So we were still left puzzled over what animal could have produced this pellet. Owls and hawks were out because the pellet was too large. Eagles were floated, but we don't typically see a lot of large eagles around here. So while possible...it didn't seem probable. Vultures were a good candidate, but we don't usually see them in the park, either. They like to hang out by the roads...to pick up all the roadkill.
Since we'd found it on the boardwalk by the pond, and because we'd seen great blue herons at the pond, it really felt like that was our best option.
But great blue herons are aquatic birds. Do great blue herons eat squirrels?
Yes. They. Do.
They just...swallow them whole.
Here's a video of a great blue heron hunting gophers:
And here's another video of a heron eating a squirrel (the background dialogue is pretty funny— "He's literally eating a squirrel!" "What do you want me to do about it?" "Is this...is this murder?"):