Carlos Delgado (Own work) [CC BY-SA 4.0]

The secret message of birdsong

如果没有鸟鸣声充满空气，春天将不一样。然而，尽管我们的耳朵愉快，但对于鸟儿本身，这些歌曲是严肃的事。在春季繁殖季节，这首歌在标志着领土和吸引女性的春季季节至关重要。

Why do female birds so often choose their mate by his song? The assumption is that a male’s song acts as a signal of his quality; in this sense birdsong acts in the same way as a peacock’s tail or the ability of a male deer to best its rivals in combat. A bird with a good song is advertising its superiority over males with lesser singing abilities.

在孔雀和鹿等物种中，男性对育儿的唯一贡献是为精子提供的，女性与最好的男性所获得的好处必须完全间接；也就是说，为他们的后代提供更好的基因。然而，在大多数鸣禽中，男性为父母护理做出了贡献，女性可能会选择雄性，这些男性会为养育年轻而做出更多贡献。

一个合理的假设，但是证据已经混合在一起。少数研究与鸟类的歌曲质量和父亲表演联系在一起（例如sedge莺），，，，but other studies (for example inpied flycatchers）不支持这一理论。

New research on nightingales, led by康妮·巴茨（Conny Bartsch）FreieUniversitӓt柏林和published today在BMC进化生物学，，，，provides some of the strongest evidence yet that a male’s song is an honest signal of their ability to raise chicks.

夜莺的歌

夜莺以其歌曲而闻名。这不仅归功于男性在夜晚唱歌的异常习惯（因此是名字），而且由于他们的唱歌的纯粹复杂性：一个单身男性可以将超过180多种不同的元素结合在一起，例如哨声，颤音和嗡嗡声。夜莺长期以来一直因其唱歌，鼓舞人心的诗人和莎士比亚，济慈和T.S Eliot等作家的美丽而受到钦佩。

The evolution of such complexity strongly suggests that the song is acting as a signal of male quality. This is especially true as males vary considerably in the size of their singing repertoires; some males are better singers than others.

While we still do not fully understand how female nightingales judge male songs,有证据那个女性在选择男性交配时判断单个歌曲的组成部分。反过来，这表明男性歌曲的复杂性与它们对饲养小鸡的贡献之间可能存在联系。

为了检验这一假设，研究人员研究了德国波茨坦的一群夜莺，这些夜莺已经受到了多年的监测。在整个繁殖季节都追踪了二十名男性，可以通过腿上的戒指来识别。

Firstly, the songs these males sang early in the season were recorded and analysed. The researchers focused particularly on the number of song elements (like buzzes and whistles) used and the orderliness of the song (i.e. the ability to repeatedly sing the same sequence of song types).

Later, once the males had mated with a female and the chicks had hatched, the feeding rate of each male (based on how often they visited the nest) was tracked across several days when their chicks were aged between 5 and 12 days old (a crucial time for the growing chicks).

好歌手，好父亲？

第一个关键结果是，二十位男性的喂养率确实有很大差异，范围从平均每小时七次访问，一个小时内到达近20次访问。有些男性比其他男性更好。

Did their songs predict who would be a good father? Indeed they did: there was a strong correlation between the complexity and orderliness of a male’s song and his feeding rate. This was true even when accounting for how many chicks each male had to feed.

尤其，先前的研究has shown that older males sing more orderly songs; this might suggest that these males have greater experience of raising chicks and finding supplies of food in these breeding grounds. This provides one possible link between song quality and parental skills.

由于很难收集此类数据，研究人员无法确定雄性喂养率对小鸡大小和生存可能性的影响。目前尚不清楚女性如何应对伴侣的努力差异。女性可能会增加自己的喂养努力，以在某种程度上弥补贫穷父亲的失败。相反，在其他鸟类中，雌性已被证明在creasetheir own feeding efforts when mated with what they perceive to be a good male.

无论哪种方式，男性的努力肯定对他的小鸡幸福至关重要。与所有鸣禽一样，许多夜莺小鸡在巢穴中仍会饿死，而对于那些确实离开巢穴的小鸡，他们的体重和状况对于他们的第一个冬天生存的机会可能至关重要。鉴于此，如果雄性通过歌曲来表明自己作为未来父亲的质量，则有明显的进化原因是女性在此基础上不断发展伴侣。

从Aristophanes和Virgil到Keats和Shelley，夜莺长期以来一直被用作诗人的象征。然而，我们发现夜莺的歌不是爱情的绝妙姿态。它的歌是一首诚实的歌，呼吁其能力做艰苦的工作来提高下一代。如果只有同样的话，我们人类彼此宣告的每一个爱情宣言……

And below, a video of a male feeding his chicks – remember, the best fathers are heroically doing this up to 20 times an hour. Audio and video clips courtesy of Conny Bartsch.