Mutual Aid: A Factor of Evolution. kniaz Petr Alekseevich Kropotkin

H.W. Bates, The Naturalist on the River Amazons, ii. 59 seq.

      11. N. Syevertsoff, Periodical Phenomena in the Life of Mammalia, Birds, and Reptiles of Voroneje, Moscow, 1855 (in Russian).

      12. A. Brehm, Life of Animals, iii. 477; all quotations after the French edition.

      13. Bates, p. 151.

      14. Catalogue raisonne des oiseaux de la faune pontique, in Demidoff's Voyage; abstracts in Brehm, iii. 360. During their migrations birds of prey often associate. One flock, which H. Seebohm saw crossing the Pyrenees, represented a curious assemblage of "eight kites, one crane, and a peregrine falcon" (The Birds of Siberia, 1901, p. 417).

      15. Birds in the Northern Shires, p. 207.

      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).