I don't think it is reliably true no. I have heard a number of variations on the temp determining sex by killing one or the other. But think about it. If this was a reliable method for ensuring you only got pullets to hatch, don't you think the big hatcheries would be using it all the time? Out of the fridge eggs I hatched last month I'm pretty sure I have a fairly even mix of pullets and cockerels. I don't know for sure of course, but there are pretty good signs.Is that true!? What is the science behind that? That would be cool.![]()