原文视听

As their mother returns,
它们的母亲回来了
she sees what the larger chick has done.
她看到了大雏鸟的所作所为
The smaller chick seeks its mother's comfort.
小雏鸟来寻求母亲的安慰
But she has already made her choice.
但是她已经做出了决定
Only her first-born will get a drink.
只有第一个出世的宝宝能喝到水
Shoebills very rarely raise more than one chick.
鲸头鹳一般一次只抚养一只雏鸟
The younger chick was only ever an insurance,
小点的雏鸟只是个备胎罢了
in case the elder didn't make it.
以防大的不幸夭折
Now it's old enough, the adults know that
现在雏鸟都大了 成鸟知道
they're better off putting all their efforts
最好还是把所有精力
into bringing up just one fit and healthy youngster.
都用在抚养一只健康的幼鸟身上为好
The swamp's changing water levels
沼泽水位飘忽不定
mean fishing is too unpredictable
捕鱼全靠运气
for them to gamble on trying to raise two chicks.
所以一次抚养两只雏鸟风险太大了

重点解释

Shoebills very rarely raise more than one chick.鲸头鹳一般一次只抚养一只雏鸟

more than超过；多于

This city has a population of more than 1,000,000.

这个城市人口超过一百万。

I'll stay here not more than three days.

我将待在这里最多不超过三天。

The younger chick was only ever an insurance,in case the elder didn't make it.小点的雏鸟只是个备胎罢了以防大的不幸夭折

in case万一，以防；如果

I have kept a reserve fund in case of accidents.

我已筹备了一笔准备基金以防不测。

They watched him closely in case he should escape.

他们严密监视他，惟恐他会逃脱。

they're better off putting all their efforts最好还是把所有精力

better off情况更好

He will be better off in hospital.

他住院留医的话，病情定会好转。

He'd be better off going to the police about it.

他最好把这件事报告警方。