Most people assume that roosters are programmed to crow at the first sign of sunlight to announce the dawning of a new day, or some such romantic notion.
大多数人都会认为每当第一缕阳光照耀大地，公鸡就会按规律打鸣表示崭新一天的开始ix~c#r]IUnZ6nW。除此之外还有很多关于此浪漫的传说P3s,GDU#UN^H^XcCh6。
Like all birds, roosters call in a daily cycle determined by circadian rhythms.
和其他鸟类一样，公鸡每天打鸣的习惯是由生理节律所决定._oyOp+6.S4aW。
That is, a rooster's internal clock allows it to anticipate the sunrise and prepare for another exciting day of looking for food.
公鸡的生物钟让它期待日出，以此为契机开始新一天的觅食kz*9g&5TQQq|un。

But why must roosters crow as they prepare to start their day, and why do some roosters sound off before dawn?
但是，为什么公鸡会打鸣，而且这一时间点是在黎明前呢？
Roosters are territorial creatures and don't much like other roosters trespassing on their land.
公鸡是具有领地意识的动物，决不许其它公鸡侵犯自己的领地.0OG9EjSKl。
They crow in order to establish their domain and warn other roosters to stay away or prepare to brawl.
为了守护自己的地盘，警告其它公鸡远离进而避免争斗+v4+0kD5FltcAttl5。
And because their internal clocks are sometimes set a bit early, some roosters begin crowing well before sunrise.
而且公鸡的生物钟有时候设置得早一些，所以有些公鸡是在日出前打鸣64yh9gGzNvDii1Gz]J^W。