There's a really nasty concoction called Tanglefoot that's intended to keep insects off of fruit trees that birds absolutely loath.
It has the consistency of thick honey, and it stays extremely sticky for a long time.
Just be careful how you handle it because of its extreme tackiness.
Rubber gloves and a spatula of some sort that you don't mind parting with are highly recommended.
btw...I have used Tanglefoot by smearing it at the entry/exit points for buildings, smearing it all the way around the hole, then had my brother spook starlings out through the hole from inside the building, while I stood right below the hole with my air rifle at the ready.
When those nasty starlings try to make an escape through the holes, they get the Tanglefoot on their wings, and unable to fly, drop like rocks.
It's no problem at all to pick them off with an air rifle then, or even by hand (gloves required, naturally because of that gooey Tanglefoot) by simply grabbing them and wringing their necks.
They make a product that comes in tube for a caulking gun for birds.. I will check on the name for you...if its starlings you can make a trap.. PVC pipe (3-4") a elbow and a trash can with a lid... starlings will be drawn to any hole and investigate.. take the pvc pipe and cut a 2' length,put on the elbow add a 3'-4' piece.. take your trash can (55 gallon drum works great) cut a hole in it the size of your pipe insert pipe and secure so that it is about half way down from the bottom. Fill with about 10" of water and let the bird bath from HE** do its job...
Pigeons and sparrow's - rice with barley and some sugar works well too.. they eat it and it swells in them. = death... Works OK. I vote for the pellet gun and a chair.. good luck.