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Blue duck

The blue duck (Hymenolaimus malacorhynchos), known as whio in Māori, is a medium-sized perching duck endemic to New Zealand, distinguished by its slate-blue plumage, chestnut-spotted breast, and pale grey bill with black flaps adapted for filtering invertebrates from fast-flowing waters.^[1]^[2] Inhabiting clear, turbulent rivers and streams in forested upland areas, it serves as an indicator of aquatic ecosystem health due to its dependence on unpolluted, oxygenated habitats.^[3] Classified as Endangered by the IUCN with a global population estimated at 1,500–2,500 individuals, the species has undergone severe declines primarily from predation by introduced mammals, especially stoats targeting nesting females.^[4]^[5] Conservation initiatives focusing on predator control have tripled breeding pairs in managed areas over the past decade, highlighting the efficacy of targeted feral mammal eradication in reversing local extinctions.^[6] Unlike typical ducks, whio produce a distinctive whistling call rather than quacks and exhibit strong site fidelity, with pairs defending linear territories along river corridors.^[7] As a taonga species culturally significant to Māori, ongoing threats from habitat alteration and flooding underscore the need for sustained riverine protection to prevent further range contraction.^[3]^[8]

Taxonomy and Nomenclature

Scientific Classification

The blue duck (Hymenolaimus malacorhynchos) is classified in the order Anseriformes and the family Anatidae, which encompasses ducks, geese, and swans. It constitutes the sole species within the monotypic genus Hymenolaimus, reflecting its distinct phylogenetic isolation.^[9]^[10] Phylogenetic analyses, including molecular sequence data from mitochondrial and nuclear genes, position Hymenolaimus as an early-diverging lineage within Anatidae, separate from typical dabbling ducks (Anas spp.) and diving taxa.^[11]^[12] Genetic divergence between North and South Island populations, estimated at approximately 2% in mitochondrial DNA, suggests isolation during the late Pleistocene, with minimal gene flow thereafter.^[13]^[14] Distinctive morphological features, such as the soft, fleshy bill (reflected in the specific epithet malacorhynchos, from Greek for "soft bill"), enable precise gleaning of aquatic invertebrates from rocky substrates in fast-flowing streams, differentiating it from the broader bills of surface-feeding or deep-diving congeners.^[15]^[16] The absence of fossil records for H. malacorhynchos in New Zealand, including offshore islands, underscores its status as a long-isolated endemic with no documented extinct relatives, consistent with divergence predating recent avian radiations on the archipelago.^[4]^[8]

Etymology and Cultural Names

The common English name "blue duck" refers to the species' characteristic slate-gray blue plumage.^[17] The binomial scientific name Hymenolaimus malacorhynchos, established by Johann Friedrich Gmelin in 1789, derives from Greek roots: the genus Hymenolaimus alludes to membranous throat structures associated with its feeding adaptations, while the specific epithet malacorhynchos combines malakos (soft) and rhynchos (bill or snout), describing the bird's uniquely soft, fleshy bill suited to its foraging in swift currents.^[18]^[7] In Māori tradition, the bird is called whio (pronounced "fee-oh"), an onomatopoeic name mimicking the male's high-pitched, disyllabic whistling call "whi-o", which serves territorial and mating functions.^[2]^[3] Whio is regarded as a taonga (treasured possession) by various iwi, embodying cultural and spiritual significance tied to riverine landscapes central to ancestral practices; archaeological middens and early historical accounts document its former abundance across New Zealand prior to European arrival around 1769, with post-contact declines evidenced by reduced sightings in 19th-century records amid habitat loss and introduced predators.^[3]^[19]

