8. Show how the air lying motionless amongst the plumage may serve the same purpose as that in the packing of a fireless cooker or a "thermos bottle." 9. How would the above condition affect the growth and repair of the feather? What connection has it with moulting? 10. What kind of feathers forms most birds' "baby clothes"? What kind forms the adults' "underclothes"? _Suggested drawings._ a. A typical feather. b. A feather of each kind. c. A bird with wings outspread, showing positions of feathers. d. The minute structure of a feather. Birds and Migration _To illustrate Distribution_ Work in the Laboratory _Materials._ Bird skins or mounted birds, at least one representative of each order and, better still, of each family of the birds which pass through or remain in your neighborhood; specimens in a museum may also be used. Some guide to the identification of birds, as Walter's "Wild Birds in City Parks" or Reed's "Bird Guide." A good diagram of a bird. _Directions._ Your object here is to familiarize yourself with the appearance of birds of different types, and with the terms used in describing them. Study first a diagram of a bird and learn the terms and their applications. An important item in the description of a bird is its length. This is obtained by measuring from the tip of the beak, over the curve of the head, to the end of the tail. This measures a curved line and gives a greater length for a bird than the straight line you would naturally estimate. Train your eye by watching house sparrows (so-called English sparrows) and fixing their length as a unit. They are called six inches long, and in the field other birds may be measured by them. The robin is ten inches long, and may be used to measure the larger birds. In describing the colors of birds, great discussions often arise because pupils do not use terms correctly. Consult Chapman's "Birds of Eastern North America" for a color key or chart, and train yourself to observe colors carefully and name them correctly. You will find more colors among birds than are given there, but the chart will help you a great deal. Study in the laboratory as many birds as you can. Try to get one of each order at least and, among the perching birds, one of each family. The answers to the following questions should be recorded upon the blank outlines of birds, or else in the form of a table. _Questions._ 1. How long is the bird? 2. What is the general color of the upper surface; of the lower? 3. What are the markings or peculiarities of the head, if there are any? 4. Note any peculiarities of the tail, as to shape, length, or color, if there are any. 5. If the wings are not like the back, note their color, and, if there are wing bars, note their number and color. 6. What are the markings on the breast, if there are any? 7. Note any other markings, as rump spot, etc. 8. What sort of beak has the bird? 9. What sort of feet has it?