Sexual selection has dealt the peacock a harsh task. He has to look good and yet survive long enough to breed, unlike the Irish elk! The ostentation of that magnificent train has become familiar, as they survive, almost wild in places where European aristocracy and others took them to add to their showy menageries. The ability to fly is undoubted, but science had failed to discover how much of a literal drag that train was.
Now we know. A paper was published in the JEB yesterday with the title The elaborate plumage in peacocks is not such a drag.
According to the author, Graham Askew of the University of Leeds, the effort to fly involves such great energy that the small extra drag effect has little to no effect on take-off. 5 Indian peacocks with intact trains were tested by startling each individual and filming the result in 3D. Only 200W per kg was required, with or without the train. The drag of a detached train was estimated as 200% of the bird on its own, but as that power is only 0.1% of the total power the bird produces, it has no effect of the performance of the emergency escape or take-off.
Graham estimates that there are costs for this "ornate train." Flight stability, running and production costs have to be important, overshadowed of course by the supreme reward of breeding with peahens. 3% of a bird's metabolic "budget" is dedicated to the growth of that train. The very rare New Zealand hihi was proved to indicate fitness with its plumage in the form of a good diet in - Hihi style and Diet.
The peacock would also be expected to show peahens how suitable he is for mating with his extravagant display of feathery eyes. As far as predators are concerned, there is the possibility of course that any animal would be distracted by the sheer size of the tail or simply impressed by the quality of such a display!