After over a week of eluding my careful sweeps, I finally managed to spot the eldest St. John the Diving fledgling. Despite her superior camoflauge, her very active hunting style gave away her location. In the space of about 30 minutes, I watched her kill and consume two mice and also try to snag a careless squirrel. Here's a video of her ambush!
After consuming her lunch, she flew to a large oak tree where I was able to get some decent shots!