Right as we were getting ready to leave for Sunday dinner with Andy's family, I heard Andy say downstairs, "There's a heron on the back lawn!" I came flying down the stairs, grabbed the good camera, and snuck out the front door and around the house.
Lo and behold, this Yellow-crowned Night Heron was hunting bugs on our lawn. That first shot is just after he swallowed a worm he grabbed from the dirt (hence the grass and dog hair on his bill in the photos). Their info entry on All About Birds suggests that they mostly eat crabs, of which we have plenty on our riverbank, but they do also forage for terrestrial bugs, which this fellow was doing.
He eventually flew up into a tree, which I took as a sign that I had gotten as close as I could without spooking him, so I quietly backed up around the house and slipped inside.