Fathering in the Bird World

In the bird world, once mum has laid that egg, dad can legitimately sit on that egg. And that is worth something. This is why we do see a lot of by parental care in the bird world. I fee like the best example, or the first time i kind of became aware of a bird parenting was that penguin documentary. As they move about, the fathers will balance their eggs like tight toos. You saw these amazing emperor penguins passing an egg back and forth between themselves to keep it warm. Yes. It does beg the philosophical question of, how does a cuckoo bird know it's a Cuckoo bird if it was raised by a magpi?