Why do peacocks have colorful tails?

Answer: Sexual selection by peahens

Sexual selection by peahens ✓ — Correct! Elaborate mating display! Male peacock (peafowl) tail isn't true tail—elongated upper tail coverts (200+ feathers). Sexual selection: peahens choose mates based on tail quality. Indicators: (1) Feather quantity—more 'eyes' (ocelli) = healthier male. (2) Vibrant colors—structural coloration from photonic crystals. (3) Display vigor—shaking creates rustling sound. Handicap principle: maintaining huge tail is costly—proves genetic fitness. Only males have elaborate tails. Tail folded when not displaying!

Warning predators of poison — Wrong. Peacocks aren't poisonous. Colorful tail is sexual selection—displaying genetic fitness to attract mates.

Temperature regulation system — Wrong. Large tail doesn't regulate temperature—it's sexual ornament. Display is for attracting peahens based on tail quality.