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 [Pg 327] 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.