I’m sure some of it depends on the species of bird, but I still don’t get it.
In: Biology
It’s not going to kill the egg if the temperature drops a bit. It will slow down development slightly, but not very much. The alternative, having to be incubated 100% of the time, had a much worse outcome.
If a parent bird could never be able to go feed, poop, drink water, etc. Very few species of bird will feed each other on the nest. Most birds can’t take turns, as males are adapted to defend a territory (securing food resources).
A parent might be able to store up enough fat to actually accomplish a week or two of sitting on the nest, but it would leave them unable to feed their newly-hatched chick, they would waste away while incubating.
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