This video shows a frantic bird battle that I observed in the Cleveland Metroparks in mid-May. I initially thought it was a trio of Eastern Bluebirds, with the male trying to court the female, while the was trying female trying to feed her young. But something looked off about the “young bluebird” sticking its head out of the nest box. So I shared the video on twitter, and some birders corrected me about what was happening. It turns out that the Eastern Bluebirds were trying to get a House Sparrow out of the nest box. House sparrows will kill other birds, including Bluebird nestlings. I did not stick around long enough to find out if the Eastern Bluebirds were successful ridding their nest of the invasive House Sparrow.
Things to notice in the video: