Rück's Blue Flycatcher

Rück's blue flycatcher is a passerine bird in the Old World flycatcher family Muscicapidae. It is known from only four specimens and is endemic to a small area in northeast Sumatra, Indonesia, inhabiting primary lowland forest. Although all specimens share common characteristics, such as a black bill, brown iris, and black feet, two of the collected specimens show some physical discrepancy with the other two. They were initially described as Cyornis vanheysti before being accepted as specimens of C. ruckii. Rück's blue flycatcher has also been compared to other species of Cyornis.