Reliability of the Mallard Wing Age-Determination Technique for Field Use

Hopper, Richard M.; Funk, Howard D.

doi:10.2307/3799018

Cited by 15 publications

(7 citation statements)

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“…Upon capture, we attached an NZ Department of Conservation metal leg band with a unique number to the left leg of each female. We determined age as second year (SY) or after second year (ASY) primarily by bursa depth (Hanson ), and then by inspecting the greater secondary coverts (Krapu et al ) and 4 distal primary coverts (Carney and Geis , Hopper and Funk , Pearse et al ). We weighed birds with a spring scale (±10 g; Pesola, Schindellegi, Switzerland).…”

Section: Methodsmentioning

confidence: 99%

Duckling survival of mallards in Southland, New Zealand

Garrick¹,

Amundson

Seddon

2017

J Wildl Manag

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The southern portion of New Zealand's South Island is a productive area for mallards (Anas platyrhynchos) despite a notable lack of permanent or semi-permanent wetlands. Most broods are reared in pastures that may or may not be flooded with ephemeral water. In recent years, there has been an increased conversion from continuous to sporadic grazing that has resulted in a functional change in the emergent and upland vegetation available for broods. In 2014, we investigated mallard duckling survival on different pastures relative to a suite of characteristics pertaining to the adult female, clutch, brood, weather, and habitat. We monitored 438 ducklings from 50 radio-marked females to 30 days post-hatch. Duckling survival was unaffected by pasture type but increased with duckling age, the presence of ephemeral water, and with greater distance from the nearest anthropogenic structure. Survival was lower for broods of second year (SY) females than for broods of after-second year (ASY) females, in areas with more dense cover, and when ducklings moved, on average, greater daily distances. Cumulative 30-day duckling survival ranged from 0.11 for ducklings of SY females without ephemeral water present to 0.46 for ducklings of ASY females with ephemeral water present. Therefore, increasing available seasonal water sources may increase duckling survival. Further, narrow, linear patches of dense cover present in our study could support a greater abundance of predators or increase their foraging efficiency. As such, managers could consider increasing patch sizes of dense cover to reduce predator efficiency, and employing predator removal in these areas to improve duckling survival. Ó 2017 The Wildlife Society.

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Section: Methodsmentioning

confidence: 99%

Duckling survival of mallards in Southland, New Zealand

Garrick¹,

Amundson

Seddon

2017

J Wildl Manag

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“…C. Rowher, unpublished data). In a later study to determine persistence of juvenile characteristics on captive live mallards, Hopper and Funk (1970) found that wingbee participants had accuracy rates between 84% and 91%. Their study provided detailed information regarding the progressive loss of juvenile characteristics, yet results from entire live birds may differ from those based on wings alone.…”

Section: Discussionmentioning

confidence: 99%

“…This first evaluation of wing‐aging techniques, however, lacked blind assessment (i.e., participants were aware of the evaluation) and certainty that birds were of known age, because cloacal examination may not provide definitive determination of age (Esler and Grand ; F. C. Rowher, unpublished data). In a later study to determine persistence of juvenile characteristics on captive live mallards, Hopper and Funk () found that wingbee participants had accuracy rates between 84% and 91%. Their study provided detailed information regarding the progressive loss of juvenile characteristics, yet results from entire live birds may differ from those based on wings alone.…”

Section: Discussionmentioning

confidence: 99%

“…Our objectives were primarily to assess accuracy of age assignment based on wing plumage and, secondarily, to determine accuracy of determining species and sex. Earlier evaluations focused on accuracy of the wing plumage method as performed by individual participants (Carney and Geis , Hopper and Funk ). Our evaluations estimated accuracy of protocols within the operational survey procedure by incorporating wings from birds of known species, sex, and age.…”

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confidence: 99%

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Accuracy of aging ducks in the U.S. Fish and Wildlife Service Waterfowl Parts Collection Survey

et al. 2013

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The U.S. Fish and Wildlife Service conducts an annual Waterfowl Parts Collection Survey to estimate composition of harvested waterfowl by species, sex, and age (i.e., juv or ad). The survey relies on interpretation of duck wings by a group of experienced biologists at annual meetings (hereafter, flyway wingbees). Our objectives were to estimate accuracy of age assignment at flyway wingbees and to explore how accuracy rates may influence bias of age composition estimates. We used banded mallards (Anas platyrhynchos; n = 791), wood ducks (Aix sponsa; n = 242), and blue‐winged teal (Anas discors; n = 39) harvested and donated by hunters as our source of birds used in accuracy assessments. We sent wings of donated birds to wingbees after the 2002–2003 and 2003–2004 hunting seasons and compared species, sex, and age determinations made at wingbees with our assessments based on internal and external examination of birds and corresponding banding records. Determinations of species and sex of mallards, wood ducks, and blue‐winged teal were accurate (>99%). Accuracy of aging adult mallards increased with harvest date, whereas accuracy of aging juvenile male wood ducks and juvenile blue‐winged teal decreased with harvest date. Accuracy rates were highest (96% and 95%) for adult and juvenile mallards, moderate for adult and juvenile wood ducks (92% and 92%), and lowest for adult and juvenile blue‐winged teal (84% and 82%). We used these estimates to calculate bias for all possible age compositions (0–100% proportion juv) and determined the range of age compositions estimated with acceptable levels of bias. Comparing these ranges with age compositions estimated from Parts Collection Surveys conducted from 1961 to 2008 revealed that mallard and wood duck age compositions were estimated with insignificant levels of bias in all national surveys. However, 69% of age compositions for blue‐winged teal were estimated with an unacceptable level of bias. The low preliminary accuracy rates of aging blue‐winged teal based on our limited sample suggest a more extensive accuracy assessment study may be considered for interpreting age compositions of this species. Published 2013. This article is a U.S. Government work and is in the public domain in the USA

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“…The GTC feathers of immature male canvasbacks were also replaced by mid-April. Hopper and Funk (1970) reported that immature male mallards (Anas platyrhynchos) retained GTC feathers into early spring beyond the prebasic I molt. In general, however, most waterfowl retain GSC and MSC feathers through the spring period until the prebasic II molt (Palmer 1976).…”

Section: Discussionmentioning

confidence: 98%