When the subjects started singing the next spring, their repertoires wereanalyzed. The average was seven song types per subject. This does correspondwith birds raised exclusively in the wild by their parents. Eight of the ninesubjects learned songs from two or more of the tutors and later imitated thesesongs.
In similar experiments in which some birds are exposed to tutors and someare raised in isolation, those birds that were exposed to tutors almost alwaystend to imitate pieces and even complete songs. Those birds raised in isolationalways sang isolate songs. These isolate songs were similar to each other andconsist of much more structurally simpler songs than males raised with normalsong exposure.
重点词汇：
song sparrows: 北美歌雀
broods：窝
aviary：鸟舍
subject：实验的对象
adjacent to：与…连接的
rotated：旋转的
repertoires：整段乐曲
correspond with：相符合，相一致
exclusively：专门的，排外的
isolation：孤立，隔离