I've shot them with a .22-.250 in the past. Starling scattered at the shot--scattered in a 25ft. circle that is!
I don't know if a starling is worse than a city pigeon (disease-wise) pigeons (like rats) have been known to carry 30+ different diseases (now that's a bird with a hell of a punch!) but they ARE nasty! For example, an English sparrow will keep its' nest somewhat tidied up and clean---not a starling! They crap anywhere and everywhere, including their nests! In the early 60's, Milan, Michigan went through an epidemic of cholera impacting grade school children from one particular school. It was found that huge flocks of starlings were landing and roosting in the schoolground trees. Of course, they left their droppings all over the place and the children, playing in recess time, got infected.
Farmers hate starlings because of the cholera from their droppings wiping out complete lots of hogs and livestock, not to mention ruining the roofs of their barns.
Anyone who loves song birds recognize the starling as a pest. Starlings kill the young of song birds and push away song birds from feeders.
If you want to have some fun, get yourself a crow tape/CD and play it full blast. Starlings, blackbirds and jays will come as though they heard the Pied Piper I kid you not! I've called the three in out in the middle of a woods, close to barns, you name it. From what I've seen, they come in to this sound at least as well as crows. Heck, I remember one that I missed two times with a .22 Long Rifle and he just stayed in that tree transfixed by the sound!;0) It was like he was hypnotized or something until the 3rd shot ended his trance for good!
A buddy of mine who does pest control work has used starling decoys for years. He takes some cardboard and cuts out pre-traced starling shapes, spray paints them and uses portions of wire hangars to serve as legs. He says that they work very well.
A very quiet airgun is about as good as it gets. Something like a Beeman R-7 in .177 is about perfect because of its' superb accuracy and extremely quiet report. My friend uses one and he says that he even uses a dome pellet too because a flat head will make enough of an impact sound on a hit bird that will (needlessly) spook other birds in a flock (starlings can be very spooky.
Although I do agree with my friend on the spring-piston airgun, I have also had alot of success using a .22 rimfire with CB caps and subsonic LR's (solids and hollowpoints) depending on the ranges involved.
Regarding cats and starlings, I've been told that alot of cats will NOT eat a starling. Check it out maybe but not eat it. If that's the case, I'd say that cats CAN be smart at times!;0)