Physical Characteristics

Morphology and Plumage

The blue duck (Hymenolaimus malacorhynchos) is a medium-sized duck measuring approximately 53 cm in total length, with adult males slightly larger than females, averaging 1000 g in weight compared to 770–900 g for females.^[8]^[2] Sexual dimorphism is minimal, confined primarily to modest differences in body size and subtle plumage variations, rather than pronounced color distinctions typical in many anatids.^[1] Adult plumage is predominantly slate-blue to blue-grey, providing camouflage against rocky river substrates, with males displaying a chestnut breast band and faint greenish iridescence on the head, neck, and upperparts.^[2] Females exhibit similar coloration but with reduced chestnut extent and iridescence intensity.^[2] Juveniles possess duller, less vibrant feathers and a darker bill, transitioning to adult plumage by around six months of age.^[2]^[20] The bill is notably broad and spatulate, pale grey to pink with a blackish nail at the tip, and equipped with soft, rubbery lateral flaps or "lips" that facilitate scraping and dislodging aquatic invertebrates, such as larvae, from submerged rocks and gravel in fast-flowing, turbulent streams.^[21]^[22] This specialized structure protects the bill from abrasion while enabling precise foraging in high-velocity waters, reflecting adaptations to a niche of rheophilic (current-loving) existence.^[21] Adults undergo an annual wing moult shortly after breeding, rendering them temporarily flightless for several weeks, during which they seek cover in dense vegetation or secluded river sections to minimize predation risk.^[23]^[18] This period of vulnerability underscores the species' dependence on inaccessible habitats for survival.^[23]

Vocalizations and Displays

The blue duck employs a repertoire of high-pitched whistles and growls for contact, territorial defense, and pair maintenance, with acoustic properties enabling transmission over turbulent river noise. Males produce a piercing, rising whistle termed "whio" or "whi-whio," spanning 2-6 kHz, often delivered in the extended-neck posture with erected neck feathers and frequently in dawn or dusk duets.^[24] Females respond with a prolonged rattling growl ("grrr-grrRRrr") below 2 kHz or a sharper "gak-gak-grrak" under 3 kHz during confrontations, typically from a strained upright stance.^[24] These vocalizations, lacking the quacks common in other anatids, leverage higher frequencies to penetrate the low-frequency roar of rapids and forested acoustics, as observed in field studies along New Zealand's Manganui a te ao River.^[24] ^[1] Visual displays complement these calls, particularly in courtship and intruder deterrence, where ritualized postures reinforce territorial claims and mate attraction. Both sexes execute head-bobbing, a forward-scooping pump of the head that males pair with ascending whistles and females alternate side-to-side with growls.^[24] Males initiate courtship via the dip-shake, involving lateral bill dips and shakes toward the female with fanned tertials and rustling feathers, or the head-low rush—a swift over-water charge with tucked wings and scooping head motion, often preceding copulation.^[24] The lateral posture, with head bowed and crest depressed, signals subdued approach during pair bonding.^[24] Such behaviors, more pronounced in males, align with heightened activity during the breeding period from late winter through spring, when pairs defend linear river territories.^[2]

Habitat and Distribution

Preferred Environments

The blue duck (Hymenolaimus malacorhynchos) preferentially occupies fast-flowing, clear rivers and streams with cobble and boulder substrates, which facilitate foraging on aquatic invertebrates by allowing access to benthic habitats.^[3] These environments feature medium to steep gradients, stable flows, and high oxygen levels with minimal sediment, conditions that sustain abundant invertebrate prey through enhanced aeration and reduced smothering of stream beds.^[4]^[25] Riparian zones with unmodified forest cover, including overhead canopy and vegetation reaching the water's edge, are selected over open pastoral areas, as such forests provide thermal regulation, cover from aerial disturbance, and input of terrestrial invertebrates via leaf fall and woody debris.^[3]^[4] The species utilizes an altitudinal gradient from 0 to 1,050 meters, concentrating in upper catchments where hydrological stability and prey density align with these vegetated, confined channels.^[4] Microhabitats critical for nesting and roosting include undercut banks with woody debris, riverbank caves, log jams, and dense understory vegetation, offering flood-resistant shelters proximate to foraging sites.^[3]^[4] Habitat selectivity emphasizes physical stability and channel morphology over broader landscape features, with pairs defending linear territories along these river segments year-round.^[26]

