Remove all dead Starlings from the area and out of view, and they 'll fly in for a bite. Other dead Starlings make them very nervous.
They will also stay in the trees if there is activity around the neighborhood, or noises coming out of the house, etc. depending how close the cat food is from the house. The farther from the house the faster they come in and are not as nervous, but you have to position it where you feel comfortable you can make a kill every time.
Sometimes they have already eaten and are just waiting to get hungry again. I have seen them stay up in the trees for a whole hour and then descent and eat everything within a minute. If they know you are watching, or they spot you, even from 35yds out, that will prevent them from coming down too. Mine usually land at the very top of 2 of my trees in the back 35-40yds out. They can stay there for 1-1.5hrs before coming down, especially if one of the shades is half way up (and I haven't noticed it) or when we are up in the morning getting my son ready for school. Once things quiet down, and all the shades are down, windows closed, etc. they will one by one come down and go after the bait. Concealment is #1 with Starlings and crows, but I am sure you know that. You 've already gotten a bunch
