Mystery flycatchers in Sumatra - Rück's Blue-flycatcher or White-tailed Flycatcher?

Abstract

Observations, photographs and a sound-recording taken in Jambi, Sumatra, in 2013 and 2014 refer to a pair of unidentified flycatchers with certain characters that match some features of Rück's Blue-flycatcher Cyornis ruckii. However, a review of alternative possibilities cannot exclude and indeed tends to favour White-tailed Flycatcher C. concretus, given that (i) the white breast-patch of the female and white tail-markings of the male can remain hidden, (ii) the female can be strikingly rufous in some light or some individuals, and (iii) the white belly patch seems to exclude ruckii. The sound recording has no match in sound archives and the song recorded might have involved infrequently heard phrases used in courtship. Nevertheless, new searches of the undisclosed site are planned, and new searches in any remaining tracts of primary lowland forest on Sumatra are urged.