Why don’t birds get lost on their long flights from one place to another Scientists have puzzled over this question for many years. Now they’re beginning to fill in the blanks.
Not long ago, experiments showed that birds rely on the sun to guide them during daylight hours. But what about birds that fly by night Tests with artificial stars have proved that certain night - flying birds are able to follow the stars in their long- distance flights.
A dove (鸽子)had spent its lifetime in a cage and had never flown under a natural sky. Yet it showed an inborn ability to use the stars for guidance. The bird’s cage was placed under an artificial star-filled sky. The bird tried to fly in the same direction as that taken by his outdoor cousins. Any change in the position of the artificial stars caused a change in the direction of his flight. But the stars are apparently their principal means of navigation(航行)only. When the stars are hidden by c
A. other relatives
B. the other doves of the same brood (n.窝)
C. doves under the natural sky
D. other birds in general
Why don’t birds get lost on their long flights from one place to another Scientists have puzzled over this question for many years. Now they’re beginning to fill in the blanks.
Not long ago, experiments showed that birds rely on the sun to guide them during daylight hours. But what about birds that fly by night Tests with artificial stars have proved that certain night - flying birds are able to follow the stars in their long- distance flights.
A dove (鸽子)had spent its lifetime in a cage and had never flown under a natural sky. Yet it showed an inborn ability to use the stars for guidance. The bird’s cage was placed under an artificial star-filled sky. The bird tried to fly in the same direction as that taken by his outdoor cousins. Any change in the position of the artificial stars caused a change in the direction of his flight.
But the stars are apparently their principal means of navigation(航行)only. When the stars are hid
A. have been known to scientists for many years
B. have only recently been discovered
C. are known by us
D. will probably remain a mystery
Why don't birds (1) lost on their long flights from one place to another Scientists have puzzled over this (2) for many years. Now they are beginning to fill (3) the blanks.
Not long ago, experiments (4) that birds rely on the sun to guide them (5) daylight, hours. But what about birds (6) fly by night Tests with artificial stars have proved that (7) night - flying birds are able to follow the stars in their long - distance (8) A dove had spent its lifetime in a cage and had never flown under a (9) sky. Yet it showed a(n) (10) ability to use the stars for guidance. The bird's cage was placed under a (n) (11) star - filled sky. The bird tried to fly in the position as that (12) by his outdoor cousins. Any (13) in the position of the make believe stars caused a change (14) the direction of his flight.
(15) think that doves,
A. wonderful
B. great
C. incomparable
D. inborn
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