TOEFL Reading: ETS-TOEFL阅读机经 - OB5CRWR6S348NW36L$

Animals that migrate seasonally seem to have formed cognitive maps. A. Important aspects of animals' use of cognitive maps are not understood since the operation of cognitive timing mechanisms remains a mystery. B. When navigating by the Sun and the stars, animals need to keep track of compass direction as well as adjust to other relative changes in Earth's movement and changes in the position of objects in the sky. C. It has been suggested that under cloudy conditions, certain animals that navigate using the Sun and stars are able to sense Earth's magnetic field. D. During seasonal migrations, animals use environmental signs, the Sun, and stars to navigate to wintering sites and back. E. Some animals migrate during the day while others migrate during the night, depending on their genetic programming. F. Future research is likely to show that magnetic sensing alone does not explain how birds navigate when objects in the sky are not visible.