Why , then , do fairy wrens succeed in spotting the infiltrator just 40 % of the time ?

那么，为什么鹪鹩成功地发现侵入者只有40%的时间吗？

The scientists identified ' urban adapters ' as crows , wrens and tits which all come from the same family and all have larger brains compared to their bodies .

科学家们发现，像乌鸦、鹪鹩和山雀等同科的“城市生活适应者”，它们都有着和自身体型相比更大的大脑。

Blue fairy wrens have testicles 25 % their body weight .

蓝鹩莺的睾丸重量占身体总重的四分之一。

A wren : researchers identified ' urban adapters ' as crows , wrens and tits which all come from the same family and all have larger brains compared to their bodies

一只鹪鹩：研究者们发现，像乌鸦、鹪鹩和山雀等同科的“城市生活适应者”，它们都有着和自身体型相比更大的大脑。

This trial and error has a chance of success because , in order to avoid too many false negatives , parent wrens will give chicks a number of attempts to get the tune right before abandoning the nest .

这个试验和错误里暗含着一个成功的机会，为了避免过多的假阴性，鹪鹩家长在放弃鸟巢之前，会努力教授雏鸟获取正确的鸣叫声。