CR

Cyornis ruckii

Local name: Rück's Blue Flycatcher

Unknown

Overview

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.

Rueck's Blue Flycatcher faces severe population decline primarily due to extensive deforestation and habitat degradation across its limited range in Southeast Asian lowland forests. The species' specialized requirements for primary forest understory make it particularly vulnerable to logging operations and agricultural conversion. Mining activities and infrastructure development have further fragmented the remaining suitable habitat, while the bird's restricted range amplifies the impact of these localized threats.

Threat summary

Habitat

Rueck's Blue Flycatcher inhabits the understory of primary and mature secondary lowland tropical forests, typically below 500 meters elevation. The species shows a strong preference for dense forest interior with minimal human disturbance, requiring intact canopy cover and rich insect populations.

Forest· major

Conservation measures underway

Site/area protectionSpecies managementSpecies recoveryLegislation

Other threatened species in MUSCICAPIDAE

VU

Humblot's Flycatcher

Humblotia flavirostris

Declining
VU

Little Slaty Flycatcher

Ficedula basilanica

Declining
VU

Izu Robin

Larvivora tanensis

Stable
Javan Blue FlycatcherCR

Javan Blue Flycatcher

Cyornis banyumas

Declining

Threatened in Indonesia

EN

Speckle-faced Bent-toed Gecko

Cyrtodactylus psarops

Unknown
Acropora hemprichiiEN

Acropora hemprichii

Declining
VU

Bacan Myzomela

Myzomela batjanensis

Declining
VU

Hopea coriacea

Declining

Frequently asked questions

Why is Rück's Blue Flycatcher classified as Critically Endangered?
Rück's Blue Flycatcher is classified as Critically Endangered — facing an extremely high risk of extinction in the wild — because population sizes are very small, declining sharply, or restricted to a tiny range. Rueck's Blue Flycatcher faces severe population decline primarily due to extensive deforestation and habitat degradation across its limited range in Southeast Asian lowland forests. The species' specialized requirements for primary forest understory make it particularly vulnerable to logging operations and agricultural conversion. Mining activities and infrastructure development have further fragmented the remaining suitable habitat, while the bird's restricted range amplifies the impact of these localized threats.
Where does Rück's Blue Flycatcher live?
Rück's Blue Flycatcher occurs in Indonesia, and Malaysia. Country-level distribution data is sourced from the IUCN Red List and cross-referenced with GBIF occurrences.
What are the main threats to Rück's Blue Flycatcher?
The main threats to Rück's Blue Flycatcher are ai-1, ai-2, ai-3, and ai-4. The full IUCN-classified threat record for this species is detailed on the species page.

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