Duck decoying is one of the oldest methods of taking winter wild-fowl. It has been practised for centuries, and perhaps nowhere with greater success than in our own country. Owing to its insular position Britain has always been a great resort of fowl, and in times past it was visited by myriad of swans, geese, and ducks, many of which annually remained to breed. The marsh and fenlands of the south-eastern counties constituted tracts alike favourable for food and nesting, and for the most part the birds were undisturbed. But as the plough invaded their haunts the marsh was converted into corn-land, and from that time the breeding sea-fowl have steadily declined in numbers. The oldest decoys were merely adapted sheets of water, but when these, by virtue of having been drained, were no longer available, artificial ones were constructed in likely situations and planted round with timber to secure their privacy. Many of the decoys were farmed by fowlers, and the more valuable afforded a considerable source of revenue to the owners. Speaking of the dwellers in Croyland, Camden says that: "Their greatest gain is from the fish and wild ducks that they catch, which are so many, that in August they can drive at once into a single net three thousand ducks." He further adds that they call the pools in which the ducks are obtained their corn-fields, though there is no corn grown for miles round. For the privilege of taking fish and fowl three hundred pounds sterling were originally paid to the Abbots of Croyland, and afterwards to the king. Although the "driving of ducks" was allowed, a code of Fen laws decreed that neither nets nor engines should be used against the fowl "commonly called moulted ducks" before midsummer day yearly. In the early days of the decoys enormous quantities of fowl were taken in them. As many as 31,200 duck, teal, and widgeon were captured near Wainfleet in a single season, and 2,646 mallards in two days. In these early times it is said that a flock of wild ducks has been observed passing over the Fens in a continuous stream for eight hours together.