Volume 1

The geographical distribution of animals : with a study of the relations of living and extinct faunas as elucidating the past changes of the earth's surface / by Alfred Russel Wallace.

Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: The geographical distribution of animals : with a study of the relations of living and extinct faunas as elucidating the past changes of the earth's surface / by Alfred Russel Wallace. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    50/578
    [part I. best suited to a bird's habits, are probably the causes wliich mark out the exact limits of the range of each species; to which must be added the prevalence of enemies of either the parent birds, the eggs, or the young. In the Malay Arcliipelago pigeons abound most where monkeys do not occur; and in South America the same birds are comparatively scarce in the forest plains where monkeys are very abundant, while they are plentiful on the open plains and campos, and on the mountain plateaux, where these nest-hunting quadrupeds are rarely found. Some birds are confined to swamps, others to mountains; some can only live on rocky streams, others on deserts or grassy plains. The Phenomena of Migration.—The term migration is often applied to the periodical or irregular movements of all animals; but it may be questioned whether there are any regular mi- grants but birds and fishes. The annual or periodical movements of mammalia are of a different class. Monkeys ascend the Himalayas in summer to a height of 10,000 to 12,000 feet, and descend again in winter, Wolves everywhere descend from the mountains to the lowlands in severe weather. In dry seasons great herds of antelopes move southwards towards the Cape of Good Hope. The well-known lemmings, in severe winters, at long intervals, move down from the mountains of Scandinavia in immense numbers, crossing lakes and rivers, eating their way through haystacks, and surmounting every obstacle till they reach the sea, whence very few return. The alpine hare, the arctic fox, and many other animals, exhibit similar phenomena on a smaller scale; and generally it may be said, that whenever a favourable succession of seasons has led to a great multipli- cation of any species, it must on the pressure of hunger seek food in fresh localities. For such movements as these we have no special term. The summer and winter movements best corres]Dond to true migration, but they are always on a small scale, and of limited extent; the other movements are rather temporary incursions than true migrations. The annual movements of many fishes are more strictly analogous to the migration of birds, since they take place in large bodies and often to considerable distances, and are