Delaware Living Will I Have A Small Blue Bird With A Black Head Living In A Bird House In Delaware. Size Of A Finch . Any Ideas?

I have a small blue bird with a black head living in a bird house in Delaware. size of a finch . Any ideas? - delaware living will

The bird house created in early May which has a blue background with white breast and a small black dot on his head. I wish I had an idea what it is.