Here’s a photo from the Galapagos story that didn’t make it into the book, but I still enjoy.
In order to attract a mate, male frigates make a nest on the ground or in trees and then put on a show by inflating the pouch on their throat while calling out and spreading their wings. Clearly bigger is better when trying to impress the ladies flying overhead. I am amazed at how inflated they get these. It looks like they could pop.