# 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:** 20\ **Page:** 1
**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 21, 2018, 3:57pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/1 "2018-08-21T15:57:16Z")
I’m a molecular/evolutionary biologist rather than a zoologist, and I was mocked recently for my ignorance in supposing that domestic egg-laying chickens might require the presence of a rooster. Evidently they do not - they usually produce an egg every day, even if there’s no rooster around. It seems that my understanding of reproduction in _actual_ birds and bees is incomplete. What happens with wild birds? Making a bird egg requires a huge energy expenditure, so surely it can’t be the case that unfertilized ova in wild birds routinely develop into fully-formed unfertilized eggs? Is this just a trait that we have bred into domestic chickens? ---
**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 21, 2018, 4:09pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/2 "2018-08-21T16:09:33Z")
Wild birds will sometimes lay unfertilized eggs. I wouldn’t say it was “routine.” It happens rarely, when something goes wrong with mating or the fertilization process. It can be a problem since the bird will continue to sit on them even though they will never hatch, preventing it from starting a new fertile clutch. ---
**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 21, 2018, 4:11pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/3 "2018-08-21T16:11:01Z")
> [@Riemann](#): > > Is this just a trait that we have bred into domestic chickens? Yes. > **[Why did evolution create a chicken that lays so many unfertilized eggs when...](https://www.wtamu.edu/~cbaird/sq/2013/11/21/why-did-evolution-create-a-chicken-that-lays-so-many-unfertilized-eggs-when-that-is-so-wasteful/)** > > Natural evolution did not create a chicken that lays so many unfertilized eggs. Human engineering created such chickens. You could call the process... ---
**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 21, 2018, 4:15pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/4 "2018-08-21T16:15:08Z")
Thanks both of you. The article x-ray linked to is exactly what I couldn’t find to confirm this. At least I don’t feel like I was being dumb now. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [August 21, 2018, 4:19pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/5 "2018-08-21T16:19:47Z")
I had a parakeet (budgerigar) that laid unfertilized eggs. I don’t remember exactly how many but there were at least 6 or so over the course of several months. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 21, 2018, 4:20pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/6 "2018-08-21T16:20:31Z")
> [@x-ray\_vision](#): > > Yes. > > [Why did evolution create a chicken that lays so many unfertilized eggs when that is so wasteful? | Science Questions with Surprising Answers](http://wtamu.edu/~cbaird/sq/2013/11/21/why-did-evolution-create-a-chicken-that-lays-so-many-unfertilized-eggs-when-that-is-so-wasteful/) Quail do this, ducks do this, turkey’s and many others. What triggers them to stop laying is when they get enough eggs to form a clutch, this may vary from chicken to chicken. As long as we keep removing the eggs they will keep laying. I think there ability to cover and incubate the eggs might play into how large of a clutch they lay. In most natural settings a male would always be present so evolution had no reason to discern whether or not a male was present. ---
**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 21, 2018, 4:24pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/7 "2018-08-21T16:24:45Z")
> [@markn\_1](#): > > I had a parakeet (budgerigar) that laid unfertilized eggs. I don’t remember exactly how many but there were at least 6 or so over the course of several months. > [@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. Perhaps it’s also sensitive to the availability of ample food. ---
**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 21, 2018, 4:32pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/8 "2018-08-21T16:32:07Z")
> [@HoneyBadgerDC](#): > > As long as we keep removing the eggs they will keep laying. Not at the rate that thousands of years of selective breeding allows for nor for the total amount of eggs hens are born with. ---
**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 21, 2018, 4:37pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/9 "2018-08-21T16:37:39Z")
Interestingly, [turkeys have been found to be capable of producing offspring parthenogenetically from unfertilized eggs.](https://ferrebeekeeper.wordpress.com/2011/05/16/turkeys-and-parthenogenesis/) Through a quirk of bird genetics, all offspring produced this way are male. Unfertilized chicken eggs can sometimes start to develop parthenogenetically, but development stops once the eggs are incubated, so no young are produced. ---
**Author:** ![snowthx](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snowthx/32/10660_2.png) [@snowthx](https://boards.straightdope.com/u/snowthx)\ **Post date:** [August 21, 2018, 8:42pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/10 "2018-08-21T20:42:56Z")
> [@HoneyBadgerDC](#): > > Quail do this, ducks do this, turkey’s and many others. What triggers them to stop laying is when they get enough eggs to form a clutch, this may vary from chicken to chicken. As long as we keep removing the eggs they will keep laying. I think there ability to cover and incubate the eggs might play into how large of a clutch they lay. In most natural settings a male would always be present so evolution had no reason to discern whether or not a male was present. Here is my question: How does the bird stop laying eggs? What is the trigger? It sounds like something not under conscious control, but something biological. It’s not like they can think “Oh, this is enough eggs for now, I will stop laying”, is it? ---
