A displaying peacock raises what looks like a vast tail. Anatomically it is not one. The eyed feathers are upper tail coverts, growing from the rump ahead of the tail proper and reaching well over a metre in a mature bird. The genuine rectrices, about twenty of them, are much shorter and plain, and they brace the coverts from behind when the fan is erected.
The train is grown afresh each year and moulted after the breeding season, so a peacock spends part of the year without it. Each ocellus, the eye-spot, gets its blue and green from photonic crystal structure in the barbules rather than from pigment, which is why the colours shift with viewing angle.
One popular claim deserves care. Females do attend to train condition, but studies disagree on how strongly eye-spot number predicts mating success, and some find little relationship at all.