The Development of Orientation Mechanisms in Birds

候鸟和其他种类动物的定向行为研究在很大程度上依赖于定向笼作为分析动物选择方向的手段。对于鸟类来说，这些通常是圆形的笼子，记录着动物跳跃或拍打的方向。这类研究结果的完整性显然取决于研究人员至少了解并经常控制鸟类受到的刺激的能力。由于其他物种的感知世界往往与我们自己的明显不同，研究人员必须极其小心地确保他们的实验对象对感兴趣的刺激做出反应。候鸟已经被证明使用偏振天窗的图案来定位。这是一种人类几乎不敏感的视觉刺激，脊椎动物感知偏振光的生理机制尚不清楚。此外，在技术上不可能精确模拟晴朗天空的偏振光图案。到目前为止，艾布尔博士的实验表明，偏振的天窗可能在几种候鸟的定向能力的发展和表现中起着中心作用。这些事实使得详细研究鸟类对偏振天光的反应变得极其重要：它们对刺激的哪些具体方面做出反应，以及它们如何将信息用作指南针？知道这些将有助于实验者产生最佳的测试刺激和仪器，并将确保鸟类的方向不是基于测试情况的某些未知方面的人工制品。

Studies of the orientation behavior of migratory birds and other kinds of animals rely heavily on orientation cages as the means of assaying the animal's choice of direction. In the case of birds, these are usually circular cages in which the direction of the animal's hopping or fluttering is recorded. The integrity of the results of such studies obviously depends upon the researcher's ability at least to know, and often to control, the stimuli to which the birds are exposed. Because the perceptual world of other species often differs markedly from our own, researchers must be extremely careful to be certain that their experimental subjects are responding to the stimuli of interest. Migratory birds have been shown to use patterns of polarized skylight for orientation. This is a visual stimulus to which human beings are barely sensitive, and the physiological mechanism by which vertebrates perceive polarized light is unknown. In addition, it is technically impossible to simulate precisely the polarized-light pattern of the clear sky. Dr. Able's experiments to date suggest that polarized skylight may be centrally involved in the development and performance of orientation in several species of migratory birds. These facts make it extremely important to examine in detail the birds' response to polarized skylight: To what specific aspects of the stimulus are they responding, and how do they use the information as a compass? Knowing these things will help experimenters produce an optimal testing stimulus and apparatus, and will ensure that the birds' orientation is not an artifact based on some unknown aspect of the testing situation.