Historical and Current Range

The blue duck (Hymenolaimus malacorhynchos), endemic to New Zealand, historically occupied a wide distribution across forested river systems in both the North and South Islands prior to human arrival. Its pre-human range encompassed high-altitude tarns, lakes, and rivers as well as segments of bush-edged lowland rivers and lakes, reflecting adaptation to diverse fast-flowing freshwater habitats.^[2] Since Polynesian settlement around 1280 CE and subsequent European colonization from 1840, the species' range has contracted substantially, becoming fragmented and largely confined to remote, unmodified catchments with intact forest cover. Current populations are patchily distributed, persisting primarily in areas with suitable clean, oxygenated fast-flowing rivers, while absent from many formerly occupied lowland and modified sites.^[4]^[22] Key strongholds include the central North Island ranges such as Urewera and Ruahine, and the west coast of the South Island, including regions like Kahurangi National Park. Analysis of range contraction attributes a greater proportion—approximately 68%—to mammalian predation impacts across suitable habitats, with habitat modification accounting for the remaining 32%, underscoring that predator pressures have driven losses even in persistent habitat types.^[27]^[25] Recent surveys demonstrate localized persistence, with an ongoing Department of Conservation assessment in Kahurangi National Park, started in 2020, revealing a 340% increase in blue duck numbers relative to 1998–2000 baselines as of 2023, highlighting variability in population trajectories across the fragmented range.^[28]

Behavioral Ecology

Foraging Strategies

The blue duck (Hymenolaimus malacorhynchos) forages primarily through active tactile probing and scraping along stream beds in fast-flowing rivers, targeting sessile benthic invertebrates such as caddisfly (Trichoptera) and midge (Chironomidae) larvae adhering to rocks.^[29] Its specialized bill features soft, rubbery flaps of thickened keratinized epidermis along the upper mandible margins, embedded with sensory Herbst's corpuscles that enhance tactile detection of prey, enabling the bird to scrape larvae from rock surfaces without visual reliance.^[30]^[21] These adaptations contrast sharply with the passive surface-filtering of dabbling ducks, allowing the blue duck to exploit turbulent, substrate-bound microhabitats where prey densities range from 3,741 to 14,417 individuals per square meter on stones.^[29] For mobile prey like mayfly and stonefly nymphs, blue ducks switch to visual cues, employing a narrow, tapering bill for precise pecking or lunging strikes, supported by a frontal binocular visual field of up to 34° that positions the bill within the line of sight.^[30] Gleaning occurs mainly from the tops and undersides of submerged or emergent boulders, with occasional shallow dives or grazing in deeper water to access less accessible items.^[29] Foraging bouts involve siphoning or upending in shallow riffles, prioritizing high-value prey like free-living Hydrobiosidae larvae over lower-ranked cased forms, though selectivity appears opportunistic rather than strictly preferential.^[29] Activity patterns are predominantly diurnal with crepuscular peaks in early morning and late afternoon, extending nocturnally under low-light conditions when water clarity permits visual foraging.^[2] In rivers with invasive brown trout (Salmo trutta), foraging efficiency declines due to competitive depletion of shared invertebrate prey and benthic habitat alterations; experimental channels with trout prompted avoidance by captive blue ducks, correlating with reduced macroinvertebrate abundance and shifts in community composition unfavorable to the ducks' diet.^[31]^[23] Blue ducks form long-term monogamous pair bonds that are maintained throughout the year, with pairs aggressively defending linear territories along fast-flowing streams and rivers.^[2]^[32] These territories typically range from 1 to 5 km in length, averaging about 1.5 km, which supports exclusive access to foraging sites rich in aquatic invertebrates essential for their diet.^[33]^[3] Territorial defense involves vocalizations, chases, and physical confrontations between pairs or intruding individuals, effectively minimizing overlap and ensuring resource security in environments where food availability is constrained by stream flow and substrate conditions.^[34]^[35] Males particularly intensify patrols near nest sites during incubation, while both sexes contribute to year-round vigilance, reflecting adaptations that prioritize stable food access over social affiliation to enhance reproductive output in predator-prone habitats.^[23]^[36] Juveniles disperse after fledging and must secure high-quality territories to survive and pair, with recruitment success linked to the availability of undefended stream sections featuring suitable rapids and pools; poor territory quality correlates with higher juvenile mortality due to inadequate foraging opportunities.^[37] This territorial system results in low population densities, as each pair's exclusion of competitors limits local abundance while optimizing per-pair breeding success through guaranteed resource control.^[33]

