Would you raise the bird that murdered your children? - Steve Rothstein

翻译人员: KIWI KIWI 校对人员: Yuwei Wu

This is a little bee-eater’s nest.

这是一个食蜂鸟巢。

But this is not a little bee-eater chick.

但这并不是一只小食蜂鸟。

It’s a newly hatched honeyguide— and it’s much more lethal.

这是一只刚孵出的蜜鴷， 它的致命性要高得多。

When its mother placed it here, she punctured all the other eggs in the nest.

母亲把它放在这里时， 刺穿了巢里所有的蛋。

However, one little bee-eater chick survived the attack and is now hatching.

然而，一只小食蜂鸟在这次袭击中 幸存下来，现在正在孵化。

Although the honeyguide nestling is still completely blind,

虽然蜜鴷仍然完全看不见，

it instinctively stabs the little bee-eater chick

它还是本能地用它锋利的钩状喙 刺死了小食蜂鸟。

with its sharp, hooked beak.

And over the following weeks,

在接下来的几周里，

the host parents devotedly care for the hatchling

宿主父母全心全意地照顾着 将它们的孩子杀死的小蜜鴷。

that murdered their offspring.

This is but one example of brood parasitism,

这只是巢寄生的其中一个例子，

an evolutionary strategy in which one animal tricks another

它是一种动物欺骗另一种动物 为自己养育后代的进化策略，

into rearing its young.

It’s especially well-known among birds.

在鸟类中尤其常见。

By depositing their eggs into a stranger’s nest,

通过把蛋放在宿主的巢里，

brood parasites are able to shift the major costs of parenting onto others.

寄主能够将养育子女的主要成本 转移到宿主身上。

Brood parasite chicks usually hatch early,

寄生的幼雏通常很早孵化,

then monopolize their host parents’ attention.

之后就独占宿主的照料。

Some stab their fellow nestlings to death,

有些会刺死其它的雏鸟，

while others shove the remaining occupants out of the nest.

有些则会将剩下的居住者挤出巢。

Meanwhile, others are less harmful to their hosts.

与此同时，其它寄主 对宿主的危害较小。

Not all brood parasites kill all of their host’s offspring outright.

并不是所有的寄主 都会杀死宿主的所有后代。

Brown-headed Cowbirds usually outcompete them

褐头牛鹂选择用自己的大嘴竞争，

by begging for food louder, more frequently, and with a wider mouth.

通过更大声、 频繁地乞讨食物来战胜对手。

Among the most benign,

其中最温和的，莫过于

black-headed ducks lay their eggs in other nests to be incubated.

黑头鸭把蛋产在其它巢里孵化，

However, a few hours after hatching, they simply saunter off.

然而，孵化几个小时后， 它们只是溜达着离开。

But in the most egregious cases of brood parasitism,

但是在巢寄生最恶劣的情况下,

why don’t host parents take a stand?

为什么宿主不表态？

In fact, hosts will often drive adult brood parasites away from their nests,

事实上，它们通常会将 成年的寄主驱赶出巢，

and many take their defenses further.

许多宿主还会 采取进一步的防御措施。

But whether a hosts can recognize and reject parasitic eggs and nestlings

但是它们能否识别 并拒收寄主的蛋和雏鸟

seems to depend on a few factors.

似乎取决于几个因素。

Eastern phoebes will accept

东菲比霸鹟会收容 褐头牛鹂的斑点蛋，

a Brown-headed Cowbird’s speckled egg into their nest,

though theirs are pure white.

虽然它们自己的蛋是纯白色的。

The gray catbird, on the other hand,

另一方面，灰猫嘲鸫

is an expert at rooting out the very same parasites.

是铲除同一类寄主的专家。

It memorizes what the first egg in its nest looks like,

它会记住巢中第一个蛋的样子,

which is usually its own, and tosses any aberrations.

