奇速英语

澳洲王吸蜜鸟，歌声是这样找回的（完形填空）

Less than a century ago, huge flocks of regent honeyeaters flew all over southeastern Australia. Today, they’re one of the country’s most ____1____ birds. As their numbers decreased, so did the complexity of males’ songs — with potential ____2____ to their breeding success. Now, researchers have restored the regent honeyeater’s traditional song by bringing in tutors: two wild-born male birds who ____3____ their knowledge to captive-born birds.

Fewer than 250 regent honeyeaters are ____4____ to remain in the wild, and past research has shown that many young males — unable to learn their own song from older birds — have been singing the sounds of other species or otherwise ____5____ tunes. That’s why a team of scientists worked to ____6____ the regent honeyeater’s traditional song to birds bred at two zoos in Australia.

At the start, the researchers played recorded songs to young birds — a method that ultimately ____7____, says study co-author Daniel Appleby. ____8____, Appleby and his colleagues gave other young birds real teachers. Two wild-born males who knew the correct regent honeyeater tune ____9____ their days alongside captive chicks. This time, the plan worked.

The researchers soon learned that the teacher-to-pupil proportion ____10____. “We realized that if you have too many birds to one tutor — so a big class size — they don’t learn as ____11____,” Appleby says. They began to keep groups to no more than five students per teacher, and then those who learned the song well sounded extremely ____12____ to the wild birds.

Within three years, the ____13____ of young birds that learned the traditional song went from 0 to 42 percent. Today, more than half of the zoo-bred males sing songs ____14____ to the traditional one. The researchers hope that as they ____15____ more of these animals into the wild, the population will grow and the melody will spread.