Great blue herons are able to hunt day and night, thanks to their excellent vision. It’s sometimes said that they need bright moonlight for nocturnal hunting, but the high density of rod type receptors in their eyes give them excellent night vision. They can and do hunt successfully on moonless nights.
One of my trail cameras captured a great blue heron hunting at night on two occasions. On one of those nights, there was only a sliver of a moon. Check out the video below. The info strip at the bottom of the video shows the moon phase for each night.
This camera was not stationed for heron activity, so it was a nice surprise to capture this and learn about its nocturnal hunting habits. I had actually hoped to capture the activity of a muskrat, which I had noticed was using the base of the snag (at left in the photo) as a feeding platform. The muskrat never showed, and it remains on my capture list.
Black, B. B. and M. W. Collopy. “Nocturnal Activity of Great Blue Herons in a North Florida Salt Marsh.” Journal of Field Ornithology. 53 (1982): 403-406.