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At what age do geese and swans reach full size?
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Anseriform
Mallard (Anas platyrhynchos).
Geese and swans do not reach their full size until the end of their second year of life. While some other anseriform species may reach adult size and plumage by six months of age, geese and swans maintain a slower developmental trajectory, often retaining immature feathers even after reaching their full physical size at the two-year mark.1