新托福阅读机经背景知识完整版

　　新托福阅读机经背景知识完整版!同学们注意了，今天小编要给同学们带来重要干货，就是机经知识，相信很多同学对机经并不陌生，但是其具体背景和由来想必并不是很了解，下面小编就给大家普及下。

　　Songbirds include those birds from the order Passeriformes, commonly called passerines. There are approximately 5,400 different species of passerines. The suborder Oscine includes those birds that we tend to think of as your typical songbird, those birds that have complex songs as adults. In the majority of Oscines, the male is the one with the complex singing ability, and there is much diversity among males of different species in the length and complexity of their songs.

　　Song needs to be developed, just like any other characteristic of songbird behavior. Singing the correct song for that species is not an instinctual process. The need to sing is instinctual, however what song to sing has been found to be learned. When and where young songbirds learn their songs has long been studied. Just as songbirds differ in their songs, they also differ in their song learning process, though some basic principles seem to be the same. Many species learn their song only during the first few months, though a few can learn songs their entire lives. Also differing between species is from who the songs are learned, and how much of the songs are accurately imitated.

　　Some species may exactly copy the songs they are exposed to. On the other hand, many will not exactly imitate the song or songs that they have been exposed to. Instead they will take bits and pieces of it and invent their own song, though usually similar in construction to that which the species normally sings.

　　The Basic Features of Song Learning

　　Nine males song sparrows were collected from the wild from four differentbroods when they were around 4 to 6 days old. They were raised by people untilthey were weaned at 33 to 35 days old and then were placed into individualwire-mesh cages. Live tutors were used in this experiment. Four wild-caughtadult male song sparrows were used as the tutors. The tutors were placed intoflight aviaries and the subject's cages were placed adjacent to the aviaries, sothat they could have visual contact with one of the tutors, while still beingable to hear the other three singing. Also, the subjects were rotated so thattheir visual contact with one tutor varied between the tutors. The subjects werethere when they were 33 to 94 days old, with the assumption that their sensitivephase lay some time in this time period.

　　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.

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