how do this male peacock’s feathers increase ...

Male peacocks grow those huge, flashy tail feathers (the “train”) each year as a sexual signal: bigger, brighter, more symmetrical feathers make them more attractive to females and can also help them look intimidating to rivals or predators.

How a male peacock’s feathers “increase”

A male’s impressive train doesn’t appear full‑size right away; it grows and improves over several years.

• Young males start with much shorter, plainer tail feathers.
• As they mature, each yearly molt replaces old feathers with longer, more colorful ones.
• In peak adult condition, the train can reach over 140–160 cm and make up about 60% of body length when fully spread.

• Growth quality depends on nutrition, hormones, and overall health, so well‑fed, healthy males grow larger, brighter trains.

Why evolution “allows” such big feathers

Those feathers are costly: they are heavy, take energy to grow, and make the bird more visible to predators.

• Females (peahens) prefer males with:
  • longer trains
  • many, evenly spaced eyespots
  • good symmetry and bright color
    These features signal strong genes and good health.

• Because choosy females mate more with well‑ornamented males, those males leave more offspring, so genes for “big, fancy tails” and for “liking big, fancy tails” both spread over generations.

• This is classic sexual selection: a trait that helps reproduction can evolve even if it slightly harms survival, as long as the net reproductive success is higher.

What happens during display

When a male wants to impress a nearby female:

• He raises and fans his train into a huge semicircle.
• He vibrates the feathers at specific frequencies, creating rustling sounds and subtle vibrations that females can sense; males with longer trains tend to use slightly higher vibration frequencies in these courtship displays.

• The iridescent eyespots flash as light hits them at changing angles, making the whole display look dynamic and almost shimmering.

This multimodal performance (visual pattern, motion, sound, vibration) helps maintain the female’s attention and advertise the male’s motor performance and condition.

Quick FAQ style recap

• Do the feathers grow bigger every year?
  Up to maturity, yes; after that, they regrow to about the same impressive size each season, replacing old shed feathers.

• Why are only males so fancy?
  Sexual selection: females choose mates, so males evolved more extreme ornaments as signals of quality.

• Is it only about beauty?
  Not just beauty: the train is a costly, “honest” signal that weak or unhealthy males can’t fake, so it reliably indicates strong genes and good condition.

Information gathered from public forums or data available on the internet and portrayed here.