Drat. I should have made a meal of these Oysters, but I've seen (toxic) Omphalotus olearius growing in very the same spot:
https://www.inaturalist.org/observations/236924747
These species are too similar for this novice to risk.
At least 5-6 of them seen along the dike.
At least 5 or 6 seen along dike between lakes.
Just as I was about to fall asleep, I heard the owl call. It called for around 30 minutes and it sounded like it moved at least once. Around 2:30 I saw it fly away.