Nesting in creatures

One thing that comes to mind with eggs are nests. In the series creature nests are interestingly missing. Critters do have nests, but none for norns, ettin and grendels. A relatively simple agent could add them, but in what way or form?

Nests are often enough legacy structures which generations of birds building upon the last, as do bees and ants. Of course it is completely possible that the nests of creatures have disappeared since the shee have left, but new nests would be a mass of several nests given how communal creatures often are.

Of course the creatures are domesticated in a way and perhaps nesting instincts would have been bred out in the lore, but in nature something like nesting are necessary.

Mechanics for nests

The nests could produce homesmell, speed up incubation and perhaps slow the decay of eggs if such decay has been added. An increase of warmth perhaps too. The important thing would be the way they would be created. To simply place them from the agent injector would do little for immersion, so creation would need to be by creatures themselves.

The triggers for building them would be intense homesickness, pregnancy and perhaps an abundance of eggs and food.

Would there be other requirements? An amount of raw materials in the form of detritus, food or plant material, though a norns understanding would likely be too lacking.

Other structures

If nests are a possibility, then where do you draw the line? With every generation nests become more complicated. If you look to weaver bird- or harvest mouse nests, these already look like treehouses. Would several generation old or highly populated ettin nests become anthill like constructs, or grendel nests decomposition heated natural incubators?

Would granaries be a possible or sensible structure, machinery or entertainment? 

Would it serve a purpose?

The nest would at the very least add immersion. It would also create clear points of interest, and be more likely to come into existence at busy places. As these nests would offer benefits these places would be more likely to remain occupied. 

I personally think it would slightly inhibit travel, but granaries or entertaining totempoles would do so even more if a high enough drive would trigger their creation. This way an empty room would very quickly become a village. The whole idea clearly needs more balancing, but to me at least the idea is fun.

What do you think?