Five North American neotropical migrant passerines have been documented breeding in western Mexico on their southbound migration. It is the first time North American nocturnal migrants have been documented breeding during a migratory stopover. Fascinating.
I read about this a few days ago and was stunned by the implications. It truly is an amazing adaptation and makes me want to visit the thorn forests of Mexico!
It makes you how many other species may do this as well, and maybe even the chance of some sort of secret nesting going on amongst winter visitors in the Amazon! It would make protecting wintering grounds as paramount as protecting breeding areas.