The warbling white-eye is a non-native bird that was introduced to the Hawaiian islands from Japan in the 1920s and '30s. Over the last century, they've become the most abundant bird in the entire state.
From a distance, you might mistake a mejiro for a native 'amakihi, as both birds have olive-green plumage. However, the mejiro has a distinctive white circle around its eye, to which it owes its name.