Directions: Read the passage carefully. Then answer the questions or complete the statements in NO MORE THAN 25 WORDS.
As skies fill with millions of migrating birds, European scientists say the seasonal miracle appears to depend on a seeming contradiction: The fatter the bird, the more efficiently it flies. The results of their study contradict a central theory of aerodynamics（空气动力学）, which predicts that the power needed to fly increases with weight.
For birds, apparently, the cost of flying with heavy fuel loads is considerably smaller than previously thought. Researchers found that red knot wading birds double their normal body weight of 100 grams before making their twice-a-year, nonstop commute between the British Isles and the Russian Arctic. Distance: 5,000 kilometres.
Another study in the journal Nature measured the benefits of flying in an aerodynamic V formation, which allows birds to save energy by gliding in the lead bird’s air stream.
Flying in formation, their heart rates were as much as 14.5 per cent lower than flying solo, according to Henri Wimerskirch, a French scientist. The findings help explain how birds complete difficult migrations. Researchers had assumed that thinner, more athletic birds would have the best chance of survival.
The first study suggests that building up fat deposits to be burned as fuel during the migration is worth more than the energy it takes to carry the additional weight. Heavier birds apparently use their muscles more efficiently.
In the study, researchers said their team studied the birds flown at different body masses during 28 simulated flights. They were injected with a small amount of water containing a radioactive element that enabled the team to measure the amount of energy burned.
85. How much will a red knot wading bird probably weigh before making its nonstop migrating flight?
86. The additional weight gained before the flight won’t increase the powered needed to fly; on the contrary, it works as _____________________.
87. How did scientists successfully conduct the first study?
88. We can infer from the studies on fat deposits and V formation flying that both factors _____________________________.
