It was suggested in one of the letters to the _Field_ that whilst this is no doubt the general rule there is at least one exception to it. “If asked,” said the writer, “to quote any instance when the smaller bird is faster than a larger one of similar type, I should say that the pochard (_Fuligula ferina_) is faster on the wing than the common mallard, as I have seen the former pass mallards on the wing when both have been flying before a falcon. But from my experience of over thirty years as a falconer, a naturalist, and a shooter, I should say that the above case is one of the rare exceptions where the heaviest bird is not the fastest on the wing if each bird is trying its hardest and best.” Colonel Meinertzhagen, whilst agreeing that the heavier bird of similar type is the faster flier once it gets going, has kindly sent me the following observations on the foregoing statements as to the pochard and mallard. “The common pochard is not a bird of ‘similar type’ to a mallard, the one being a diving duck and the other surface-feeding. They differ in the proportion of wing area to body weight, also in bone structure. The pochard and all diving duck, probably fly faster than surface-feeding duck under similar conditions, having heavier bodies in proportion to the wing area than is ever found among surface-feeding duck. The eider duck, which is even heavier than the ordinary diving duck (_Nyroca_), probably flies faster than them all when once started.” 4. _There must be a standard length of flight to which the test is to be applied._ If the question were asked, “Who is the faster runner, A or B?” the reply would surely be “To what distance are you referring?” A short or a long distance? Applying the analogy, it is obvious that a bird might be much faster than another for a short distance, but if the flight has to be prolonged, may not have the lasting powers of another bird, and therefore would be beaten on the longer course.