how do bird’s eggs retain enough heat to survive when their parents are not actively sitting on them?

Question

I’m sure some of it depends on the species of bird, but I still don’t get it.

In: Biology

Answer 1

Cavity-nesting birds lay eggs one day at a time, and may leave them for several days before they begin incubating instead of starting incubation immediately. Once they start, though, those embryos are developing and won’t survive if the mother disappears.