• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Turbott, E.G. 1990. Checklist of the Birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	C2a(i)	A2ce+3ce+4ce; C2a(i)

Red List history

Year	Category	Criteria
2022	Endangered	C2a(i)
2016	Endangered	C2a(i)
2013	Endangered	C2a(i)
2012	Endangered	C2a(i)
2008	Endangered	C2a(i)
2006	Endangered
2004	Endangered
2002	Endangered
2000	Vulnerable
1996	Vulnerable
1994	Vulnerable
1988	Near Threatened

Migratory status	not a migrant	Forest dependency	high
Land-mass type		Average mass	-

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	199,000 km2	medium
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	1500-2499 mature individuals	good	estimated	2021
Population trend	decreasing	medium	inferred	2013-2029
Rate of change over the past 10 years/3 generations (longer of the two periods)	10-30%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	10-30%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	10-30%	-	-	-
Generation length	5.58 years	-	-	-
Number of subpopulations	8-100	-	-	-
Percentage of mature individuals in largest subpopulation	1-89%	-	-	-

Population justification: The five-yearly census of managed sites in 2021 counted 863 pairs: 491 pairs on the North Island and 372 on the South Island (DOC 2022), equating to approximately 1,700 mature individuals. It is difficult to obtain an accurate global population estimate due to the widespread nature of the rivers and streams that the species inhabits in remote areas of New Zealand, but the wider population is not thought to exceed 2,500 mature individuals and is placed here in the range 1,500-2,499 mature individuals. The largest numbers are found in rivers and streams in the catchments of the Bay of Plenty, the central North Island, Northwest Nelson, the West Coast and Fiordland (Whio Recovery Group, in Glaser et al. 2010), and the largest subpopulation at Tongariro numbers slightly more than 100 pairs (DOC 2022).

Trend justification: There are declines in both distribution and abundance with the result that the species is now restricted to disjunct populations (Whitehead et al. 2008). The overall population is thought to be declining especially on the South Island (Glaser et al. 2010). Survival studies conducted at three security sites; Northern Fiordland (Whitehead et al. 2008), Te Urewera (Glaser and Allerby 2010) and Wangapeka (DOC 2014a) demonstrate potential declines associated with predator impacts and weather events (Simpkins et al. 2015).
Population modelling indicates ongoing decline in the absence of management (Scrimgeour 2015a). Positive population responses have been observed where predator control has taken place, including a 2.8-fold population increase in four years with three fledged young per pair each year and 94% chick survival (Glaser et al. 2010). In contrast, unmanaged sites had a 91% nest failure rate and productivity was 0.64 fledged young per pair per year (Glaser et al. 2010), suggesting that the species is declining in areas without management intervention. The population is suspected to be declining at a rate equivalent to 10-30% in three generations as non-managed sites continue to experience high levels of predation, and this is thought to be ongoing (Robertson et al. 2021).

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
New Zealand	extant	native	yes

Country/Territory	IBA Name

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Temperate	major	resident
Wetlands (inland)	Permanent Rivers/Streams/Creeks (includes waterfalls)	major	resident
Altitude	0 - 1050 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Livestock farming & ranching - Agro-industry grazing, ranching or farming	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Livestock farming & ranching - Small-holder grazing, ranching or farming	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Climate change & severe weather	Storms & flooding	Timing		Scope		Severity		Impact
		Future		Whole (>90%)		Unknown		Unknown
		Stresses Ecosystem degradation
Human intrusions & disturbance	Recreational activities	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species disturbance
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Canis familiaris	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Felis catus	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Mustela erminea	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Mustela furo	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Mustela nivalis	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Named species	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Salmo trutta	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Competition
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Trichosurus vulpecula	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Anguilla dieffenbachii	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Circus approximans	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Falco novaeseelandiae	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Problematic native species/diseases - Gallirallus australis	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Natural system modifications	Dams & water management/use - Dams (size unknown)	Timing		Scope		Severity		Impact
		Past, Likely to Return		Minority (<50%)		No decline		Past Impact
		Stresses Ecosystem degradation, Ecosystem conversion

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Recommended citation
BirdLife International (2024) Species factsheet: Blue Duck Hymenolaimus malacorhynchos. Downloaded from https://datazone.birdlife.org/species/factsheet/blue-duck-hymenolaimus-malacorhynchos on 27/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 27/12/2024.