Reproduction and Life Cycle

Breeding in blue ducks occurs annually, primarily from mid-August to October, with pairs selecting nest sites near rivers in cavities, caves, under dense vegetation, or shallow scrapes lined with twigs, grass, and down.^[4]^[3] Females lay clutches of 4-9 creamy white eggs at intervals of about two days, with an average clutch size of 5-6 eggs.^[15]^[2] Only the female incubates the eggs for 33-35 days, during which the male guards the vicinity of the nest.^[2]^[32] Upon hatching, precocial ducklings are tended by both parents, who lead them to water for foraging; the young achieve fledging capability after approximately 70 days, at which point parental care diminishes as adults initiate their post-breeding moult.^[38]^[23] Post-fledging, adults undergo an annual wing moult lasting about 2 weeks between December and May, rendering them temporarily flightless and prompting retreat to concealed tributary areas, which imposes significant energetic and vulnerability constraints on reproduction.^[19]^[23] Empirical data from monitored populations indicate an average breeding productivity of 1.3 fledglings per pair per year across 58 observed attempts, reflecting nest success rates around 54% with higher hatching in early-season nests.^[32]^[15] However, subsequent high juvenile mortality—exceeding 60% in unmanaged areas—translates to low effective recruitment, limiting population growth despite potential for multiple breeding seasons.^[3] Blue ducks reach sexual maturity at about 1-2 years and exhibit strong pair fidelity, often maintaining lifelong territories.^[8]^[7] In the wild, average lifespan is 7-8 years, though individuals exceeding 10 years occur; population dynamics are predominantly regulated by juvenile losses rather than adult longevity, underscoring the biological bottlenecks in their life cycle.^[19]^[8]

Threats and Population Dynamics

Introduced Predators and Competition

Introduced predators pose the primary threat to blue duck (Hymenolaimus malacorhynchos, also known as whio) populations, with stoats (Mustela erminea) identified as the leading cause of nest failure and adult mortality. In unmanaged sites, nest failure rates reach 91%, predominantly due to stoat predation on eggs, ducklings, and brooding females, as documented through nest monitoring and camera trap footage.^[4]^[33] Stoats account for up to 50% of nest failures without intervention, dropping to 26% in areas with targeted control, confirming their causal role via direct observations of predation events and autopsy evidence of stoat kills.^[37] Rats (Rattus spp.) primarily target eggs and young ducklings, while ferrets (Mustela furo), feral cats (Felis catus), and dogs prey on adults and juveniles; possums (Trichosurus vulpecula) occasionally disturb nests or consume eggs, exacerbating vulnerability during the breeding season from late winter to early summer.^[23]^[3] These impacts are substantiated by predator sign at nest sites, tracked individuals, and recovery of remains showing bite marks consistent with mammalian predators.^[39] Predation collectively drives over 80% of whio decline, with stoats disproportionately affecting breeding success due to their ability to raid remote riverine nests.^[40] Interspecific competition arises from introduced brown trout (Salmo trutta), which prey on aquatic invertebrates—the core of whio diet—reducing prey availability in shared stream habitats, though this effect is secondary to direct predation.^[23] Native longfin eels (Anguilla dieffenbachii) also consume ducklings and compete for benthic macroinvertebrates, but introduced trout amplify resource depletion through higher densities and aggressive foraging.^[23] No empirical data links climate variation directly to whio declines, with predation remaining the dominant causal factor.^[41] The predatory impact is evidenced by population responses to control efforts, such as in Kahurangi National Park, where whio territories increased from 18 in 2017 to 53 in 2023 following stoat trapping and supplementary measures, demonstrating that suppressing introduced mammals reverses declines.^[28] Critics note that incomplete predator eradication limits long-term gains, yet replicated monitoring across sites affirms control's efficacy in boosting productivity from 0.64 fledged young per pair annually in unmanaged areas to higher rates where predators are reduced.^[4]^[42]

