[katieHaylor (OP)]

David asks:

How does a Cuckoo manage to lay an egg in its host nest that looks almost identical to the rest of the eggs in the nest? What biological processes would be involved in the mimicking of the host eggs?

Can you help?

[evan_au]

You could start here: https://en.wikipedia.org/wiki/Cuckoo#Brood_parasitism

[charles1948]

David asks:

How does a Cuckoo manage to lay an egg in its host nest that looks almost identical to the rest of the eggs in the nest? What biological processes would be involved in the mimicking of the host eggs?

Can you help?

The biological  processes  seem straightforward.   All birds' eggs are the same physical shape, ie, ovoidal.  They differ only in having shells with varying superficial markings on them. Like different colours, spots, speckles, and so on.   These superficial markings would be possible for a cuckoo to imitate. Such imitation is not unprecedented in nature.

 As for example,  in the case of chameleons and octopuses. These creatures, when they observe a nearby object with a particular colour or pattern, can send nerve impulses to their skins.  Making their skins generate a colour and pattern to mimic the observed object..

Therefore, what about this explanation:

 A cuckoo perches on the edge of another bird's nest. The cuckoo observes blue-shelled eggs lying within the nest. This observation sends nerve impulses to the cuckoo's ovary glands.  The glands respond, by generating eggs which
 mimic the blue shells.  Then the cuckoo, in due course, when the eggs are ready, lays  them in the other bird's nest.

Sounds plausible, don't you think?

[evan_au]

The cuckoo observes blue-shelled eggs lying within the nest. This observation sends nerve impulses to the cuckoo's ovary glands.  The glands respond, by generating eggs which
 mimic the blue shells.

I see a few problems with this hypothesis:
- Pigments in eggshells are produced by proteins, which are produced by genes encoded in the mother's DNA. Nerve impulses don't tend to rewrite DNA.
- The article on cuckoos suggest that the eggs have been fully formed, and incubated internally by the cuckoo for a day before she finds a nest of freshly-laid eggs. She doesn't see the nest and instantly repaint the eggs to match.
- I understand that there are different species of cuckoo which prey on birds of particular species. The cuckoos follow birds of this species to find a nest of eggs that are a good colour match to their own eggs.

But the good news is that this is a testable hypothesis. Show eggs from a random species of bird to a cuckoo, and see if it can reproduce the colour scheme!

I suggest that you at least read Wikipedia before you produce a hypothesis to lay in our forum:

Parasitic cuckoos are grouped into gentes, with each gens specializing in a particular host. There is some evidence that the gentes are genetically different from one another.

Taking a quick peek and producing something similar doesn't work very well (in nests or a forum).

[Bored chemist]

Show eggs from a random species of bird to a cuckoo, and see if it can reproduce the colour scheme!

Just a thought...
https://en.wikipedia.org/wiki/Cadbury_Creme_Egg