Prothonotary Warblers are cavity nesters. The males, like this one, build several nests and then sing to attract a female who finishes one of the nests.
B’s work boots live just inside the garage when they are not working. This Prothonotary Warbler seems to be considering the merit of this as a nest site. He disappeared in first one boot and then the other, before following his nose in search of a less odiferous location than sweaty work boots.
As many snakes and skinks as we have, this was probably not a good idea, anyway.
Just one more reason to dump your boots before you put your foot in.