Oriental Cuckoo Cuculus optatus


Taxonomic note
Previously treated as a subspecies of Cuculus saturatus (del Hoyo & Collar 2014), C. optatus is split once more following Xia et al. (2016) who showed that these are two vocally distinct taxa after a previous paper had suggested they were undifferentiated in voice. Score 4 for the difference (3?4 notes vs 2 = a 50?100% increase) in voice, plus 2 for difference in size (optatus male wing mean 218.4, saturatus 183.4: Erritzøe et al. 2012: 469?470), 1 for slightly broader black barring on chest to belly which extends to vent. Name horsfieldi used for Palearctic populations, but this has been shown to be inappropriate and name optatus reinstated (Payne 2005). This taxonomic concept was previously recognised between 2006 and 2014 following Payne (2005). Prior to that treatment, C. lepidus (Payne 2005, del Hoyo & Collar 2014), C. saturatus and C. optatus had been included within C. saturatus following Sibley and Monroe (1990, 1993). Monotypic.

Taxonomic source(s)
Handbook of the Birds of the World and BirdLife International. 2021. Handbook of the Birds of the World and BirdLife International digital checklist of the birds of the world. Version 6. Available at:
Payne, R. B. 2005. The cuckoos. Oxford University Press, Oxford, U.K.

IUCN Red list criteria met and history
Red List criteria met
Critically Endangered Endangered Vulnerable
- - -

Red List history
Year Category Criteria
2021 Least Concern
2016 Not Recognised
2014 Not Recognised
2012 Least Concern
2009 Least Concern
2008 Least Concern
2007 Least Concern
2004 Not Recognised
2000 Not Recognised
1994 Not Recognised
1988 Not Recognised
Species attributes

Migratory status full migrant Forest dependency medium
Land mass type Average mass -

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 24,700,000
Extent of Occurrence non-breeding (km2) 26,100,000
Number of locations -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 500000-5000000 poor inferred 2021
Population trend decreasing inferred -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) 1-10 - - -
Decline (10 years/3 generation past and future) 1-10 - - -
Number of subpopulations 1 - - -
Percentage in largest subpopulation 100 - - -
Generation length (yrs) 3.7 - - -

Population justification: Densities of 0.1-0.5 singing males/km2 have been recorded in Russia (Hagemeijer and Blair 1997). Assuming an equal sex ratio and 20-40% occupancy of its EOO breeding range, the population size is suspected to number 500,000-5,000,000 mature individuals; the true figure is likely to be at the highest end of this estimate given that the European breeding population is estimated at 120,000–155,000 calling or lekking males, or 240,000–310,000 mature individuals (BirdLife International in prep.). National population estimates include: c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in China; c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Taiwan; c.100-10,000 breeding pairs and c.50-1,000 individuals on migration in Korea; c.100-100,000 breeding pairs and c.50-10,000 individuals on migration in Japan and c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Russia (Brazil 2009).

Trend justification: Remoting sensing data on tree cover lost indicate that c.6-8% of forest cover has been lost from the species's breeding range over the past three generations (11 years; Global Forest Watch 2021). Its reliance on undisturbed forests for breeding is unknown but the majority of its host species are moderately forest-dependent, and the present species is reported to be outcompeted by C. cuculus in more open habitats in parts of its range (Erritzøe et al. 2012). Forest loss may be anticipated to accelerate with forest fires in Siberian forests becoming more frequent (and intense) as a consequence of climate change. This should continue to be monitored closely. Forest loss is occurring at a similar rate (5-7% over three generations) in this species's non-breeding range, which may equally be causing some decline; however, this species has been noted wintering in open and heavily degraded habitats, and so these declines are thought to be less significant. Overall, the species is suspected to be declining at a rate of 1-10% over three generations.

Country/territory distribution
Country/Territory Presence Origin Resident Breeding Non-breeding Passage
Australia extant native yes
Cambodia extant native yes
China (mainland) extant native yes yes
Finland extant native yes
Indonesia extant native yes yes
Japan extant native yes yes
Kazakhstan extant native yes
Kyrgyzstan extant native yes
Laos extant native yes
Malaysia extant native yes
Micronesia, Federated States of extant native yes
Mongolia extant native yes
Myanmar extant native yes
New Zealand extant vagrant
North Korea extant native yes
Palau extant native yes
Papua New Guinea extant native yes
Philippines extant native yes
Russia extant native yes
Russia (Central Asian) extant native yes
Russia (European) extant native yes
Solomon Islands extant native yes
South Korea extant native yes
Taiwan, China extant native yes
Tajikistan extant native yes
Thailand extant native yes
USA extant vagrant
Vietnam extant native yes yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Artificial/Terrestrial Plantations suitable non-breeding
Artificial/Terrestrial Rural Gardens suitable non-breeding
Artificial/Terrestrial Subtropical/Tropical Heavily Degraded Former Forest suitable non-breeding
Forest Boreal major breeding
Forest Subtropical/Tropical Moist Montane suitable breeding
Forest Subtropical/Tropical Moist Montane suitable non-breeding
Forest Temperate major breeding
Shrubland Temperate suitable breeding
Shrubland Temperate suitable non-breeding
Altitude 0 - 4500 m Occasional altitudinal limits  

Threats & impact
Threat (level 1) Threat (level 2) Impact and Stresses
Biological resource use Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest] Timing Scope Severity Impact
Ongoing Minority (<50%) Negligible declines Low Impact: 4
Ecosystem degradation
Natural system modifications Fire & fire suppression - Increase in fire frequency/intensity Timing Scope Severity Impact
Ongoing Minority (<50%) Negligible declines Low Impact: 4
Ecosystem degradation, Reduced reproductive success

Recommended citation
BirdLife International (2023) Species factsheet: Cuculus optatus. Downloaded from on 06/06/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from on 06/06/2023.