How pretty! Maybe we'll put up a bluebird box this year. In the past the sparrows took over the box.

Link...

And most authorities simply show no mercy toward sparrows and starlings:

from UT:

Competition for available nesting sites is another apparent cause of Bluebird decline. The importation of exotic bird species has also affected the Bluebird nesting site availability. Bluebird have always been in competition with native species for nesting sites. Chickadees, nuthatches, wrens, and tree swallows are cavity nesters too and compete with the bluebird for any available hollow. But with the importation of the house sparrow in 1851 and the European starling in 1890 from Europe, competition for nesting sites reached a different level. House sparrows begin nesting early in the season and often take the nesting sites first. Starling do nest later in the season, but are so aggressive and larger than Bluebirds that it is a simple task for a starling to evict a nesting Bluebird from any nest the starling may want for themselves.
So where are the Bluebirds today? Come find them at the Arboretum. We have lots of them. Why? Because there are nesting boxes positioned in appropriate places and appropriate densities to encourage the rebounding population. The trick to prevent the starling from taking over the nest box. This is easy. The access hole in the box needs to be 1 ½ inches in diameter. The starling is to big to enter. Exit the starling. House sparrows are an altogether different problem. They can enter the small hole and must be cleaned out of the nest before they get established. This takes diligence where house sparrows are a problem.

Thanks, WC. :)

-- OneTahiti

Lovely pic!