); males are on average slightly larger than females, but with some overlap. Like other species in the genus Mergus, it has a crest of longer head feathers, but these usually lie smoothly rounded behind the head and do not normally form an erect crest. Adult males in breeding plumage are easily distinguished, the body white with a variable salmon-pink tinge, the head black with an iridescent green sheen, the rump and tail grey, and the wings largely white on the inner half, black on the outer half. Females and males in "eclipse" (non-breeding plumage, July to October) are largely grey, with a reddish-brown head, white chin, and white secondary feathers on the wing. Juveniles (both sexes) are similar to adult females but also show a short black-edged white stripe between the eye and bill. The bill and legs are red to brownish-red, brightest on adult males, dullest on juveniles.
As with other mergansers, these piscivorous ducks have serrated edges to their bills to help them grip their prey, so they are often known as "sawbills". In addition to fish, they take a wide range of other aquatic prey, such as molluscs, crustaceans, worms, insect larvae, and amphibians; more rarely, small mammals and birds may be taken. As in other birds with this trait, the salmon-pink colouration shown variably by males is probably dietary-derived from the carotenoid pigments found in some crustaceans and fish. When not diving for food, they are usually observed swimming on the surface of the water or resting on rocks in the middle of rivers or hidden in the vegetation along riverbanks, or (in winter) on the edge of floating ice.
In most places, the common merganser is equally at home in salt and fresh water. In larger streams and rivers, they float down with the current for a few miles and either fly back or, more commonly, fish their way back, diving all the way. In smaller streams, they are present in pairs or smaller groups, and they float down, twisting round and round in the rapids, or fishing vigorously in a deep pool at the foot of a waterfall or rapid. When swimming leisurely, they position themselves in the water much like dabbling ducks, but they also swim deep in the water like cormorants, especially when swimming upstream. They often sit on a rock in the middle of the water, similar to cormorants, often with their wings half-open to the sun. To rise from the water, they flap along the surface for many yards. Once they are airborne, their flight is strong and fast.
They often fish in a group forming a semicircle and driving the fish into shallow water, where they are easy to catch. Their normal vocalisation is a low, harsh croak, but during the breeding season, males and juveniles produce a plaintive, soft whistle. They are generally wary, and one or more birds will remain on sentry duty to warn the flock of approaching danger. If disturbed, they will often disgorge food before moving. Although they move clumsily on land, they resort to running when pushed to do so, assuming a very upright position similar to penguins, and frequently falling and stumbling.
Nesting is usually in a tree cavity, so the species requires mature forest as its breeding habitat; they also readily use large nest boxes where these are available, requiring an entrance hole 15 cm (6 in) in diameter. In treeless areas such as the mountains of Central Asia, they use holes in cliffs and steep, high banks, sometimes a considerable distances from the water. The female lays 6–17 (most often 8–12) white to yellowish eggs, and raises one brood per season. The ducklings are carried by the mother on her back to rivers or lakes immediately after hatching, where they feed on freshwater invertebrates and small fish fry, fledging at 60–70 days of age. The young are sexually mature at two years of age. Common mergansers are known to form crèches, with single females having been observed with over 70 ducklings at one time.
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Common merganser
The common merganser or goosander (Mergus merganser) is a large sea duck of rivers and lakes in forested areas of Europe, Asia, and North America. The common merganser eats mainly fish. It nests in holes in trees. The name "common merganser" is used in North America, while "goosander" is used in Eurasia.
The first formal description of the common merganser was written by Swedish naturalist Carl Linnaeus in 1758 in the 10th edition of his Systema Naturae. He introduced the current binomial name Mergus merganser. The genus name is a Latin word used by Pliny and other Roman authors to refer to an unspecified waterbird, and merganser is derived from mergus and anser, Latin for "goose". In 1843 John James Audubon used the name "Buff-breasted Merganser" in addition to "goosander" in his book The Birds of America.
The three subspecies differ in only minor detail:
It is 58–72 cm (23–28+1⁄2 in) long with a 78–97 cm (30+1⁄2–38 in) wingspan and a weight of 0.9–2.1 kg (2 lb 0 oz – 4 lb 10 oz); males are on average slightly larger than females, but with some overlap. Like other species in the genus Mergus, it has a crest of longer head feathers, but these usually lie smoothly rounded behind the head and do not normally form an erect crest. Adult males in breeding plumage are easily distinguished, the body white with a variable salmon-pink tinge, the head black with an iridescent green sheen, the rump and tail grey, and the wings largely white on the inner half, black on the outer half. Females and males in "eclipse" (non-breeding plumage, July to October) are largely grey, with a reddish-brown head, white chin, and white secondary feathers on the wing. Juveniles (both sexes) are similar to adult females but also show a short black-edged white stripe between the eye and bill. The bill and legs are red to brownish-red, brightest on adult males, dullest on juveniles.
As with other mergansers, these piscivorous ducks have serrated edges to their bills to help them grip their prey, so they are often known as "sawbills". In addition to fish, they take a wide range of other aquatic prey, such as molluscs, crustaceans, worms, insect larvae, and amphibians; more rarely, small mammals and birds may be taken. As in other birds with this trait, the salmon-pink colouration shown variably by males is probably dietary-derived from the carotenoid pigments found in some crustaceans and fish. When not diving for food, they are usually observed swimming on the surface of the water or resting on rocks in the middle of rivers or hidden in the vegetation along riverbanks, or (in winter) on the edge of floating ice.
In most places, the common merganser is equally at home in salt and fresh water. In larger streams and rivers, they float down with the current for a few miles and either fly back or, more commonly, fish their way back, diving all the way. In smaller streams, they are present in pairs or smaller groups, and they float down, twisting round and round in the rapids, or fishing vigorously in a deep pool at the foot of a waterfall or rapid. When swimming leisurely, they position themselves in the water much like dabbling ducks, but they also swim deep in the water like cormorants, especially when swimming upstream. They often sit on a rock in the middle of the water, similar to cormorants, often with their wings half-open to the sun. To rise from the water, they flap along the surface for many yards. Once they are airborne, their flight is strong and fast.
They often fish in a group forming a semicircle and driving the fish into shallow water, where they are easy to catch. Their normal vocalisation is a low, harsh croak, but during the breeding season, males and juveniles produce a plaintive, soft whistle. They are generally wary, and one or more birds will remain on sentry duty to warn the flock of approaching danger. If disturbed, they will often disgorge food before moving. Although they move clumsily on land, they resort to running when pushed to do so, assuming a very upright position similar to penguins, and frequently falling and stumbling.
Nesting is usually in a tree cavity, so the species requires mature forest as its breeding habitat; they also readily use large nest boxes where these are available, requiring an entrance hole 15 cm (6 in) in diameter. In treeless areas such as the mountains of Central Asia, they use holes in cliffs and steep, high banks, sometimes a considerable distances from the water. The female lays 6–17 (most often 8–12) white to yellowish eggs, and raises one brood per season. The ducklings are carried by the mother on her back to rivers or lakes immediately after hatching, where they feed on freshwater invertebrates and small fish fry, fledging at 60–70 days of age. The young are sexually mature at two years of age. Common mergansers are known to form crèches, with single females having been observed with over 70 ducklings at one time.