Habitat Alteration and Other Factors

Hydroelectric dam construction and agricultural practices have historically impacted blue duck habitats by altering river flow regimes and increasing sedimentation loads, which degrade the clean, fast-flowing streams essential for foraging and nesting. Dams modify natural water flows, reducing suitable habitat in affected catchments, while upstream farming contributes to sediment accumulation that clogs riffles and reduces invertebrate prey availability.^[4]^[19] These changes contributed to range contraction following European settlement, particularly through riverside development and forest clearance that increased siltation.^[8]^[18] Contemporary evidence indicates that ongoing habitat alteration plays a lesser role in current declines compared to predation pressures, with habitat modification accounting for smaller-scale losses amid otherwise stable high-quality sites in forested upper catchments. Claims of widespread pollution or climate-driven warming effects, such as elevated temperatures reducing oxygen levels, remain speculative and lack direct empirical linkage to verified population trends for this species.^[27]^[25] Disease is rare among blue ducks, with no documented outbreaks significantly affecting populations, though surveillance continues due to potential vulnerabilities in isolated groups. Hybridization with other duck species is absent, as blue ducks maintain strong reproductive isolation in their specialized riverine niches. Stochastic events like severe floods pose natural risks by destroying nests, reshaping river channels, displacing families, and temporarily eliminating food sources, with impacts exacerbated by low population densities that hinder rapid recolonization.^[3]^[40] Pre-European Māori hunting of blue ducks was sustainable and culturally significant, targeting birds primarily during moulting periods without evidence of overexploitation, as populations remained widespread and abundant at the onset of European colonization around 1840. Post-contact declines correlate more closely with introduced factors than with intrinsic habitat fragility or prior indigenous practices.^[43]^[18]

Population Estimates and Trends

The global population of the blue duck (Hymenolaimus malacorhynchos), also known as whio, is estimated at 2,500–3,000 individuals, with no subpopulation exceeding 250 individuals.^[4]^[44] The species is classified as Endangered by the International Union for Conservation of Nature (IUCN) due to ongoing declines driven by fragmentation and small population sizes.^[4] In New Zealand, it holds a Nationally Vulnerable status under the New Zealand Threat Classification System, reflecting persistent risks despite localized monitoring efforts.^[45] Historical trends indicate a marked decline from the early 1900s to 2000, with range contraction and fragmentation reducing the species to isolated river headwater populations primarily in the central North Island and western South Island.^[37] Post-2010 surveys show overall stability or inferred continued decline at the national scale, with breeding pairs estimated at no more than 1,000 as of 2011, though no broad rebound is evident absent targeted management.^[2] Population estimates remain conservative due to survey difficulties in fast-flowing, noisy stream habitats, where the birds' high-pitched whistling calls are often masked by water turbulence, potentially leading to undercounts of dispersed individuals.^[37] Recent findings underscore estimation challenges and hidden resilience, including the 2025 discovery of a previously undocumented group of seven whio in the Paparoa Ranges' Motukiekie Wilderness area, detected via detection dog surveys in terrain historically considered unoccupied.^[46] Such revelations suggest that fragmented, remote populations may contribute more to totals than prior acoustic or visual censuses indicate, though comprehensive national surveys as of 2024–2025 still peg the total below 3,000.^[47]

