This has bugged me for a while. Someone said, half jokingly, that hen’s eggs as found on the supermarket shelves are aborted hens. How is it that an egg pops out (or is made to pop out?) of a hen at such time that we find egg white and yolk, but no yucky chick foetus?
Is there a foetus waiting to grow inside every egg I see on the supermarket shelf only its been taken away from its mother so soon that it cools off and dies? I really have no idea and it seems strange. Coming from a small town, going to a rural school and having so many friends and customers of my father from the bank who were farmers, I suppose I should know really. The only time I visited a farm with the school , all we saw were small chicks running around looking all cute.
IIRC a woman in England buys Quail eggs in shops and incubates them at home to get any Quail inside to grow. Quite a few of them emerged from their eggs. How are they sold in shops if they’re so close to hatching?
Laying hens live a life of forced abstinence. In other words the eggs are infertile. Don’t know about the quail eggs, but I must assume that they are temp. controlled before selling.
They’re not fertilised; the bodies of domestic hens (and indeed some other birds, even in the wild) are geared up to egg production in such a way that it will pretty much happen regardless of the presence of a male to fertilise them.
Quail are different, I think, and will not lay eggs unless they’re actually trying to nest; the chick embryo in fertilised eggs of many species does not start to develop significantly until the eggs are incubated at the right temperature; up until that point, they can often be stored at room temperature for weeks.
This enables birds to lay a clutch of eggs, one per day, then start incubating them, to have them all hatch out at about the same time - if they didn’t do this, the first chick to hatch would have so much of a head start on the others, it would outcompete them for food and only the first-hatching chick would stand a good chance of survival.
BTW; if you check the photo gallery on my birdcam website (linked in my sig above), the same thing is documented there; the blue tits in my nest box produced one egg per day until there were ten; then the female started incubating them and they all developed and hatched within a few hours of each other, even though there was a ten-day gap between the laying of the first and last eggs.
I can answer your question, we raised chickens when I was a kid. The chicken eggs you buy in the supermarket are unfertilized. Mature hens lay an egg about once a day, whether there’s a rooster or not. If there isn’t one (and on modern commercial egg farms, there never are), the eggs will never hatch.
Ah, so unlike a human female who will just exude a small amount of material with its tiny egg, hens go the full hog and produce a fully sized egg, regardless of whether they’ve been fertilized.
Hen’s eggs are usually sold unfertilised. Hens lay anyway, and fertilised eggs don’t keep as long.
There is a Phillipines delicacy (Baalut) involving a fertilised egg with fairly developed chick inside, feathers and all. These would be rather well labelled, so fear not.
Absolutely right; the egg-production machinery (at least in chickens) just cranks out eggs; in the presence of a male, these would be fertilised, but either way, eggs are coming out.
With other birds (particularly smaller ones), egg-production is something that happens in response to specific stimuli, such as courtship and nesting behaviours.
My understanding is that laying of unfertilized eggs is a defect found to a varying degree in wild birds, and that prehistoric farmers selected for this defect when domesticating fowl, to the point where modern hens lay eggs with metronome-like regularity even if they never see a rooster. Is this correct?
Could well be; I think chickens have been domesticated for quite a long time; in that sort of circumstance, there are very often traits present that would not occur readily in the wild, or would even be disadvantageous to survival.
Selecting for it would be an interesting process though, because you’d have to decide to breed those individuals (i.e. pair them with a mate) that don’t require a mate to produce eggs; not impossible, but would be difficult to do unwittingly (as selection is thought to have occurred in other cases).
Unless it’s just a fortuitous side-effect of initial selection for greater egg production alone, in which case it could easily be selected for without a grasp of selective breeding (i.e. it could arise out of a decision to eat a chicken, but not the one that lays the most eggs).
Human females produce an infertile egg every month they have a period. Human eggs, once fertilized, are nourished inside the body. Birds eggs carry a yolk to nourish the embryo while it develops. If no sperm penatrate the egg, either in the woman or the chicken, the egg is expelled unfertlized.
Only cats, as far as I know, ovulate only when stimulated to do so by the presence of sperm.
“Defect” is subjective. I wouldn’t call any other co-dependent organism defective; it’s just co-dependent.
But indeed, in nature I would probably guess that producing an egg that couldn’t hatch as being a waste of resources. But fortunately for chickens, evolution is based on genetic randomness rather foreplanned logic.
I wouldn’t exactly call it a “defect.” As has been mentioned before, wild birds in general won’t begin to yolk up eggs unless there has been some appropriate stimulus, such as the presence of a male or courtship activity. (It is possible that some females may end up laying unfertilized eggs due to some defect of the reproductive tract even if they mate, or due to inappropriate mating behavior.) However, once they have started they will go ahead and lay the egg whether it has been fertilized or not. Domestic chickens no doubt have been selected so that they do not require outside stimulus to lay eggs almost daily.
Hens were not always kept in egg farms but used to run loose with roosters all around. A large percentage of the eggs were doubtless fertilized. If the egg isn’t incubated the embryo will not develop. The eggs were gathered and were either collected by a produce truck that drove through the country or taken to the market in town by the farmer. All eggs were candled to ensure that the embryo hadn’t developed. Occasionally an egg with blood in it would slip by the inspection process and was just discarded and the loss accepted by the user as part of the game.
The more I think about this, the more I realize how little I know about avian embryology. Somebody needs to tell me about the birds and the bees!
In the case of a wild bird, what does the egg look like at the point when it’s fertilized by the sperm? I had always pictured that the bird produces a small egg cell, not unlike a human, and then, if it’s fertilized, develops it into the big, yummy, yolky thing that we buy at Jewel. But it sounds from your post like big-egg development starts with courtship. How far does it get before mating and fertilization? Does the sperm have to penetrate the egg shell?
At what point does a fertilized, incubated egg become inedible? I assume that people started eating eggs by robbing the nests of wild birds (or reptiles or, in Australia, mammals). But I don’t know any culture that enjoys eating embryos; people want the yolk and the white. Is the trick in wild-egg eating to get the egg as soon as possible after it’s laid?
The George Carlin quote above touches on a misconception about eggs. That stringy part attached to the yolk at each end of the egg is not the developing embryo, even in fertilized eggs. It’s just connective tissue that keeps the yolk in the middle of the shell. The actual embryo, if you bought a fertilized egg, is a wee dark spot on the surface of the yolk.
Some people go out of their way to buy fertilized eggs and/or brown-shelled eggs in the belief that they are somehow more nutritious. They are not.
