Carol,
Would not surprise me that a European Starling (EUST) could make it through Gilwood entrance. I have had them squeeze in 1 1/2″ round holes (actually may have been 1 9/16″). They can get in Peterson box oval holes no problem. Gilwood has that larger dimension at the top so could probably squeeze their shoulders right through. Did it have yellow bill – or partial yellow transition to breeding bill color? They are non-native and worse than HOSP for Purple Martins and woodpeckers…