Conservation Measures

Predator Control Initiatives

The Department of Conservation's (DOC) Whio Forever program, established in 2011 with Genesis Energy, implements intensive stoat trapping grids along river corridors to mitigate predation on whio. By 2023, the program maintained 32,142 traps across 1,631 km of rivers at 10 sites, protecting 694 breeding pairs nationwide.^[48] Large-scale trapping has significantly enhanced nesting success and productivity, with controlled areas yielding more fledglings per pair than untrapped sites, where stoat predation causes up to 90% nest failure annually.^[39] ^[49] Community and hunter involvement bolsters these efforts, as seen in the Sika Foundation's 43 km trapping network in Kaimanawa Forest Park, maintained by volunteers who report heightened whio encounters that inform population monitoring.^[50] Ground-based methods provide targeted control but face challenges from stoat reinvasion in incompletely covered areas, limiting long-term stability without supplementary measures.^[42] Aerial application of 1080 poison, often combined with trapping, demonstrates superior efficacy for whio conservation in extensive forested terrains; DOC monitoring reveals higher duckling production post-1080 than with trapping alone, while cost analyses confirm 1080's greater efficiency over ground methods in most conservation estates.^[51] ^[52] Empirical outcomes, such as a 340% whio increase in Kahurangi National Park following sustained predator operations, validate these approaches against narratives dismissing poison tools, though reinvasion risks persist without sustained coverage.^[53] ^[42]

Captive Breeding and Reintroductions

Captive breeding programs for the whio (blue duck, Hymenolaimus malacorhynchos) are coordinated by the New Zealand Department of Conservation (DOC) in partnership with facilities such as Orana Wildlife Park, Pūkaha National Wildlife Centre, and the Isaac Conservation & Wildlife Trust, focusing on both insurance populations and supplementation of wild stocks through ex-situ propagation.^[54]^[55] These efforts include maintaining breeding pairs in aviaries tailored to whio's territorial needs and implementing the Whio Operation Nest Egg (WHIONE), where eggs are retrieved from wild nests, artificially incubated, and ducklings hand- or parent-reared to the juvenile stage before release.^[56] This head-starting approach bypasses the high predation mortality—often exceeding 90% for wild ducklings from introduced mammals like stoats—by producing larger, more resilient juveniles capable of evading predators and navigating fast-flowing rivers.^[42] Annual output from these programs has included records such as 33 juveniles reared and released by Ducks Unlimited in 2019, with multiple sites contributing dozens more across South and North Island subspecies to maintain genetic diversity and avoid inbreeding in fragmented wild populations.^[57]^[58] Reintroductions target predator-controlled river valleys to maximize establishment success, with juveniles undergoing "fast-water training" simulations prior to translocation to enhance foraging and swimming skills in torrent habitats.^[59] A milestone release occurred on 30 January 2025 in the Moeraki Valley, north of Haast, where seven captive-reared juveniles—sourced from South Island breeding programs—were soft-released into a 50,000-hectare area under intensive stoat and rat control, marking the first supplementation for this site and involving collaboration with Ngāti Māhaki iwi.^[60] Post-release monitoring employs radio telemetry to track dispersal, survival, and breeding integration, revealing that while transmitter weight loss can necessitate removal, released whio often exhibit site fidelity akin to wild individuals, establishing territories along release rivers with minimal evidence of behavioral deficits from captivity.^[61] Such translocations have demonstrated viability in boosting local numbers, though long-term genetic viability requires ongoing admixture with wild stock to counter potential founder effects in small release cohorts.^[18] Despite successes in population augmentation, captive breeding carries risks of maladaptation, including reduced wariness of predators or suboptimal mate selection, potentially lowering lifetime reproductive output compared to wild-hatched peers; however, head-starting mitigates early-life bottlenecks, with DOC data indicating higher juvenile survival in controlled environments than in unmanaged wild nests.^[42] Programs prioritize [South Island](/page/South Island) subspecies since 2017 to address regional declines, emphasizing pedigree management for outbreeding to preserve adaptive traits like robust bills suited to invertebrate extraction in stony riverbeds.^[55] Overall, these interventions have contributed to stabilizing whio demographics, though efficacy hinges on concurrent in-situ predator suppression to prevent post-release attrition.

