I had an idea to make cockatrices "realistic" (as in make a bit more sense) for what ever reason the noble cockatrice has evolved to use other species eggs for its own. It does this by "sitting" on usually a chickens egg. When it does this it inserts it's own embryo into the egg.

The cockatrice embryo proceeds to eat the chicken embryo and uses the nutrients in the egg to gestate. Once it gestates the cockatrice would scamper away into the wilds.

Would a parasitic embryo like this work? Could a cockatrice replace a chicken's embryo with its own?

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    $\begingroup$ Good question, I should think an answer might need to take into account any inherited immune system (or just plane reservoir of antibodies) that a minimally developed chicken could have access to in ovo, protecting any punctture of the shell and membranes in the replacement process - re-sealing the egg to prevent infection...... etc. $\endgroup$ Commented Apr 23, 2019 at 14:36
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    $\begingroup$ Why not go the cuckoo and replace the eggs with its own. birds are not terribly good at recognizing foreign eggs. $\endgroup$
    – John
    Commented Apr 24, 2019 at 16:31

3 Answers 3


The tachinid flies have a similar mechanism when parasitising butterfly eggs:

Illustrative genera include: Exorista, Voria, and Plagia. Many Tachinid eggs hatch quickly, having partly developed inside the mother's uterus, which is long and often coiled for retaining developing eggs. However, it is suggested that the primitive state probably is to stick unembryonated eggs to the surface of the host.[7]

From Wikipedia's article on Tachynidae https://en.m.wikipedia.org/wiki/Tachinidae

Despite the distant common origins of flies and butterflies, the parasite feeds well off the egg content of the host butterfly.


I'm by no means sure of this, biology is not my wheelhouse, but I would think that the most likely "solution" in this case is that the Cockatrice reproduces by introducing a live-born predatory infant into the eggs of prey species. This tiny creature then burrows into the shell, attaches itself to the inside to seal the egg and halt evaporation and then simply kills and eats the chicken embryo and grows inside the shell using it as protective camouflage almost like a hermit crab until it has developed sufficiently to fend for itself.

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    $\begingroup$ Plausible for a neophyte and perfectly gross. Have my +1 $\endgroup$
    – Nyakouai
    Commented Apr 23, 2019 at 14:54
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    $\begingroup$ Nice idea - sharks kick off young, why not cockatrices: livescience.com/29198-shark-embryos-cannibalize-others.html $\endgroup$ Commented Apr 23, 2019 at 15:00
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    $\begingroup$ Lots of wasps and flies do exactly this. $\endgroup$
    – Willk
    Commented Apr 23, 2019 at 15:09
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    $\begingroup$ @Willk Yeah that was where my thinking was at, I just thought that sealing a shell after egg implantation was more problematic than a slightly more mature parasite that does the job itself. $\endgroup$
    – Ash
    Commented Apr 23, 2019 at 15:11
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    $\begingroup$ Perhaps, re-sealing the shell is possible only because it is a cockatrice, whose glance, touch, or breath could be said to be capable of sterilization. $\endgroup$
    – Mazura
    Commented Apr 24, 2019 at 5:08

Cockatrice is hatched from a cock egg, incubated by a toad.

Now, "cock egg" could mean one of two things:

  1. Egg actually laid by a rooster (male)
  2. Malformed egg

Neither allows possibility of cockatrice using a regular egg that would hatch a chicken if not disrupted. Both of those mean that cockatrice has to affect the bird before the egg is laid. In fact, it doesn't even have to be an actual egg, it merely has to be something that people can mistake for an egg. A parasitic cockatrice could develop in a living chicken, and then leave it in a form of a spore. The spore is something that resembles an egg. If it leaves the chicken through cloaca, it would be almost impossible to tell if it's excreted or laid - hence the rooster part.

The toad part is harder to make up an airtight explanation for. A spore could be activated by a toad (which is lured by mimicking it's pheromones), then "hatches" and the toad is young cockatrice's first kill.


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