Eastern Bluebirds were in trouble by the 1950s due to loss of habitat and
the introduction of English sparrows (aka House Sparrow) in the late 1800s.
The Patuxent Research Refuge has a "Bluebird Trail"
which is more aptly called a "Songbird Trail".

This female Eastern Bluebird which nested in one of our boxes had all the food
it needed this year (the year of the 17-year cicada).