Sure enough, while mama mallard was on a constitutional, some less-than-upright individual vandalized the mama's nest.
She came back and laid a couple more eggs. As of this morning, she was still incubating.
The photographer has nicknamed mama mallard "Tulip." Interested parties have taken to leaving small cups of water and duck food for her.
Hopefully, Tulip's remaining eggs will hatch and the ducklings will safely make their way to the river a couple of blocks from her nest.

Mallard duckling doodle based on a photo by Flickr user Raj the Snapper.