**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 21, 2018, 10:17pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/11 "2018-08-21T22:17:38Z")
> [@snowthx](#): > > Here is my question: How does the bird stop laying eggs? What is the trigger? > [@](#): > > Broodiness is due to the secretion of the hormone prolactin by the anterior lobe of the hypophysis. Prolactin injection in hens provokes egg laying to stop within a few days, vitellum reabsorption, ovary regression (hens only have a left ovary[14]) and finally broodiness > **[Broodiness](https://en.wikipedia.org/wiki/Broodiness)** > > Broodiness is the action or behavioral tendency to sit on a clutch of eggs to incubate them, often requiring the non-expression of many other behaviors including feeding and drinking. Being broody has been defined as "Being in a state of readiness to brood eggs that is characterized by cessation of laying and by marked changes in behavior and physiology". Broodiness is usually associated with female birds, although males of some bird species become broody and some non-avian animals also sho In wi... > [@](#): > > 1. How is a broody hen different from a non broody egg laying hen? > > The normal cycle for any egg laying hen is that for about an hour beforehand, she experiences a “hormonal surge” (Kimberly Willis and Robert Ludlow) that makes her find a nest. Once she has found the nest, they prepare it by turning round and round to shape it- dogs do a very similar thing on their beds. After they have laid an egg, with the hormones receding, the hen will stay still for a few minutes before getting up. [http://www.allaboutchickens.info/broody-hens-guide/](http://www.allaboutchickens.info/broody-hens-guide/) ---
**Author:** ![snowthx](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snowthx/32/10660_2.png) [@snowthx](https://boards.straightdope.com/u/snowthx)\ **Post date:** [August 21, 2018, 11:07pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/12 "2018-08-21T23:07:21Z")
Thank you, **x-ray vision**! Ignorance fought! ---
**Author:** ![Enola\_Gay](https://avatars.discourse-cdn.com/v4/letter/e/3ab097/32.png) [@Enola\_Gay](https://boards.straightdope.com/u/Enola_Gay)\ **Post date:** [August 22, 2018, 12:12am UTC](https://boards.straightdope.com/t/birds-egg-production/819985/13 "2018-08-22T00:12:34Z")
We have backyard hens (no rooster), but I thought I’d add that broodiness varies from hen to hen. We have one who gets very broody after a clutch of 2-3 - she sits on the eggs, refusing to leave the nest & won’t even let us remove them, so we have to do it at night. While other hens will ignore a clutch of 6-8 eggs & range all day. Not sure if this is due to genetics or just differences in personality. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 22, 2018, 12:52am UTC](https://boards.straightdope.com/t/birds-egg-production/819985/14 "2018-08-22T00:52:44Z")
> [@snowthx](#): > > Here is my question: How does the bird stop laying eggs? What is the trigger? It sounds like something not under conscious control, but something biological. It’s not like they can think “Oh, this is enough eggs for now, I will stop laying”, is it? I think it may have something to do with their body being able to cover all the eggs, when it feels like they have reached the limit if eggs they can cover I suspect they stop laying. As said above some of them will stop and sit at 3 or 4 eggs. ---
**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, 2:56am UTC](https://boards.straightdope.com/t/birds-egg-production/819985/15 "2018-08-22T02:56:33Z")
> [@HoneyBadgerDC](#): > > I think it may have something to do with their body being able to cover all the eggs, when it feels like they have reached the limit if eggs they can cover I suspect they stop laying. As said above some of them will stop and sit at 3 or 4 eggs. Different species of birds lay anywhere from one to more than a dozen eggs in a clutch, so that’s not it. Most likely, there is a hormonal trigger that tells a female to stop laying after the typical clutch size is complete. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [August 22, 2018, 4:16am UTC](https://boards.straightdope.com/t/birds-egg-production/819985/16 "2018-08-22T04:16:08Z")
> [@Riemann](#): > > Is this just a trait that we have bred into domestic chickens? > [@x-ray\_vision](#): > > Yes. No. We have extended this trait by selective breeding, but it was there already. Non-domesticated birds also produce unfertilized eggs, just not as often. And it occurs in other species, too. Human females, for example, produce an egg every month, whether fertilized or not (discarded via menstruation). ---
**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, 4:30am UTC](https://boards.straightdope.com/t/birds-egg-production/819985/17 "2018-08-22T04:30:37Z")
> [@Tim\_T-Bonham.net](#): > > No. > We have extended this trait by selective breeding, but it was there already. Non-domesticated birds also produce unfertilized eggs, just not as often. I’m not sure what you mean by “no” - what did you imagine we were talking about other than artificial selection? > [@Tim\_T-Bonham.net](#): > > Human females, for example, produce an egg every month, whether fertilized or not (discarded via menstruation). Discarding a single cell doesn’t waste the energy required to form a bird’s egg. My question arose because of that energy requirement. ---
**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, 5:19pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/18 "2018-08-22T17:19:10Z")
> [@Tim\_T-Bonham.net](#): > > No. I guess it depends on one’s view on what “routinely” means within the bounds of what the OP was asking (considering selectively bred domestic hens lay year round and tens of times the amount of wild fowl, which lay primarily in spring) and his mentioning an energy expenditure by the hen. Based on his response, my interpretation resulted in him getting the info he was looking for. As was mentioned in the first reply by Colibri, the majority of eggs laid by wild birds will be fertilized. Also, your responded with “we have extended this trait by selective breeding, but it was there already” doesn’t take into account my “no” response regarding the factors I just mentioned. However, the information in my link is correct. Whether or not I should have prefaced with a “yes” or “no” is subjective. ---
**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, 5:32pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/19 "2018-08-22T17:32:07Z")
> [@x-ray\_vision](#): > > …Whether or not I should have prefaced with a “yes” or “no” is subjective. Well, it depends on interpreting the question that I asked… > [@Riemann](#): > > Is this just a trait that we have bred into domestic chickens? …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. ---
**Author:** ![Jonathan\_Chance](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jonathan_chance/32/701_2.png) [@Jonathan\_Chance](https://boards.straightdope.com/u/Jonathan_Chance)\ **Post date:** [August 22, 2018, 5:37pm UTC](https://boards.straightdope.com/t/birds-egg-production/819985/20 "2018-08-22T17:37:37Z")
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. [Next page](https://boards.straightdope.com/t/birds-egg-production/819985.md?page=2)