After a couple of minutes, and several near misses, I finally caught the cat before she caught the bird. I carried her into the house (and she absolutely hates being picked up) where she is now, making plaintive mews that are intended to coax me into letting her back out. Not until the birds have bedded down, kitty! I hope the fledgling can make it back into the nest. If it's stuck on the ground all night, well, mine isn't the only cat who prowls around here. Of course, in the wild there would be nobody to protect the bird, or the mice, or other small creatures, from the cats, and if there were, then the cats- at least those who weren't eaten by still larger creatures- would starve. My well-fed kitty is part of a short-circuited corner of nature. She doesn't need an infant avian snack.
By coincidence, Peter Bogdonovich's movie "The Cat's Meow" is on IFC now. I think I'll go watch it. I'll get extra sound effects.