Читать книгу Migration of Birds (1979) - Frederick Charles Lincoln - Страница 13

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Orientation and Navigation

Studies on how migrating birds orient (travel in one compass direction) or navigate (travel toward a specific goal) have received increasing emphasis in the past 20 years. These studies have focused on the ability of birds to orient themselves by the position of the sun and stars. Outstanding in this facet of research have been the works of Matthews (1951, 1955), Kramer (1952, 1959, and 1961), Sauer and Sauer (1960), Mewaldt and Rose (1960), Sauer (1961), Hamilton (1962a, b), Schmidt-Koenig (1963, 1964), and Emlen (1969). The basic method used in the experiments is to observe the direction in which confined birds attempt to move during the period of migratory restlessness. The birds are not permitted to have any view of the landscape but only the sky above them. In some cases the positions of the celestial bodies are changed by the use of mirrors to see the effect on the orientation of the experimental birds. In other cases the experiments are performed in planetariums so positions of the stars in the artificial heavens can be manipulated and the effect observed.

Physiology of Migration

The physiological basis for bird migration has received considerable attention, particularly the effects of seasonal increases and decreases in daylight and the seasonal rhythms occurring within animals and referred to as "biological clocks." Investigations in this field include the pioneering work on the relationship of photoperiod (daylength) to migration by Rowan (1925, 1926) and many subsequent studies (Wolfson 1940, 1945; Marshall 1961; King, Barker and Farner 1963; King and Earner 1963; King 1963; Farner 1955, 1960; and Farner and Mewaldt 1953). These studies have become ever more deeply involved in the intricate relationships between photoperiod, endocrine interactions, gonad development, fat deposition, and migratory unrest. They add to our knowledge of the mechanisms that regulate the migratory behavior we observe.