Well hey, time to draw the annual shellfire down upon my head
I maintain a 48 pair martin colony a public school campus, I have maintained this school colony since 1998 (??). I cannot recall the last time I killed a house sparrow. The reason I do not kill sparrows is because in the eyes of the school community "Mr. Scully killing birds." gets all the attention, rather than the martins. Plus the odd kid and their parent who are members of PITA.
No house sparrows breed in our colony.
What I have worked out is this.... clipping the tail feathers to the nubs with a pair of scissors and letting them go.
See, tails are rather important to house sparrows in various displays, like this male threatening a purple martin....
I catch them in a trap gourd, then with an ordinary pair of scissors trim their tail feathers to the nubs, clip the undertail covers (body feathers) to further obscure the normal sparrow shape, and let them go. They'll look like a ball with wings.
I must have done it sixty or seventy times now, it has worked every time. I've done it so often I can leave my classroom, lower the housing, grab the sparrow, clips its tail, let it go, raise the housing and get back to class all inside of a six-minute passing period
They may hang around the colony for a couple of days, but like Austin Powers they've lost their mojo. They don't LOOK like a sparrow to other sparrows, and the males cannot do their drooping wing/cocked tail courtship display. I am told it is also difficult for the males to copulate without the support of a tail.
Two caveats: 1) You have to get the sparrows before they are feeding young or else they will continue to feed their young and 2) Do not PLUCK the tail feathers. Plucking them stimulates rapid regrowth. In just two weeks that same sparrow will have a visible tail.
I know this because I see these same sparrows on campus for months, clipping tail feathers does not seem to seriously hurt their chances of survival.
Starlings are a different matter entirely. Starlings are absolute death on purple martins, ANY starling that breaches an SREH opening has to go.
We had two gourds with slightly opened SREH entrances up this year, my fault. Starlings got into both. I have devised a fast way to kill starlings that is even quicker than clipping a sparrow's tail (very important when time is limited and you have to be discrete):
Hold the starling with the back of its head under your thumb, bottom of the head of the starling braced against your index finger. Crush in the back of the skull with your thumb, its thinner than an eggshell.
I dispatched all four starlings this way this year. I REALLY hate doing it, but it needs to be done. All I can do is make it happen as fast and efficiently as possible. Tail-clipping doesn't work on starlings, and once I tried relocating one thirty miles away. The next day it came back, and killed a martin inside a gourd.
Mike
I'm in the country with a creek running thru it and wildlife pond of about an acre big. I have 65 acres. I have almost packed it in this year because I hate killing birds. Guess I'll just keep a pair of scissors in my back pocket.y 
