When you have collected a number of eggs, place them under hens, having first satisfied yourself that the hens are good sitters. Eight to ten sittings of twelve eggs each is a good number to put down as a start, as from this number you ought to get about a hundred ducklings, and these, when old enough, can be divided into two runs of about fifty each. I have found by experience that it is unwise to put a larger number than this together until the birds are about six or seven weeks old. Naturally, the number of eggs you can put down will depend on the size of your stock and the number of sitting hens at your disposal.
A certain amount of care is necessary in preparing the nest for the hens, as ducks' eggs are very fragile, and much more easily broken than hens' eggs.
The following is the method which I recommend. Get any square box of sufficient depth, and having cut some pieces of sod, build up the corners of the box with them: then cut a square sod to fit the size of the box, and having removed some of the earth underneath the centre of the sod, place it grass upwards in the box. By this means you will obtain the proper shape for the nest, viz., a gradual slope down from the sides to the centre; this will prevent your hens accidentally kicking eggs from under them, as owing to the shape of the nest any eggs which are displaced must roll towards the centre or lowest part of the nest; there is consequently little danger of any of the eggs getting cold. After this, line the nest with dry moss. The sod underneath has the advantage of producing greater heat, and gives a more satisfactory hatch out than nests made of other material, and being firm does not lose its shape.
Don't forget to give your sitting hen some ventilation, but be careful that no draught can reach the eggs.
The sitting hens will, of course, be taken off to feed regularly every day, and you will find them give you less trouble if you take care to tether them on the same leg each day.
And now to return to the laying ducks.
As time goes on you must leave more eggs in the nest, as the birds will soon want to sit. A duck shows signs of this by lining her nest with down from her breast, and in a short time you will find the whole nest, sides and bottom, lined with a thick covering of down; while the eggs are covered by what I can best describe as a thick movable quilt, which protects them from the cold, and the prying eyes of carrion crows and other poachers.
At this time you will observe the old duck staying longer and longer on her nest each day as she lays the last egg or two, and you may be sure that she has fairly begun to sit if you find her still on her nest about 6 or 7 P.M. A day or two before she begins to sit, her nest should be made up to its proper complement of eggs, and it is always wise to keep a few eggs in hand for such contingencies. The number of eggs a duck can sit on depends largely on the size of the duck and also the depth and breadth of the nest; given favourable conditions a duck can manage sixteen or seventeen eggs, and I knew of one nest, consisting of sixteen eggs, all of which hatched off. There is, however, this risk, that should bad weather come it is practically impossible for a duck to successfully brood so large a number as sixteen ducklings, even when her coop is turned away from the wind and rain; and it is here that large brooding hens such as the Bufforpington score their strongest point as mothers to young ducks.
Of one thing you may be sure, a duck will not retain any more eggs in her nest than she can conveniently cover. I know of one case where a duck belonging to me was sitting on fifteen eggs. All appeared to be going well, until one morning a friend of mine, on whose veracity I can absolutely rely, saw the duck fly from her nest, close to where he was standing, with an egg in her bill.