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Male peacocks have brilliantly colored tail feathers.
Literal
Male-[appositive-の] peacock [topic-は] tail-of plumage [subject-が] color-abundant be-[formal-である].
Natural history register. 雄 (おす) ('male') paired with 雌 (めす) ('female') is the biological male/female distinction for animals. 色彩豊か uses the noun 色彩 ('colors, colorfulness') with the adjective-like 豊か ('abundant, rich'). The formal copula ~である places this firmly in written/educational register — the kind of sentence you'd find in an encyclopedia entry.