1. Syevettsoff's Periodical Phenomena, p. 251.
2. Seyfferlitz, quoted by Brehm, iv. 760.
3. The Arctic Voyages of A.E. Nordenskjold, London, 1879, p. 135. See also the powerful description of the St. Kilda islands by Mr. Dixon (quoted by Seebohm), and nearly all books of Arctic travel.
4. Elliot Coues, in Bulletin U.S. Geol. Survey of Territories, iv. No. 7, pp. 556, 579, etc. Among the gulls (Larus argentatus), Polyakoff saw on a marsh in Northern Russia, that the nesting grounds of a very great number of these birds were always patrolled by one male, which warned the colony of the approach of danger. All birds rose in such case and attacked the enemy with great vigour. The females, which had five or six nests together on each knoll of the marsh, kept a certain order in leaving their nests in search of food. The fledglings, which otherwise are extremely unprotected and easily become the prey of the rapacious birds, were never left alone ("Family Habits among the Aquatic Birds," in Proceedings of the Zool. Section of St. Petersburg Soc. of Nat., Dec. 17, 1874).
5. Brehm Father, quoted by A. Brehm, iv. 34 seq. See also White's Natural History of Selborne, Letter XI.
6. Dr. Coues, Birds of Dakota and Montana, in Bulletin U.S. Survey of Territories, iv. No. 7.
7. It has often been intimated that larger birds may occasionally transport some of the smaller birds when they cross together the Mediterranean, but the fact still remains doubtful. On the other side, it is certain that some smaller birds join the bigger ones for migration. The fact has been noticed several times, and it was recently confirmed by L. Buxbaum at Raunheim. He saw several parties of cranes which had larks flying in the midst and on both sides of their migratory columns (Der zoologische Garten, 1886, p. 133).
8. H. Seebohm and Ch. Dixon both mention this habit.
9. The fact is well known to every field-naturalist, and with reference to England several examples may be found in Charles Dixon's Among the Birds in Northern Shires. The chaffinches arrive during winter in vast flocks; and about the same time, i.e. in November, come flocks of bramblings; redwings also frequent the same places "in similar large companies," and so on (pp. 165, 166).
10. S.W. Baker, Wild Beasts, etc., vol. i. p. 316.