Monitoring and Recent Developments

A survey in Kahurangi National Park, initiated in 2020 by the Department of Conservation (DOC), recorded 846 adult whio with 335 breeding pairs as of 2023, representing a 340% increase from the 191 adults observed in the 1998-2000 baseline survey, attributed to sustained predator control efforts in the area.^[28]^[53] In July 2025, a previously unknown population of seven whio was detected in the Paparoa Ranges using a trained detection dog, marking the first sighting in that region in decades and highlighting the value of targeted search methods in rugged terrain where traditional surveys are challenging.^[46]^[62] Recent advancements in monitoring include environmental DNA (eDNA) analysis of stream water samples, which has proven effective for non-invasive whio detection in remote habitats, and camera traps deployed along rivers to quantify occupancy and breeding trends, enabling more precise tracking of population responses to interventions.^[63]^[51] DOC's ongoing Whio Forever programme, emphasizing these technologies alongside ground-based surveys, reports localized population stability and growth in managed sites as of 2024-2025, with projections for broader recovery contingent on expanded predator suppression, countering narratives of inevitable decline by demonstrating causal links between control measures and empirical gains.^[64]^[51]

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Whio Journal: Whio Fight Club | Conservation blog
Sep 29, 2020 · Whio are renowned for both their territoriality and loyalty, so the scrapping is about establishing and defending a place to call home, and a mate.Missing: behavior | Show results with:behavior
[35]
The food and feeding apparatus of the Blue Duck Hymenolaimus ...
Aug 9, 2025 · This paper describes a preliminary study of the feeding behaviour of the territorial Blue Duck. The bird is unusual in possessing lateral ...<|control11|><|separator|>
[36]
Whio / blue duck - Project Janszoon
The name whio means whistle in Māori and describes the call of the male bird. They are a taonga (treasured) species to Māori and classified as a nationally ...<|separator|>
[37]
[PDF] Status of blue duck (whio) populations in Fiordland, New Zealand, in ...
population growth rates. Prior to stoat control, the population growth rate for whio in the Arthur was 0.91, indicating a declining population. In ...Missing: contraction | Show results with:contraction
[38]
10 things you may not know about whio - Conservation blog
Mar 24, 2017 · 1. Whio live in fast rivers. Whio/blue duck are one of the most unique ducks out there because they have adapted to live in fast-flowing rivers.
[39]
Large scale predator control improves the productivity of a rare New ...
Whio, Hymenolaimus malacorhynchos, are a threatened New Zealand waterfowl that has been declining in both distribution and abundance. We conducted a six-year ...Missing: contraction percentage
[40]
Whio – threats and conservation - Science Learning Hub
Aug 6, 2017 · Whio are a protected species and are classified as endangered by the IUCN and are listed as nationally vulnerable in the New Zealand Threat Classification ...Missing: contraction percentage
[41]
(PDF) Effects of predation by introduced mammals and mortality due ...
Aug 6, 2025 · The extinction risk to the endangered blue duck (Hymenolaimus malacorhynchos) increased by 69% due partially to the impact of floods (Simpkins ...Missing: seasonal shifts
[42]
Combined control contains the key to whio population growth
Mar 31, 2022 · The findings show that 1080 used alongside trapping can keep introduced predators at bay – giving whio populations a chance to grow. The study ...Missing: evidence | Show results with:evidence
[43]
Whio – blue ducks | Te Ara Encyclopedia of New Zealand
Mar 1, 2009 · ... Māori name, which means whistle. The female has a grating alarm call. Activity. Whio often stay under cover in daylight, feeding at dawn and ...
[44]
Blue ducks - how different is 'different'? - Predator Free NZ Trust
Aug 3, 2017 · Blue ducks (whio) live in both the North and South Island – they're isolated by distance, but how isolated are they genetically?
[45]
Whio/blue duck recovery plan 2009-2019: DOC's work
