Birdsong is the classic example of how genes (hereditary information) and environment both have a crucial role to play in the behavioral development of animals. Since the pioneering work of W. H. Thorpe on chaffinches (a common European bird), many species have been studied, and it has become clear both that learning plays an important role for all species and also that there are constraints on what they are able to learn.

Thorpe was able to show that learning from others was involved in chaffinch birds through a series of experiments on hand-reared chicks (young birds). As in most other species, only the males sing. Thorpe found that, if he raised young males in total isolation from all others, the song they produced was quite different from that of a normal adult. It was about the right length and in the correct frequency range, it was also split up into a series of notes as it should be. But these notes lacked the detailed structure found in wild birds, nor was the song split up into distinct phrases as it usually is. This suggested that song development requires some social influence. Later experiments in which researchers played recordings of songs to young birds showed just how precise this influence was, many of them would learn the exact pattern of the recording they had heard. A remarkable feature here was in the first few weeks of life, yet they did not sing themselves until about eight months old. They are thus able to store a memory of the sound within their brain and then match their own output to their collection of it when they mature.

Young chaffinches normally learn only chaffinch song, though Thorpe found they could be trained to sing the song of a tree pipit (another type of bird), which is very similar to that of their own species. In general, however, the constraints on learning which birds have ensure that they only learn songs appropriate to the species to which they themselves belong. These constraints may be in their brain’s circuitry, the young bird hatching with a rough idea of the sounds that it should copy. The crude song of a bird reared in isolation gives some clues as to what this rough idea may be: the length, the frequency range and the breaking up into notes are all aspects of chaffinch song shared between normal birds and those reared in isolation. In other cases the constraints are more social, young birds only being prepared to learn from individuals with whom they have social interactions. Thus, in a number of species, it has been found that they will not copy from recordings, but will do so from a live tutor. In some cases this may occur when they are young birds, but in others the main learning period is when they set up their territories and interact with neighbors for the first time, enabling them to match their neighbor’s songs and so counter sing with them. Whatever the nature of the learning rules in a particular species, there is no doubt that they are effective, it is very unusual to hear a wild bird singing a song which is not typical of its own species despite the many different songs which often occur in a small patch of woodland.

However, not all birds show the same learning pattern as do chaffinches. There are some species which produce normal sounds even if deaf, so that they cannot hear their own efforts, much less copy those of others. The cooing of doves and the crowing of cocks are examples here. In other cases, such as parrots and hill mynahs, birds can be trained to copy a huge variety of sounds, though those they learn in the wild are usually more restricted. The amazing capability of mynahs has apparently arisen simply because birds in an area learn a small number of their calls from each other, males from males and females from females, and these calls are highly varied in structure. The ability to master them has led the birds, incidentally, to be capable of saying “hello” and mimicking a wide variety of other sounds.

鸟鸣是一个典型例子，表明了基因（遗传信息）和环境是如何在动物的行为发育中起到了关键作用。自从W. H. 索普开拓性地对苍头燕雀（一种欧洲常见鸟类）展开了研究，人们对许多物种进行了研究，并且已经清楚地认识到，对所有物种来说，对其进行研究都很重要，并且所能研究的内容也有一定的限制。 通过对一系列人工饲养的雏鸟（幼雏）进行实验，索普证明他借鉴了其他人对苍头燕雀的研究。与其他大多数物种一样，只有雄鸟才会鸣叫。索普认为，如果他在养育雄鸟时，将其与所有其他鸟类完全隔离，那么这只雄鸟的鸣叫声则与其他成年鸟的鸣叫声完全不同。这是因为正确的鸣叫长度和频率范围，可以将鸣叫分为一系列应有的音符。但是这些音符缺少了野鸟所具有的详细结构，也没有像往常那样把鸣声分成几个明显的片段。这表明社会影响对鸣声的发育过程非常重要。在后来的实验中，研究人员对雏鸟鸣叫进行了记录，结果表明这种影响力是多么精确，许多研究人员通过研究鸣叫记录，了解鸣叫的确切模式。在雏鸟的刚出生的几个星期里，有一个明显的特征，但他们直到八个月大时才开始鸣叫。因此，他们能够将鸣叫声记在其大脑中，然后在他们长大时，将他们发出的鸣叫声与他们的记忆相匹配。 通常，年幼的苍头燕雀只会学习苍头燕雀的鸣声。但索普发现这些年幼的苍头燕雀可以接受训练，发出林鹨（另一种鸟类）的鸣声，这是一种与苍头燕雀十分相似的物种，但年轻的花鸡通常只学习花鸡的歌曲。然而，一般来说，鸟类在学习上的限制确保他们只能学习适合自己的物种的鸣声。这些限制可能存在于他们脑回路中，年幼的鸟大致了解其应该学习的鸣叫声。一只隔离饲养的鸟发出的天然的鸣声给出了一些线索，包括鸣声长度，鸣声频率范围和已分解的音符，这是平常鸟类与隔离饲养的鸟类所共享的鸣声。在其他情况下，这些制约因素更具社会性，雏鸟只打算向与他们有社交互动的鸟类学习鸣声。因此，研究已发现，许多物种不会复制录音中的鸣声，而是在直接向其他鸟类学习。在某些情况下，这可能只会发生在它们还是幼鸟的时候，但在另一些情况下，这些鸟类的主要学习时期是在它们首次建立自己的领地，并与附近的鸟类进行互动时，使它们的鸣声可以与附近鸟类的鸣声相匹配，并能与它们一起鸣叫。不管为什么这种特定物种要按照规则学习鸣声，但是毫无疑问，这种方法是奏效的。听到野生鸟类发出不属于自己种族特有的鸣叫声，这是很不寻常的，尽管在一片小树林中经常会出现许多不同的鸣声。 然而，并不是所有的鸟类都与苍头燕雀的学习模式相同。有些物种即使听不到声音，也会发出正常的声音，所以他们听不到自己的声音，更不用说复制其他鸟类的鸣声了。典型的例子就是鸽子的咕咕声和公鸡的啼叫。在其他情况下，例如鹦鹉和鹩哥这类的鸟，可以通过训练来模仿各种各样的声音，尽管他们在野外学习到的声音通常会比较有限。由于相同地区的鸟类很少听到彼此之间的相互呼叫，雄性呼叫雄性，磁性呼叫磁性，而且它们呼叫声在结构上有很大差异，因而鹩哥的惊人能力就显现了出来。能够掌握这种技能使得鸟类能够说出“你好”，并且模仿各种各样的其他声音。