The male peafowl, known as a peacock, is a member of the pheasant family (Pavo cristatus). The bird is instantly recognizable due to its extravagant plumage, which serves as a spectacular example of evolutionary aesthetics. This article provides a detailed physical description of the peacock, focusing on the structure of its famous train, the colors of its body, and the biological reason behind its elaborate appearance.
The Elaborate Train and Eyespots
The peacock’s most prominent feature is its train, which is composed of highly elongated upper tail coverts, not the tail feathers themselves. This ornamental structure can reach up to five to six feet (150 cm) in length. When fully grown, the train consists of over 200 individual feathers that are shed annually after the breeding season.
Each train feather is adorned with “ocelli,” or eyespots, which are a complex arrangement of color and structure. These iridescent eyespots feature rings of vibrant blue and bronze that catch the light. The three-dimensional appearance of the ocelli is achieved because the feather barbs forming the spot are tightly interlocked by microhooks, keeping the eyespot stable. This structural lock allows the surrounding loose barbs to shimmer independently, creating visual contrast during movement.
Distinctive Body Features and Iridescence
Separate from the train, the peacock’s body exhibits a striking combination of metallic colors. The neck and breast are covered in densely packed, iridescent plumage, typically a deep cobalt blue. This intense coloration is not due to pigment but rather structural coloration, where the microscopic structure of the feathers reflects light to create the brilliant hues.
The peacock’s head is topped with a distinct, upright crest, sometimes called a corona. This crest consists of thin, wire-like feather shafts tipped with small, fan-shaped barbs. The wings are less brightly colored than the body, featuring mottled patterns of brown and black feathers. The peacock is a large bird, weighing between 8 and 13 pounds (4 to 6 kg), supported by long, thick, grayish-brown legs.
The Purpose of the Visual Display
The peacock’s physical attributes are purely for sexual selection and attracting a mate. During courtship, the male raises its train and fans the feathers into an enormous, semi-circular display that can measure several feet across. This behavior is often accompanied by a rapid vibration or shivering of the feathers, a movement known as “train-rattling.”
The shimmering motion and the accompanying rustling sound maximize the visual and auditory impact on the female, or peahen. The vibrancy, symmetry, and number of eyespots on the train serve as honest signals of the male’s overall health and genetic fitness. Peahens inspect these features closely, choosing males whose displays indicate superior vigor and quality.