1. Tame ducks.—Closely observe ducks, both on land and when they are swimming. Where is the heaviest part of the body? Are the legs attached in front of, directly below, or behind the centre of gravity? Is the position of the legs an advantage or a disadvantage (i) in walking, (ii) in swimming? How does the foot differ from the feet of the birds previously mentioned? Between which toes is the web stretched? How are the toes held when the bird lifts its foot in walking? Does it walk gracefully? How does it swim? Are the legs moved together or alternately in swimming? Notice how the web folds up when the foot is moved forwards, and spreads out for the back-stroke. What does the duck eat? How is the food obtained? Why are a duck’s feathers so little wetted by the water? Watch, and describe exactly, how the bird preens its feathers.
How can you distinguish the male (drake) from the female duck, (i) by appearance, (ii) by the voice? Do the colours of the drake’s plumage differ at different periods of the year? What relation have the changes of plumage to the moulting-season? What differences can you observe in the methods of moulting of ducks and fowls? Is there any time of the year when (i) ducks, (ii) fowls are unable to fly? Why? When and where do ducks lay their eggs? Describe the appearance of the eggs. Are young ducks helpless or precocious ([p. 296]), naked or clothed, at hatching? Can they feed themselves? Can they swim?
Examine a dead duck. Notice the thick covering of down-feathers next the skin. What is its use? Examine and draw a foot, and see how the web folds between the toes. Observe the soft, sensitive skin on the outside of the beak; what do you suppose is its use? Notice the shape of the beak. Open it to see the horny plates fringing its inner edge, and notice how these, with other plates on the thick, fleshy tongue, form a strainer.
The duck.—The birds of the duck order—which includes also the geese and swans—differ in many important respects from all our previous types, and it is interesting to observe how perfectly these differences are adapted to the manner of life. On land, the ungainly waddle, which is entailed by the insertion of the hind limbs so far back on the body ([Fig. 212]), shows that the duck is not in an entirely congenial element; in the water the bird is a model of graceful movement, perfectly balanced, progressing smoothly by alternate strokes of its webbed feet, and altering its course to any desired direction with the utmost ease. The duck feeds largely upon the small animals which abound in the water of ponds, and in the mud of the sides, and the beak is beautifully fitted for the duties it has to perform. It is covered on the outside by a soft and highly sensitive skin, which enables the bird to detect with certainty the presence of its prey in the mud; the inner edge of the beak is provided with horny plates which, with similar plates situated on the edge of the thick, fleshy tongue, form a very efficient strainer, by means of which the useless water and thin mud can be forced out at the sides of the mouth and separated from the worms, etc., which were taken into the mouth at the same time. A thick coat of down-feathers, which lies next the skin and contains a great deal of entangled air, forms a non-conducting layer which prevents the undue escape of the heat of the body, and saves the bird from becoming chilled when in the water. Ducks are, moreover, careful to keep their feathers well oiled, and may often be seen preening themselves—applying the bill alternately to the oil-gland on the tail and to the feathers. The completeness with which water flows off a duck’s back is proverbial.
Fig. 212.—Ducks.
During the greater part of the year the brilliant plumage of the drake forms a striking contrast to the sober brown and grey feathers of the female. Another point of difference is that in the male the four middle tail-feathers are curled upwards. From July to October, however, before the moult takes place, the two sexes are very similar in appearance. Birds of the duck order moult in a somewhat different manner from most other birds, in that all the quill-feathers are shed at once, instead of in pairs. Until the new feathers develop, flight is of course out of the question, and the birds remain as secluded as possible in the meantime.
The eggs are white and greasy-looking; they are laid in a rough, open-topped nest, lined with down, which is placed on the ground. The wild duck covers up the eggs when she leaves the nest. The young are active immediately after hatching. It has been noticed that the eggs of precocious birds are generally larger, in proportion to the size of the parent, than those of birds which are naked and helpless at hatching—the larger store of egg-food allowing a more complete development of the young bird in the shell. Further, the nests of precocious birds are, as a rule, less elaborately constructed.