I’m sure some of it depends on the species of bird, but I still don’t get it.
In: Biology
Eggs in a next are left alone very little if at all, with most species if birds. They can go a few minutes, even hours, without a parent setting, but not much, not often.
What that means is the mom and dad just stay on the nest, night and day, take turns, etc. until they do hatch. Hunger, cold, and danger be damned.
They don’t. That’s why penguins and other Arctic birds pretty much stay on the eggs 100% of the time unless transferring to the other parent. The ambient temperature being warm enough allows other birds to not sit on the eggs as often in warmer climates.
I keep poultry and egg sitting is interesting. When a bird is “broody,” meaning they are sitting on eggs, their normal day to day activities stop. They get up to drink, ducks will bathe, but then it’s right back to the eggs. If there is food readily available and nearby, they will eat it but they won’t go looking for food.
Many birds raise their young at a time of year when there’s not a danger of immediate death to the embryos if the mom gets up for 10-15 minutes, and artificial incubation protocols often incorporate this (recommendations for incubating duck eggs often include taking the heat off for 10 minutes a day and misting the eggs with water, for instance, simulating a mother duck coming back to the eggs with a damp breast).
Both temperature and humidity are factors in successful incubation, and mass has to be lost from the eggs through evaporation to leave an air pocket of appropriate size to facilitate hatching. The eggs being exposed to the air every day is part of how that happens
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.
On the flip side from some of the other comments, eggs can continue to survive without heat for a decent period of time depending on the age of the embryo.
We had an incubator when I was a kid- used it yearly. We had several hundreds chickens.
One year the power went out about 2.5 days prior to the hatching date. We got the power back on and all the eggs hatched- no issues even though they were room temp for at least 24-36 hours.
Having inconsistent heat and humidity prior to the “almost hatched” stage will result in a lot of issues with thyroid, death, and a bunch of limb deformities.
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.
I am an avian biologist and my experience has been different than most of what I am reading here. The birds species I work with share incubation duties- plenty of species do that. And they regularly take breaks from the nest, esp on cooler days. They are extremely attentive when it is very hot and will constantly incubate or shade the eggs (the cutest is when they will get their breast feathers wet and shade the eggs while dripping water on them). We have had eggs get flooded or buried and if it is within a day or so until they are recovered, those eggs can often still be viable. Colder weather or that situation will slow them down and they hatch a little later than we expect, but they do make it. Too hot def seems a bigger an issue, and the birds seem to know it.
this is actually part of the plan. the short cool down of the eggs can improve the chance of hatching healthy. i even read something about how different organs in the embryos won’t develop properly without the slight cool period they get from being left alone for a bit. hen gets to go peck around for a bit. and her kids get functioning livers. crazy evolutionary stuff.
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