SUGGESTIONS FOR THE STUDENT 97 



Describe condition of a Passerine bird at birth and its subsequent 

 plumages and molts. About how long is it in the nest? How long does it 

 wear the Juvenal plumage? What plumage follows? What feathers are 

 usually retained at the postjuvenal molt? When does the prenuptial molt 

 occur? Is it usually complete? What molt is complete? How does the 

 natal down of prsecocial birds differ from that of altricial birds? How long 

 do some Snipe wear the postjuvenal plumage? What variation in the law 

 of molt is shown by Ptarmigan and most swimming birds? Describe changes 

 in color due to wear or fading. Give illustrations of the acquisition by molt 

 of nuptial plumes. Describe differences in color due to age. When do most 

 birds acquire their mature plumage? Mention several species which do not 

 reach full plumage until at least their second year. Describe the plumage 

 changes of the Scarlet Tanager, American Goldfinch, and Bobolink. When 

 the adults are unlike in color, which is usually the brighter? Which parent 

 does the nestling usually resemble? What may be inferred from the spotted 

 Juvenal plumage of the Bluebird? What is Darwin's theory of sexual se- 

 lection? What is Wallace's theory? Describe what is meant by secondary 

 sexual characters and give cases in illustration. What relations exist be- 

 tween the degree of intensity of a bird's color and the climatic conditions 

 under which it lives? Describe the case of the Song Sparrows. Is it believed 

 that their changes in color are due to the direct influence of environment 

 rather than to the influence of natural selection in establishing protective 

 colors? Why are concealing colors necessary? To what factors other than 

 color may a bird owe its comparative immunity from its foes? Are they 

 required by all species? How may we account for the wide range of color 

 in arboreal birds? What is Thayer's principle of counter-shading? Demon- 

 strate this theory with the aid of decoys. What are 'obliterative' markings? 

 What are 'banner' or 'directive' marks? What theories have been advanced 

 to account for their significance? Mention all the birds you know which 

 reveal white marks in flight. What is albinism? melanism? xanthrochroism? 

 erythrism? Describe an albino which you have seen. Did it act like normally 

 colored birds of its own species? What may be learned from observing 

 albinoes or other birds so marked that they may be recognized? Have you 

 ever known a caged-bird to change in color? 



REFERENCES 



1871. DARWIN, C., The Descent of Man, Chaps. XIII-XVL 1877. 



ALLEN, J. A., The Influence of Physical Conditions on the Genesis of Species, 

 Radical Review, I, pp. 108-140. Reprinted in Smithsonian Rep. 1905, pp. 

 375-402. 1891. WALLACE, A. R., Darwinism, Chaps. VIII-XI, (Macmil- 

 lan). 1890. POULTON, E. B., The Colours of Animals, (Appleton). -1893. 

 NEWTON and GADOW, Colors of Birds, in Dictionary of Birds, (Macmillan). 

 1896. STONE, W., The Molting of Birds, Proc. Acad. Nat. Sci., Phila., pp. 

 108-167. 1900. DWIGHT, J., JR., Sequence of Plumages and Moults of the 

 Passerine Birds of New York, Annals, Acad. Sci., XIII, pp. 73-360. See also 

 Auk, XVII, pp. 34, 143, 368. 1907. BEEBE, C. W., Geographic Variation 

 in Birds with Especial Reference to the Effects of Humidity, Zoologica, I, 

 pp. 1-41. 1908. BEEBE, C. W., Seasonal Changes of Color in Birds, Am. 

 Nat., XLII, pp. 34-38. 1909. THAYER, G. H., Concealing Coloration in 

 the Animal Kingdom, 4to., 260 pp., ills., (Macmillan). 1910. TRACY, 

 H. C., Significance of White Markings in Birds of the Order Passeriformes, 

 Univ. Cal. Pub. in Zool., VI, pp. 285-312. 1910. PYCRAFT, W. P., A His- 

 tory of Birds, (London: Methuen & Co.). 1911. BARBOUR, T., and PHIL- 

 LIPS, J. C., Concealing Coloration Again, Auk, XXVIII, 179-188. 1911. 

 THAYER, A. H., Concealing Coloration, Pop. Sci. Monthly, July, pp. 20-35. 

 1911. ROOSEVELT, THEODORE, Revealing and Concealing Coloration in 

 Birds and Mammals, Bull. Am. Mus. Nat. His., XXX, pp. 119-231. 



