After a week or so of looking, and hundreds of miles on the new Subaru, I finally found a merlin this afternoon—in a favorable location for trapping, and just a few miles from home. I deployed a phai trap baited with a sparrow, then a short distance away dropped two more sparrows in a bal-chatri, and finally parked and settled in to wait.
Seemingly out of nowhere—actually from between two buildings—came a passage redtail intent on the sparrow fluttering in the phai. Almost immediately, a spike kestrel (no idea where he came from) made a slashing stoop at the redtail, but the bigger bird continued undeterred and took the sparrow, mauling the lightly-built (but fortunately weighted) phai in the process; she managed to carry the trap and weight over a chain-link fence before being grounded for good. Cursing, I sprinted around the fence to release the redtail as the kestrel departed for points unknown. The redtail was caught in a single noose, and once I'd draped her in my overshirt (good thing it was a cool day, as I have been wearing just T-shirts) it was easy enough to let her go—but what a show for the merlin.
I carried the mangled phai back to the car and drove off, hoping against hope the merlin might still hit the bal-chatri. To my surprise, she hadn't flown off straight away.
Instead, she scanned the area from her lightpole for ten minutes, and then flew away.