Rück's Blue-flycatcher Cyornis ruckii


Justification of Red List category
This species has not been recorded since 1918, and no forest remains in the vicinity of its two known collecting localities, so it may have declined severely as a result of habitat destruction. However, it cannot be assumed to have gone Extinct, because lowland forest in Sumatra has been relatively poorly surveyed, and the specimens were collected in "exploited forest", hinting at a tolerance to some degree of habitat degradation. Any remaining population is likely to be tiny, and for these reasons it is treated as Critically Endangered.

Population justification
The population is assumed to be tiny (fewer than 50 individuals and mature individuals) based on a lack of records, despite searches, since two specimens were collected in 1917-1918.

Trend justification
Population trends are unknown and are thus not quantified.

Distribution and population

Cyornis ruckii is known from two specimens collected in 1917 and 1918, at Tuntungan and Delitua in the lowlands of northern Sumatra, Indonesia. Two further specimens are purportedly from Malaysia, but their provenance has been questioned. The species must have always been very rare or local, given the failure of all but one zoological collector to obtain specimens.


Its ecology is virtually unknown. Specimens were collected at 150 m and 200 m in "exploited forest", suggesting it may tolerate some habitat degradation. The fact that they were taken in January and April raises the possibility that the species may be migratory. Judging by its morphology, its closest relatives are to be found in the Hainan Blue-flycatcher C. hainanus group of China and South-East Asia: birds of tangled understoreys and secondary forest. However, as the species's taxonomic relationships remain unclear, a broad outlook should be maintained on its likely ecology.


There is apparently no remaining forest cover at the two known collecting localities (they are situated on the outskirts of a large city; Medan), and the species's range may therefore have shrunk considerably. However, the description of its habitat as "exploited forest" raises the possibility that it may persist in adjacent disturbed wooded areas.

Conservation actions

Conservation Actions Underway
CITES Appendix II. This species has been protected under Indonesian law since 1972. The Wildlife Conservation Society has actively tried to locate this species in the lowlands surrounding Gunung Leuser National Park, and although the current status of surveys are unknown, there is hope to expand this work in the future once additional funding has been secured (N. Brickle in litt. 2007).

Conservation Actions Proposed
Examine the two skins in detail to improve understanding of its taxonomic status, and indeed (by consideration of wing length) to determine the likelihood of its being migratory. Conduct surveys (including use of mist nets) for the species between January and April in remaining forest patches ranging out from the two historical locations. Develop a conservation plan for the species, pending results of these surveys, including the establishment of protected areas, where appropriate, at any sites supporting populations.


17 cm. Medium-large, blue flycatcher. Male mostly dark blue, becoming paler on forehead, rump and lower breast, white on belly. Slender, black bill and legs. Female has brown upperparts, becoming rusty on rump, tail and breast. Paler buff throat and belly. Similar spp. Male White-tailed Flycatcher C. concretus is larger, has paler blue forehead, fringes to wing feathers and distinct white outer tail feathers. Female has white on breast sides and tail sides. Male Pale Blue-flycatcher C. unicolor is paler blue with contrasting black lores. Female is duller brown on chest. Voice Undocumented. Hints Survey dense understorey habitat.


Text account compilers
Fernando, E.

Benstead, P., Bird, J., Brickle, N., Butchart, S., Davidson, P., Derhé, M., Khwaja, N., Symes, A., Tobias, J. & Verbelen, F.

Recommended citation
BirdLife International (2023) Species factsheet: Cyornis ruckii. Downloaded from on 28/09/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from on 28/09/2023.