16. Max. Perty, Ueber das Seelenleben der Thiere (Leipzig, 1876), pp. 87, 103.
17. G. H. Gurney, The House-Sparrow (London, 1885), p. 5.
18. Dr. Elliot Coues, Birds of the Kerguelen Island, in Smithsonian Miscellaneous Collections, vol. xiii. No. 2, p. 11.
19. Brehm, iv. 567.
20. As to the house-sparrows, a New Zealand observer, Mr. T.W. Kirk, described as follows the attack of these "impudent" birds upon an "unfortunate" hawk.—"He heard one day a most unusual noise, as though all the small birds of the country had joined in one grand quarrel. Looking up, he saw a large hawk (C. gouldi—a carrion feeder) being buffeted by a flock of sparrows. They kept dashing at him in scores, and from all points at once. The unfortunate hawk was quite powerless. At last, approaching some scrub, the hawk dashed into it and remained there, while the sparrows congregated in groups round the bush, keeping up a constant chattering and noise" (Paper read before the New Zealand Institute; Nature, Oct. 10, 1891).
21. Brehm, iv. 671 seq.
22. R. Lendenfeld, in Der zoologische Garten, 1889.
CHAPTER II
MUTUAL AID AMONG ANIMALS (continued)
Migrations of birds. Breeding associations. Autumn societies. Mammals: small number of unsociable species. Hunting associations of wolves, lions, etc. Societies of rodents; of ruminants; of monkeys. Mutual Aid in the struggle for life. Darwin's arguments to prove the struggle for life within the species. Natural checks to over-multiplication. Supposed extermination of intermediate links. Elimination of competition in Nature.