The whio/blue duck (Hymenolaimus malacorhynchos) is an endangered species that is listed as Nationally Vulnerable under the New Zealand Threat Classification ...
[46]
New Whio duck population discovered in Paparoa Ranges | West ...
Jul 8, 2025 · The team celebrated the sighting of a previously unknown population of seven Whio/Blue Duck within the Motukiekie Wilderness Trust project area.
[47]
[PDF] Annual Report July 2023 – June 2024 - Genesis Energy
With an estimated total population of 3,000, the species faces a very real risk of becoming extinct. Whio. Photo: Sabine Bernert. Page 3. Photos clockwise from ...
[48]
[PDF] Whio Forever annual report July 2022 - June 2023
The partnership involves managing and maintaining traps along 709 km of streams across ten sites. This crucial work is carried out by DOC rangers, private and.
[49]
Stoat attacks female duck and removes eggs - YouTube
Feb 27, 2011 · Each year, female whio (blue duck) find a suitable site to nest. In locations where there is no predator control work up to 90% of these ...
[50]
Whio Awareness Month | - Sika Foundation
Working hard to protect Whio within the Kaimanawa Forest Park, this large-scale trapping network, now 43km, is carried out by approx. 250 Sika Foundation ...
[51]
Blue duck/whio monitoring: National Predator Control Programme
DOC did further research to see if 1080 treatment protected nesting whio over a second breeding season. We monitored at the Wangapeka-Fyfe and Oparara-Ugly ...
[52]
[PDF] Evaluating the use of 1080:
is more cost-effective than ground methods in the majority of the conservation estate. As a pest control method targeting possums, rats and stoats, 1080 is ...
[53]
Big increase in whio numbers in Kahurangi National Park
The current survey, started in 2020 and still underway, has found to date a 340% increase in whio/blue duck numbers in Kahurangi since a DOC ...
[54]
Finding whio - Department of Conservation
Situated near Christchurch, Orana Park has a successful breeding programme for the Whio which has seen many ducks raised in captivity and released back into the ...
[55]
Whio/Blue Duck - Isaac Conservation & Wildlife Trust
The blue duck/whio is found on clean, fast-flowing mountain rivers on both the North and South Islands. They are well adapted to this environment.
[56]
Whio Journal: Anne Richardson – A bird-breeding pioneer
Mar 16, 2021 · Aviaries customised for whio have meant that ICWT have become the backbone of the whio breeding programme in the South Island.
[57]
Positive Whio captive results - Ducks unlimited NZ
Jan 20, 2019 · What a great year we have had with 33 ducklings reared and released over the last two weeks in March. This is a new record.
[58]
DOC - Whio Forever Programme - Zoo and Aquarium Association
Effective trapping of stoats and other introduced predators is the best method to ensure whio survive and thrive. Prior to human settlement and the introduction ...
[59]
Captive Breeding - Pūkaha National Wildlife Centre
Whio / Blue Duck There is one active breeding pair. These birds are hand- and parent-raised at Pūkaha before being sent for 'fast water training' at Tongariro ...
[60]
Whio released for first time in Moeraki valley
Jan 31, 2025 · Date: 31 January 2025. The young birds were released on January 30 by representatives of Ngāti Māhaki and DOC rangers. Whio are a unique ...Missing: Paparoa | Show results with:Paparoa
[61]
Whio survivors still encountered with weight loss - Facebook
Dec 23, 2018 · [Whio] “Survivors from last year's release are still encountered, but the birds had transmitters removed because of weight loss problems ...
[62]
On The Up: New West Coast whio (blue duck) population found by ...
Jul 10, 2025 · Fewer than 3000 whio are left, making them a threatened species. “Like a lot of New Zealand, we have had predators which have greatly ...Missing: threats | Show results with:threats
[63]
(PDF) Finding whio: detection of blue duck using environmental DNA
Aug 10, 2025 · The current capacity of environmental DNA (eDNA) to provide accurate insights into the biodiversity of megadiverse regions (e.g., the ...Missing: camera traps
[64]
[PDF] Annual Report July 2024 – June 2025 - Genesis Energy
Oct 5, 2025 · Whio are one of only four duck species that live all year round on clean, fast-flowing streams and rivers. They are an indicator species, which.