Carol, this box is inch and a half, its a Nature’s Way box, but it does have some wear on the edges.
Lucky box for me, last year it fledged a total of 9 birds (in two sets of course!)
I think the only boxes i have up now that have larger entrance holes is the Peterson they are nesting in now, i believe that is 1 9/16 inch and elongated.
I’ve thought of putting up a box with a large entrance hole and nestbox trap just specifically for trapping starlings.
V/r,
Chris