Bluebird And Nuthatch Fighting Over House

Q: We setup a bluebird house in our rain garden. White-breasted nuthatchs
went in and out for a few days. Then the bluebirds showed up. Today the
nuthatch is going in and out. Did the bluebirds just give up? Is this scenario
normal? 
A: Nuthatches and bluebirds prefer similar size nests so they fight over any
appropriate housing. Bluebirds are bigger than nuthatches so they usually win,
but not always. Be sure your entrance hole is 1 1/2 inches in diameter; this is
what bluebirds prefer. Nuthatches like a smaller opening of 1 inch wide.
Whichever bird occupies your nest, know that you are contributing to needed
ecological diversity in your landscape.