If I build a house it is considered a man made structure. (let's make it out of logs and mud)
If a bird builds a nest it's nature.

But why can't it be natural for me to build a house?

(I've had too much thinking time today! )

Maybe we should call nests 'bird made structures'!

That's a very good question Copago!

Do human beings have an instinct to build huts, houses and the like - or do they merely have an instinct to seek shelter? Most adult human beings don't don't have the know-how to build even a plain hut, unlike adult birds with their mysterious ability to build nests.

Then of course your average bird doesn't install plumbing and electricity.

Question--is it natural for birds to have "nest eggs" or is that man made?