通常是它自己的蛋， 并抛出任何异常的蛋。

This retaliatory adaptation can fuel an evolutionary arms race

这种报复性的适应 助长了进化的“军备竞赛”，

where brood parasites evolve eggs that closely mimic their host’s.

寄主进化出了与宿主非常相似的蛋。

Interestingly, birds that do reject parasitic eggs

有趣的是，那些会排斥寄主的鸟类

are usually clueless when it comes to parasitic chicks.

通常对寄生的雏鸟一无所知。

Reed warblers are good at ejecting poorly matching cuckoo eggs.

芦苇莺擅长逐出品相异常的杜鹃蛋。

But if one hatches in their nest,

但如果有一只杜鹃在巢中孵化，

they’ll care for it even after it’s grown six times their size.

即使它长到了自己的六倍大， 芦苇莺还是会照顾它。

Though chick rejection is a rarer phenomenon,

虽然拒收雏鸟是很罕见的现象，

there are some noteworthy examples.

还是有一些值得我们注意的例子。

While incubating its eggs, the Australian superb fairy-wren sings to them,

在孵蛋的时候，澳大利亚的 壮丽细尾鹩莺会为雏鸟唱歌,

imparting a unique note that its chicks use as a kind of password.

赋予它们一种独特的音符密码。

When a cuckoo is in the wren’s nest, it hatches first and pushes the others out.

杜鹃在鹩莺的巢中时，会先孵化， 然后将其它的鹩莺挤出去。

But, perhaps because it hatched sooner,

但也许是因为它孵化得更快，

the cuckoo chick wasn't able to learn the password,

杜鹃雏鸟没有学会密码,

and so it doesn’t croon the right begging call.

因此它不会哼唱正确的音符。

At this point, the adults usually abandon their nest and start another.

在这种时候，成鸟通常会离开鸟巢， 并建立一个新巢。

Altogether, host species show a remarkable variety of responses.

总之，宿主们表现出了 非常多样化的反应。

This seems to partially be a result of how long

这在一定程度上似乎是取决于 巢寄生进入它们生活环境的时间，

brood parasitism has been in their environment,

and thus how much time they've had to evolve suitable adaptations.

即意味着它们有多少时间进化出 适应的能力。

In fact, studies have shown that those hosts that reject parasitic eggs

事实上，研究已经表明， 那些能够拒收寄主的蛋的宿主，

less frequently can visually distinguish between their eggs and a brood parasite’s.

很少能从视觉上区分两者。

They simply lack a response to the visual information.

它们只是对视觉信息缺乏反应。

This is probably because, before brood parasitism appeared,

这可能是因为在巢寄生出现之前,

responding would have likely had no adaptive value.

反应没有适应性价值。

And even when hosts do recognise a parasite,

即使宿主能够识别寄生者，

getting rid of it may not be the best option.

处理掉也可能不是最好的选择。

The host, especially if it’s small, might not be able to kill the parasite—

宿主，特别是小型宿主， 可能无法杀死寄生者—

or could risk breaking its own eggs in the process.

或者在这个过程中 有打破自己的蛋的风险。

Unless the brood parasite kills all of the host’s young,

除非所有雏鸟都被寄生者杀死，

it may be best to simply foster the imposter.

最好的方法还是抚养这个冒牌货。

Brood parasitism tends to evoke horror and disdain.

巢寄生往往会引起 人们的恐惧和鄙夷。

But why should it be thought of as any more objectionable

但是，为什么它就应该 比捕食者与猎物的关系更令人反感呢？

than predator-prey relationships?

And is it ever productive to impose human morals onto other animals?

把人类的道德观强加于 其它动物身上，有什么好处吗？

Or does it end up saying more about us than it does them?

还是它最终描述的 其实更多是我们自己？

Whichever way you swing it,

不管你怎么想，

brood parasitism is yet another example of the fascinating turns evolution has taken.

巢寄生都是一例令人着迷的 进化的转折。