Scientists have recently discovered that Andean condors (秀鹫)— some of the world’s largest birds——barely flap their wings at all while flying. Instead, they use rising air currents to remain in the air for hours.

The Andean condor is the world’s largest soaring bird. They can weigh up to 15 kilograms. Their wings, when spread out, measure up to three meters. Their main food source is the meat of large animals which have died. Soaring high in the sky allows condors to easily spot possible meals on the ground.

Scientists worked together to study the flight patterns of these huge birds and how much effort the birds use when flying. To study the birds while they were in the sky, the researchers attached special devices which could record every beat of their wings.

The scientists learned that most of the condors’ flapping— over 75%— came when the birds were taking off. Once in the sky, the birds flew for very long periods of time without flapping at all. In fact, they only flapped their wings for 1% of the time they were in the air. One bird flew for over five hours without flapping, covering nearly 117miles.

Soaring without flapping is important because birds burn energy every time they flap their wings.

The birds’ soaring isn’t magic. They use the fact that hot air rises to keep themselves up. As hot air rises, it often creates “thermals”— currents of warm air moving upward. The condors soar by making use of these thermals. The tricky part is finding thermals and moving between them.

When birds are forced to land and take off again often, it costs them a lot of energy. The researchers learned that to avoid having to land, the condors did most of their non-take-off flapping when they were closer to the ground and looking for a new thermal.

The scientists reported that even though all of the condors they studied were young, they knew well how to take advantage of the air currents.

【小题1】What can we learn about the Andean condor from the text?

A．They live mairly on small animals.

B．Their wingspan is at least three meters.

C．They rely on hot air to remain high in the sky.

D．They are the birds with the strongest flying ability.

【小题2】Why was the equipment tied to the birds?

A．To measure how far they could fly without flapping.

B．To keep track of how often they flapped while flying.

C．To calculate the energy required for their flight.

D．To confirm their flight patterns.

【小题3】Which of the following acts consumes the most energy for a condor?

A．Hunting for food.	B．Flying in the sky.
C．Getting off the ground.	D．Landing on the ground.

【小题4】What can we infer from the text?

A．Condors flap the most when looking for a new thermal.

B．No condor can fly for more than five hours without flapping.

C．Condors don’t need to look for thermals when soaring in the sky.

D．Soaring by using thermals is probably a natural ability of condors.