String Them Along

I'm trying some new with my two bird houses this spring, see below.

There is always a battle between my beloved Eastern Bluebirds and the dreaded, annoying Sparrow to determine who gets to claim these bird houses as home.

What I've been doing, which is so counter productive, is I block the holes.  However, I only do this when the sparrow have taken over but inevitably it also prevents the bluebirds from moving in too.

I recently read on one of the social media apps that hanging string like I've done below wards off sparrow and most birds, as they flap their wings as they approach and enter the hole.  However, bluebirds do not, rather they swoop in with their wings closed.

Remember you can't believe everything you read on social media, so we'll see if there's any validity to this approach.  I'm not sure if I've installed the string properly but I'll keep a close eye and adjust if I need to.  At the end of the day, if this approach deters the sparrow I'll consider it a win.  I loath those god awful, noise and messy birds, GRRR!