Beitzah 7 - A hen and an egg
Let us start with a rule: any creature whose mating occurs during the day (like a chicken) gives birth during the day; one whose mating is at night (a bat) gives birth at night, and people and other similar creatures, who mate both by night and by day - they give birth both at night and during the day.
What practical lesson does this teach? The following: if one checked his coup before the Holiday (Yom Tov) and there were no eggs, and then he checked early in the morning and found an egg, he can eat that egg, because he can be assured that the hen laid it during the day - just that he missed it. But what if he checked really well? - Perhaps the egg came out only partially, and then went back - but it is still considered laid the day before the Holiday and is therefore permitted.
What about Rabbi Yose who says that the egg in such a situation is forbidden? - Rabbi Yose is talking about the egg that was not fertilized by a rooster, and which the hen laid by warming itself against the ground. But if the rooster is present - the hen will not do that and will wait for the rooster instead, so we can be sure that the egg is laid by day and consequently eat it.
How far can the rooster be? - Even sixty houses away, as long as the hen hears its crowing in the morning. However, if there is a river, the rooster will not cross, but if there is a bridge - he will. But not a bridge made out of rope. And yet, there was a incident when the rooster crossed the river over the bridge made of rope.
Art: Rooster with Hens and Chicks By Carl Jutz