One of the sages, R’ Ishmael the son of Satri’el, testified before R’ Judah the Nasi about unique events which had happened in his place of residence. Once a very large cedar fell; 16 wagons traveled across its length, side by side on its circumference. He also said that once a large bird, the bar yuchni dropped its egg while in flight. The contents of the egg, white and yolk, caused a flood and flooded 60 great cities and broke 300 cedars. The scholars asked: It is inconceivable that the bird would drop its egg while flying, for birds do not customarily do that. We can deduce this from what is written in the Scriptures: “The wings of the renanim Ne’ElaSaH” (Job 39:13). Renanim is the bird which the sages called bar yuchni. Ne’ElaSaH is an acronym for Noseh [carries] Oleh [rises] niSHatei [goes down]. This implies that the bird, when it wants to lay its egg, goes down to the ground and carefully lays the egg so it will not break, but does not lay eggs while flying. Answer: The rare event which the sage testified to above involved an unfertilized egg, and thus the bar yuchni dropped it while flying because it would never hatch a chick and so there was nothing to fear by its breaking. The Scriptures imply that it does not lay its egg while flying, but carefully lays the egg on the ground; this is what happens only with a fertilized egg.
(Babylonian Talmud, Tractate Bechorot 57b)