The Hoopoe is a very very weird bird. Naturally, it is one of my favourites. Among it’s many weird-ities: The female of the species lays the most beautiful cerulean eggs…and then proceeds to constantly paint them with her poop until they turn stinky and grey. The greyer and stinkier they get, the more the father appreciates the mother’s artistry and mothering skills and brings her more food, juicy fat lizards and beetles, ostensibly to encourage more sexy poop.
The science behind it is that the good bacteria from the mother protects the embryo from the outside pathogens. This is very similar to human babies who have a vaginal birth and hence get covered/ protected by the good flora present in the mother’s vaginal canal. Apparently these these days doctors introduce the vaginal flora of the mother to babies born through a c-section as well.
The weirdo Hoopoe always knew how important good poop is.