American Robin building nest. Original public domain image from Flickr
A nest is more like a crib than a home: It is used exclusively to protect eggs and raise young, and every species has its own unique way of constructing nests to meet the challenge. But how does a robin know how to make a robin nest? If you would guess it's an instinct, then you are right, but what a complex instinct! It begs the question, how much else is instinct? Does a bird know why it sings; why it mates; what is going to hatch out of those eggs? By extension, how many of our "choices" are just instinct? Are there any choices?! Does free will even exist?! This is how birding takes one down the rabbit hole. Credit: Michael Schramm/USFWS. Original public domain image from Flickr