Male Eastern Bluebird looking at his reflection in a mirror. The male Eastern Bluebird (Sialia sialis) is a medium-sized thrush found in open woodlands, farmlands and orchards. Its bright blue plumage, easily observed on a wire or open perch are territorial during breeding. The males will challenge their reflection on windows and other reflective surfaces when they consider it a threat.They are cavity nesters producing typically between two to four broods during spring and summer (March through August in the Northeastern United States). Spring. Ludlow, MA. USA. Wild.