Male peacocks possess feathers, though the spectacular structure most people associate with them is not the true tail. This iconic, iridescent display is scientifically known as the train, an elaborate collection of highly modified feathers used to attract the female peahen. The Indian peafowl (Pavo cristatus) is the most commonly recognized species, famous for this extraordinary plumage. Understanding this feature requires looking closely at its unique anatomy, its evolutionary purpose, and its annual biological renewal.
The Anatomy of the Train
The dramatic fan of feathers, which can measure over five feet long in a mature male, is composed of highly elongated upper tail coverts, not the tail feathers themselves. These specialized feathers grow from the male’s lower back and overlay the much shorter, supporting tail feathers, called rectrices, located beneath. The rectrices are stiff and short, serving the functional purpose of raising and holding the massive train upright during the courtship display.
The striking, vibrant colors seen in the train are not caused by pigment but by structural coloration within the feather barbules. Microscopic, crystal-like structures within the keratin reflect specific wavelengths of light, creating shimmering blues, greens, and bronzes that change with the viewing angle. Each of the roughly 150 to 200 long coverts features a distinct, eye-like pattern at its tip, known as an ocellus or eyespot. This intricate pattern is formed by concentric rings of color, which become the focal point when the peacock erects and fans his train into a massive, shimmering disc.
Sexual Selection and the Purpose of the Display
The peacock’s train is an example of sexual dimorphism, the difference in appearance between males and females of the same species. Peahens possess simple, mottled brown and gray plumage, lacking the male’s long, colorful coverts entirely. This disparity arises from sexual selection, an evolutionary process where one sex, typically the female, chooses mates based on specific traits.
The elaborate train functions as an advertisement of the male’s quality to potential mates. The size, symmetry, and number of eyespots on the train are considered honest signals of the peacock’s genetic health. Growing and maintaining such a cumbersome, energy-intensive structure suggests the male has successfully survived, indicating superior genes and immune function. During courtship, the peacock will vibrate his erected train in a display known as “train rattling,” which creates a shimmering visual effect and low-frequency sounds that entice the peahen.
Annual Renewal of the Train
The elaborate plumage is renewed annually through a process called molting. Male peacocks naturally shed their entire train every year after the conclusion of the breeding season, typically in late summer or early fall. This timing ensures the male is not expending energy on the heavy plumage outside of the mating period.
The shedding process allows the bird to divert energy toward recovery and the regeneration of new feathers. The full regrowth of the complex train takes approximately five to seven months, ensuring the male has a complete and vibrant display by the following spring mating season. The collectible peacock feathers are often gathered after they have been voluntarily dropped by the bird.