Читать книгу The Behavior of Animals - Группа авторов - Страница 40

Responses to particular stimuli are also subject to internal (e.g., hormonal) and external (e.g., photoperiod) factors (Figure 2.2; see also Chapters 3–8). In spring, when nesting motivation in birds is high, pieces of branch are attractive for nest building. After hatching, a juicy piece of branch may be chosen as food for the nestlings. The sharpness of stimulus identification, too, may depend on the level of motivation. During the mating season, if in a pond there is no female toad rapidly available to a highly motivated conspecific male, the male may clasp even a piece of bark it encounters—somewhat reminiscent of Goethe’s Mephisto who promises Faust “with this drink in your body, soon you’ll greet a Helena in every girl you meet.”