Why don't birds get lost on their long flights from one place to another?
Not long ago, experiments showed that birds rely the sun to guide them during daylight hours. But what about birds 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 had spent its lifetime in a cage and had never flown under a (nature) sky. Yet it showed an inborn ability (use) the stars for guidance. The bird's cage (place) under an artificial star-filled sky. The bird tried to fly in the same direction as that (take) by his outdoor cousins. Any change in the position of the make -believe stars caused change in the direction of his flight.
Scientists think that doves, when (fly) in daylight, use the sun for guidance. But the stars are obviously their main means of (fly). What do they do if the stars are hidden by clouds? Apparently, they find their way by such landmarks as mountain ranges, coastlines, and river courses. But when it's too dark to see these, the doves circle (help), unable to get their position.
