But that's just one of the thousand or more that it knows,

但這只是牠會唱的千種歌聲中的其中一種

and it's not the only avian virtuoso.

而牠也並非唯一的鳥類歌唱家

A wood thrush can sing two pitches at once.

黃褐棕鶇一次能唱出兩種不同音高

A mockingbird can match the sounds around it, including car alarms.

小嘲鶇能模仿牠周遭的聲音，包括汽車警報聲

And the Australian superb lyrebird

而澳洲華麗琴鳥

has an incredible, elaborate song and dance ritual.

則擁有難以置信的精緻歌聲和舞蹈儀式

These are just a few of the 4,000 species of songbirds.

上述只是 4000 種鳴禽中的其中幾種

Most birds produce short, simple calls,

大部分的鳥類能發出簡單的短鳴聲

but songbirds also have a repertoire of complex vocal patterns

但鳴禽除此之外還具有發出複雜聲音的能力

that help them attract mates,

這能幫助他們吸引伴侶

defend territory,

保護地盤

and strengthen their social bonds.

以及加強他們的社交連結

Each songbird species has its own distinct song patterns,

每種鳴禽都有他們獨特的歌唱模式

some with characteristic regional dialects.

有些歌唱模式帶有地域性方言的特色

Experienced listeners can even distinguish individual birds by their unique songs.

經驗豐富的聽者甚至能依照牠們獨特的歌聲，辨認出牠們是哪一種鳥類

So how do birds learn these songs in the first place?

那麼鳥類一開始是如何學習這些歌聲的呢？

How do they know to mimic the songs of their own species?

牠們怎麼知道要模仿牠們種族的歌聲？

Are they born knowing how to sing?

難道牠們天生就會唱歌嗎？

A lot of what scientists know about bird song comes from studying zebra finches.

許多科學家所知關於鳥類歌唱的知識，都是來自對斑胸草雀的研究

A baby male zebra finch typically learns to sing from its father or other males,

雄性斑胸草雀寶寶通常從爸爸或其他公鳥身上學習唱歌

starting while it's still a fledgling in the nest.

牠從還是巢中雛鳥的年紀，就開始學習這項技能了

First comes a sensory learning phase,

一開始是感官學習階段

when the baby finch hears the songs sung around it and commits them to memory.

斑胸草雀寶寶會聽周遭的歌聲，並把這些聲音記起來

The bird starts to vocalize during the motor learning phase,

在動作學習階段，斑胸草雀寶寶會試著發聲

practicing until it can match the song it memorized.

並不斷練習，直到牠的發聲和記憶中的聲音相符

As the bird learns, hearing the tutor's song over and over again

對鳥兒的學習而言，不斷的聆聽指導者的歌聲是有用的—

is helpful— up to a point.

但有個限度

If he hears it too many times, the imitation degrades—

如果牠聽太多次，模仿能力反而會降低—

and the source matters.

學習對象的樣子也會影響模仿能力

If the song is played through a loudspeaker,

如果歌聲是從揚聲器裡傳出

he can't pick it up as easily.

牠就無法輕易地學習

But hide the same loudspeaker inside a toy painted to look like a zebra finch,

但如果把揚聲器藏在一個斑胸草雀造型的玩具裡

and his learning improves.

牠的學習能力就會上升

What if the baby never hears another zebra finch's song?

如果斑胸草雀寶寶從來沒聽過任何斑胸草雀的歌聲會怎麼樣？

Interestingly enough, it'll sing anyway.

有趣的是，牠無論如何還是會唱歌

Isolated finches still produce what are called innate or isolate songs.

與群體孤立的斑胸草雀仍會唱歌，我們稱此為本能歌聲或孤立歌聲

A specific tune might be taught,

特殊的歌唱旋律是被教導的

but the instinct to sing seems to be hardwired into a songbird's brain.

但本能歌聲似乎與生俱來就在鳴禽的大腦裡

Innate songs sound different from the “cultured” songs

在一開始，本能歌聲聽起來和從其他鳴禽那裡

learned from other finches—at first.

學來的「社會化」歌聲不同

If isolated zebra finches start a new colony,

但若與群體孤立的斑胸草雀發展出一個新群體

the young birds pick up the isolate song from their parents.

幼鳥將會從父母那學習本能歌聲

But the song changes from generation to generation.

但這個歌聲在每一代都會改變

And after a few iterations,

在數次的迭代後

the melody actually starts to resemble

牠們唱出來的旋律就會像

the cultured songs sung by zebra finches in the wild.

野生斑胸草雀所唱的社會化歌聲一樣

Something about the learning process must be hardwired, too,

看來，在斑胸草雀學習歌聲的過程中，有些機制是與生俱來的

drawing the birds towards the same song patterns again and again.

它會不斷的讓鳥兒漸漸朝著相同的歌唱樣式發展

This means that basic information about the zebra finch song

這說明了斑胸草雀歌聲的基本訊息

must be stored somewhere in its genome,

可能被儲存在他們基因組內的某處

imprinted there by millions of years of evolution.

在數百萬年的演化中銘刻於基因

At first, this might seem odd,

這一開始聽來可能有點奇怪

as we usually think of genetic code as a source of biochemical or physical traits,

畢竟我們通常認為，基因密碼應該是生化或身體特徵的源頭

not something like a behavior or action.

而和習性，行為等特性無關

But the two aren't fundamentally different;

但其實這兩者在本質上並無不同

we can connect genomes to behavior through brain circuitry.

我們能從大腦迴路來連結基因組和習性的關聯

The connection is noisy and quite complex.

這個連結十分複雜，也有許多嘈雜的訊號在上面流動

It doesn't simply map single genes to single behaviors, but it exists.

而且它不是以「一個基因對應到一個行為」這樣的方式做連結，但這個連結確實存在

Genomes contain codes for proteins that guide brain development,

基因組中含有能支配大腦發展的蛋白質密碼

such as molecules that guide the pathways of developing axons,

像是引導軸突路徑的發展分子

shaping distinct circuits.

能塑造獨特的腦迴路

Birds' brains have so-called “song circuits”

鳥兒的大腦有所謂的「歌唱迴路」

that are active when the birds sing.

在牠們唱歌時，這個迴路會活躍起來

These circuits also respond to the song of a bird's own species

比起其他種族鳥類的歌聲，這類迴路對鳥兒本身種族的歌聲

more strongly than to other species' songs.

有更強烈的反應

So the theory is that a bird's genes guide development of brain circuits

因此這個理論說明了：鳥類的基因會引導他們腦中

that relate to singing and the ability to learn songs.

有關唱歌和學習歌聲的迴路發展

Then, exposure to songs shapes those neural circuits

再來，暴露在歌聲中能形塑牠們的神經迴路

to produce the songs that are typical to that species.

並產生牠們種族典型的歌聲

Genetically encoded or innate behaviors aren't unique to songbirds.

基因編碼或先天行為並不特別發生在鳴禽身上

They're widespread in the animal kingdom.

這些機制也廣泛的散佈在動物世界中

Spectacular examples include

比較引人注目的例子有

the long-distance migrations of monarch butterflies and salmon.

會長距離遷徙的帝王斑蝶和鮭魚

So what does this mean for humans?

那麼這些現象對人類的意義是什麼呢？

Are we also born with innate information written into our genomes

我們是否也具有天生銘刻在我們基因組內的訊息

that helps shape our neural circuits,

能幫助形塑我們的神經迴路

and ultimately results in something we know?

並在最後導致我們已知的事物呢？

Could there be some knowledge

是否可能有那樣一些知識

that is unique and intrinsic to humans as a species?

對人類這個種族來說是獨特和天生的呢？