Do all bird species lay unfertilized eggs? Some? A few? Just one?

[Frylock]

Domestic chickens lay eggs, if I understand correctly, every day, fertilized or not. Is this true of birds generally? Or is it something particular just to domestic chickens? Or is it something some birds do but not others?

[Broomstick]

Well, don't know about all birds, but I can confirm that parrots can and do lay infertile eggs. Well, at least the female ones do.

[Gatopescado]

Not all hens lay every day. They can suddenly quite for a while, and start again without notice. Depends on the season, the feed, weather. Pretty undependable creatures around here.

I can tell you there is nothing more depressing than buying chicken feed and eggs during the same trip to town.

Its my wife's gig.

[FluffyBob]

Damn chickens. The hens we had were prolific, pretty much an egg a day per bird for several years. Always amazed me. Those girls kept up a good appetite and went through a fair amount of crushed oyster shells on the side.

You would think it would be a very inefficient process to be favoured by natural selection. I am surprised parrots do it also.

[Enola Gay]

My brother's pet cockatiel lays eggs, though only seasonally (in spring/summer).

And my hens lay every day, as long as I remove the eggs and don't let them accumulate. If 8 or so eggs pile up, she'll stop laying and sit on them. I know that hens in climates that get cold stop laying in the winters. I think it has to do with temperature or hours of daylight or maybe both.

And FluffyBob, I don't think it's an inefficient process at all. In the wild, there is a male in the picture, so the hens are laying fertilized eggs that become the next generation.

[WhyNot]

Originally Posted by Enola Gay

My brother's pet cockatiel lays eggs, though only seasonally (in spring/summer).

And my hens lay every day, as long as I remove the eggs and don't let them accumulate. If 8 or so eggs pile up, she'll stop laying and sit on them. I know that hens in climates that get cold stop laying in the winters. I think it has to do with temperature or hours of daylight or maybe both.

Hours of daylight. Bright light (sunlight or a 60 watt light bulb) is needed for stimulating the pineal gland, between their birdy little eyes. Before electricity, eggs were a spring equinox beginning treat, which may be why they are a part of so many cultures' springtime holidays.

http://smallfarm.about.com/od/farman...inter_coop.htm

[RealityChuck]

Originally Posted by FluffyBob

Damn chickens. The hens we had were prolific, pretty much an egg a day per bird for several years. Always amazed me. Those girls kept up a good appetite and went through a fair amount of crushed oyster shells on the side.

You would think it would be a very inefficient process to be favoured by natural selection. I am surprised parrots do it also.

It evidently worked out very well for the species: chickens are extremely successful.

It's the same for navel oranges: both developed a trait that seems on first glance to be counterproductive, but which, due to interaction with humans, worked out by well.

[Filbert]

All birds *can* lay infertile eggs, though in most species they don't do it very often, at least in the wild. Normally, there's a series of environmental triggers (which can include stuff like nest building and pairing, as well as day length and temperature) that stimulate the release of eggs in wild birds, but this can misfire sometimes, or fertilisation can be unsuccessful, despite mating.

Pet birds of several species are known to lay even when kept singly, others will sometimes form a pair with another female, fulfilling the environmental triggers needed, and both will lay in a shared nest (and they keep sitting for ages, it's both funny and depressing to watch). No other species lays as many eggs as domestic chickens though- that is, after all, what they were selected for- even the wild ancestors of chickens, Jungle fowl, won't lay more than about 20 eggs a year tops, during the breeding season, and normally will only lay about 6 eggs- one normal sized clutch- in the year.

Other domesticated species kept for eggs, such as quail, and some ducks, can also produce pretty impressive numbers of infertile eggs, but chickens have a much longer history of selection, and are still the most productive.

[Pyper]

Anecdotally: Turtles also lay unfertilized eggs. Our pet box turtles got together and produced some baby turtles. The male was subsequently packed off to live in spoiled bachelorhood with family friends, but the female continues to lay eggs every year.

[Kobal2]

Originally Posted by FluffyBob

You would think it would be a very inefficient process to be favoured by natural selection.

I very much doubt natural selection had much to do with it . Domesticated species have been quite thoroughly re-engineered by man on just about every level.

[Bozuit]

I'm not sure how one can look at a chicken and think of natural selection.

[Max Torque]

Originally Posted by Kobal2

I very much doubt natural selection had much to do with it . Domesticated species have been quite thoroughly re-engineered by man on just about every level.

No doubt. Chickens are yummiest when they're young, so it's to the farmer's advantage to weed out the poor layers early. If one chicken only produces half the eggs of another chicken for the same amount of feed, that poor performer is slated to become a "young broiler/fryer". The good layer gets to grow old, breed, and eventually become a "stew chicken" when she's old and tough. So, by weeding out the poor performers, farmers will 1) save the money it would cost to feed an inefficient chicken, and 2) send a desirable young chicken to market. With the top performers as the only ones left to reproduce, the next generation gets a little more efficient at laying.

[Ulfreida]

Originally Posted by Max Torque

No doubt. Chickens are yummiest when they're young, so it's to the farmer's advantage to weed out the poor layers early. If one chicken only produces half the eggs of another chicken for the same amount of feed, that poor performer is slated to become a "young broiler/fryer". The good layer gets to grow old, breed, and eventually become a "stew chicken" when she's old and tough. So, by weeding out the poor performers, farmers will 1) save the money it would cost to feed an inefficient chicken, and 2) send a desirable young chicken to market. With the top performers as the only ones left to reproduce, the next generation gets a little more efficient at laying.

Maybe it worked this way long before the industrialization of chicken meat and egg production. The chicken you buy wrapped in plastic at the grocery store has been bred for meat and meat only, and is weeks, not years, old. It never got anywhere near old enough to lay an egg. The eggs you buy in styrofoam cartons are produced by hens who have been bred solely for maximum egg production for hundreds of generations. They have almost no meat on them. They lay nonstop under lights for a year and then are ground up into chicken meal.

Homestead, family-flock chickens are usually 'dual purpose' breeds (lay eggs pretty well and have some meat on them too). The cockerels are killed at a couple months of age while the hens typically lay for two to five years before they are stewed.