Is it more humane to kill stray cats, or let roam and kill native birds?

I've been considering this depravity for at least two decades. An early (for me) disaster was finding a neighbor's house cat with a Song Sparrow in its maw. That happened in the borough of Conyngham, Pa., and the neighbor was just across the street from our home. I showed the dead bird to the woman of the household and she swore up and down that "her" cat would never have done such a thing. Of course, it does not matter one iota whether a free-roaming cat is hungry or not To kill prey is what felines strive to do. Here's a feature-length article about this ongoing debacle. Millions and millions of native birds are killed in North America each year by free-roaming cats.