The difference between male and females in a species has never been more clear than in peacocks. The females, having no need to show off, are much duller than the very vibrant males.
It is common sense that the plumage increases the male peacock’s attractiveness, but it seems almost ambivalent. The massive feathers might be a desirable characteristic but a male peacock without the feathers would be able to escape a fox with greater ease. Extra extravagant features on any animal, whether they be birds, mammals or lizards, will only serve to increase the creatures weight. Although it seems like common sense that the extra weight would contribute to more energy being used to locomote it turns out this may not be true. A simple piece of science where the energy expenditure per metre moved was calculated for male peacocks in the mating season when they had a full train of feathers and compared to their expenditure a few months later when the feathers had been shed. it was found that the peacocks used less energy when they carried their full tail then when they lacked it (this doesn’t necessarily mean that having the tale has no disadvantage as there must be energy lost growing it). It is still quite unclear why and the peacock can gain this counter intuitive efficiency but it is very probable that the assumption that the gained weight will slow the bird down fails to consider seasonal muscular, skeletal and metabolic changes.