Both sexes undergo the same changes in plumage, but it should be said that these hawks at all ages vary considerably in size and shape, and still more in their colouring. It is not unusual to see an eyess which has the head and parts of the upper plumage nearly black, while the brown of others at the same age is as light as cocoa, with buff edgings. Some detailed remarks as to the size and shape of peregrines and other hawks will be found in Chapter XVIII., where it will be seen that some are of much more prepossessing appearance than others. Speaking generally, the peregrine may be regarded as the most perfect type of combined strength, speed, and destructive power in birds. The proportions are such as could not be altered with any advantage, and adapt the hawk to a greater variety of flight than any other. This reason, and the fact that it is to be found in almost all parts of the habitable world, have always made it a favourite with falconers; and at the present day it is more highly esteemed in Europe than any other, even including the nobler gers. The female--to which sex alone falconers allow the application of the name of falcon--may be flown with success in this country at herons, gulls of all kinds, ducks of all kinds, crows, rooks, grouse, black-game, partridge, pheasant, woodcock, landrail, Norfolk plover, curlew, and other sea birds of about the same size, magpies, wood-pigeons, and doves. She may also generally, if desired, be taught to fly at hares, and no doubt at rabbits. Occasionally she may take plovers and snipe, jackdaws, kestrels, and smaller birds. In India her list includes wild geese, cranes, bitterns, ibis, and bustard. The male peregrine--always called a tiercel (tassel, or tiercelet), because he is about a third smaller in size than his sister--may be flown at gulls, teal, widgeon, partridges, woodcock, landrail, starling, and the smaller sea birds, magpies, and doves; and when exceptionally strong and courageous, will succeed to a greater or less extent with rooks, crows, jackdaws, grouse, wood-pigeons, and kestrels. In India and Eastern countries the francolin and the florican, and several sorts of duck and plovers, may be added to the list.