I know @Shadrach wrote an article about the egg song being an escort call which I found really interesting. I'll have to reread it soon because most of the info has fallen out of my ears
So I don't remember if this was touched on in the article but I watched a video recently (I don't have the link) where the person stated that the egg song is an invitation for other hens to lay on her nest, so that she can incubate and hatch them.
The discussion of whether a hen will accept chicks that aren't hers reminded me of that. Does anybody have any thoughts on this?