A bird has built a nest on a beam sticking out from the back of our shed. She's laid several beautiful blue eggs. Every time one of us passes through the back yard the mother bird flies from the nest and settles on a nearby branch.
Imagine her situation: children to incubate, but terror of these enormous creatures that occasionally lumber by. When the creatures arrive she is compelled to flee, yet compelled to stay near and watch over her eggs. Of course my wife and I are no threat to her eggs, but we know of no way to reassure her.
Afraid to stay, unable to leave. I'm incubated from such fragile circumstances, but I suppose it's the norm for most creatures, including many humans.