Any of various large aquatic birds of the familyAnatidae chiefly of the genera Cygnus and Olor, having webbed feet, a long slender neck, and usually white plumage.
天鹅：鸭科的各种大型水禽，主要是天鹅和哑天鹅属，有蹼足、长而细的脖子和通常为白色的羽毛。
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"If it looks like a duck, and quacks like a duck, we have at least to consider the possibility that we have a small aquatic bird of the familyAnatidae on our hands," said Rose, quoting Douglas Adams.