Editing Common merganser (section)

===Breeding===
[[Bird nest|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 {{convert|15|cm|in|frac=2|abbr=on}} in diameter.<ref name=duFeu2005/> 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.<ref name=fbi6/> 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.<ref name=Hoyo/><ref name=Madge/><ref name=Snow/> Common mergansers are known to form [[Crèche (zoology)|crèches]], with single females having been observed with over 70 ducklings at one time. <ref name=Mervosh2018/>