# Birds - egg production **URL:** \ **Category:** Factual Questions\ **Created:** [August 21, 2018, 3:57pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985 "2018-08-21T15:57:16Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![x-ray\_vision](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/x-ray_vision/32/351_2.png) [@x-ray\_vision](https://boards.straightdope.com/u/x-ray_vision)\ **Post date:** [August 22, 2018, 5:41pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/21 "2018-08-22T17:41:04Z")
> [@Riemann](#): > > …as meaning something _other_ than artificial selection, i.e. selective breeding for desirable traits within the range of natural genetic variation. I’m not sure what it could be taken to mean other than that. [Tim@T-Bonham.net](mailto:Tim@T-Bonham.net) seems to understand that. His objection to me answering with “no” seems to be based on non-domesticated birds also producing unfertilized eggs. It seems he thought my answer of “no” means that I think otherwise- that I think non-domesticated birds never produce unfertilized eggs. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [August 22, 2018, 5:57pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/22 "2018-08-22T17:57:02Z")
One of the things we didn’t focus on earlier was a good point that HoneyBadger made, > [@HoneyBadgerDC](#): > > …In most natural settings a male would always be present so evolution had no reason to discern whether or not a male was present. It could well be true that this weakens selective pressure in the wild, but I’d remain skeptical that it’s enough to remove selection pressure altogether. A fully-formed bird egg seems like a big energy expenditure relative to the size of a bird, so I think there would be significant selection pressure to avoid wasting that energy even if it’s rare for ova to remain unfertilized in the wild. ---
**Author:** ![x-ray\_vision](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/x-ray_vision/32/351_2.png) [@x-ray\_vision](https://boards.straightdope.com/u/x-ray_vision)\ **Post date:** [August 22, 2018, 6:09pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/23 "2018-08-22T18:09:02Z")
> [@Riemann](#): > > It could well be true that this weakens selective pressure in the wild, but I’d remain skeptical that it’s enough to remove selection pressure altogether. A fully-formed bird egg seems like a big energy expenditure relative to the size of a bird, so I think there would be significant selection pressure to avoid wasting that energy even if it’s rare for ova to remain unfertilized in the wild. As you say, it’s rare, as most wild birds lay eggs only during breeding season. That rareness seems to have been enough to not have birds wiped out due to the inability of having eggs become mostly developed only after being fertilized. I don’t think there’s any better answer than that. From the last paragraph in the first link: > [@](#): > > The next question is perhaps, “Why do chickens lay unfertilized eggs at all?” The reason is that the egg is mostly developed before being fertilized. The chicken cannot know in advance whether the egg will end up fertilized or not, so it just has to go ahead and grow the egg in the hopes that it will be fertilized. In the wild, this system works well because mating among fowls is common and most eggs do end up fertilized. ---
**Author:** ![x-ray\_vision](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/x-ray_vision/32/351_2.png) [@x-ray\_vision](https://boards.straightdope.com/u/x-ray_vision)\ **Post date:** [August 22, 2018, 6:56pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/24 "2018-08-22T18:56:37Z")
> [@Riemann](#): > > Discarding a single cell doesn’t waste the energy required to form a bird’s egg. My question arose because of that energy requirement. But a bird’s egg can be thought of as single cell (whether on not some would say the yolk or germinal disc is). ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [August 22, 2018, 7:05pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/25 "2018-08-22T19:05:36Z")
> [@Jonathan\_Chance](#): > > I have some young zebra finches. One of the females laid about 7 eggs over the course of a week or so. None developed. I’m told it was because she was so young - only a few months old - and the next clutch might develop. > > Seems weird to me. But other species aren’t required to function according to my lack of knowledge. I had a pair and the female kept laying eggs and chucking them out of the nest. I would find them on the floor of the cage. Eventually she began to lose feathers because of the stress of producing eggs constantly. Sometimes signals just get crossed up, especially in captivity, and animals do maladaptive things. > [@x-ray\_vision](#): > > But a bird’s egg can be thought of as single cell (whether on not some would say the yolk or germinal disc is). You’re still missing the point. The cost of producing or losing a mammalian egg is trivial. A bird has invested a large amount of energy in the egg, particularly the yolk, so laying an infertile one is far more costly. ---
**Author:** ![x-ray\_vision](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/x-ray_vision/32/351_2.png) [@x-ray\_vision](https://boards.straightdope.com/u/x-ray_vision)\ **Post date:** [August 22, 2018, 7:13pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/26 "2018-08-22T19:13:25Z")
> [@Colibri](#): > > You’re still missing the point. The cost of producing or losing a mammalian egg is trivial. A bird has invested a large amount of energy in the egg, particularly the yolk, so laying an infertile one is far more costly. Are you sure? Or have you maybe missed my point? My point is that an egg is already a single cell. How can the bird evolve to have it less developed before being fertilized is my point. I am aware of the nutrition contained in an egg. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [August 22, 2018, 7:35pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/27 "2018-08-22T19:35:19Z")
> [@x-ray\_vision](#): > > Are you sure? Or have you maybe missed my point? My point is that an egg is already a single cell. How can the bird evolve to have it less developed before being fertilized is my point. I am aware of the nutrition contained in an egg. Female birds are capable of storing sperm in the reproductive tract, and eggs can be fertilized up to 15 weeks after mating. So it would theoretically be possible for birds not to add yolk to the ovum until after it had been fertilized. ---
**Author:** ![x-ray\_vision](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/x-ray_vision/32/351_2.png) [@x-ray\_vision](https://boards.straightdope.com/u/x-ray_vision)\ **Post date:** [August 22, 2018, 8:59pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/28 "2018-08-22T20:59:18Z")
> [@Colibri](#): > > Female birds are capable of storing sperm in the reproductive tract, and eggs can be fertilized up to 15 weeks after mating. In wild birds? Cite? What about when the sperm doesn’t last nearly as long? Counting on that is a a better reproductive strategy than the rare laying of unfertilized eggs? > [@](#): > > So it would theoretically be possible for birds not to add yolk to the ovum until after it had been fertilized. Add yolk to the ovum? So the germinal disc would just be hanging around and it would attach to yolk that gets injected later somehow, and survive fertilized in the mean time? Germinal discs form ON yolks. The ovum with its yolk moves down the oviduct right after fertilization and the yolk provides nourishment immediately. I don’t see how anything you’re saying is “theoretically” possible, other than that being synonymous with “if everything about birds were different, it would be possible.” Great. What I actually hear you saying is “I’m not going to admit that maybe your point was valid.” [Previous page](https://boards.straightdope.com/t/birds-egg-production/819985.md?page=1)