Discrimination of Mallard Strains on the Basis of Morphology

Byers, Steven M.; Cary, John R.

doi:10.2307/3809502

Cited by 14 publications

(16 citation statements)

References 6 publications

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“…Similar morphometric analyses on Canada Goose subspecies (Johnson et al 1979, Moser andRolley 1990) and Mallard (Anas platyrhynchos) strains (Byers and Carey 1991) were successful in discriminating populations when limited to five measurements or less. These analyses showed that taking basic measurements consistently among populations was more important than acquiring numerous additional measurements.…”

Section: Discussionmentioning

confidence: 93%

Morphological Differences in Pacific Coast Populations of Greater White-Fronted Geese

et al. 1995

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Section: Discussionmentioning

confidence: 93%

Morphological Differences in Pacific Coast Populations of Greater White-Fronted Geese

et al. 1995

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“…Only a few game-farm mallards were seen in 1976, and could be distinguished from wild mallards by plumage aberrations and bill and body shape (Byers & Cary, 1991; and many years of pers. obs.…”

Section: Methodsmentioning

confidence: 99%

Pairing in mallards and American black ducks: a new view on population decline in American black ducks

Morton

1998

Animal Conservation

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Data on mating systems suggest that mate choice and dominance advantages by mallard (Anas platyrhynchos) males are not sufficient to explain declines in American black ducks (Anas rubripes). Courtship and pairing of mallards and American black ducks overwintering at a site on the Chesapeake Bay were studied from 1976-1993, during October-March. Mallards declined relative to American black ducks during this period at the study site. Courtship groups and pairs (one exception) consisted of conspecific individuals. Mallards and American black ducks segregated when courting but not when resting. Hybrid males joined courting groups of either species but did not pair successfully with either parental species. Handraised American black ducks hatched from eggs, imprinted on humans, and fledged at the study site, paired with American black ducks even though they were initially the rarer species. Handraised American black ducks avoided pairing with siblings. American black ducks and mallards pair assortatively and hybrids are selected against on the Chesapeake Bay. American black ducks may be declining due to human disturbance rather than due to direct interactions with mallards. Mallards may be increasing because they tolerate human disturbance and through direct release by humans into the American black duck's breeding range.

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“…No known morphological criteria allow distinguishing released from wild Mallards with 100% certainty (pers. obs., Byers and Cary 1991). Released or wild, this study is based on first calendar year birds only, following age determination criteria in Krapu et al (1979).…”

Section: Release Experiments In Hunting Estatesmentioning

confidence: 99%

Low survival after release into the wild: assessing “the burden of captivity” on Mallard physiology and behaviour

Guillemain

Elmberg

et al. 2011

Eur J Wildl Res

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Captive-reared animals used in reinforcement programs are generally less likely to survive than wild conspecifics. Digestion efficiency and naive behaviour are two likely reasons for this pattern. The Mallard is a species with high adaptability to its environment and in which massive reinforcement programs are carried out. We studied physiological and behavioural factors potentially affecting body condition and survival of captive-reared Mallards after being released. Digestive system morphology and an index of body condition were compared among three groups: captive-reared birds remaining in a farm (control), captive-reared birds released into the wild as juveniles (released) and wild-born birds (wild). We also compared behaviour and diet of released vs. wild Mallards. Finally, we conducted a 1-year survival analysis of captive-reared birds after release in a hunting-free area. Gizzard weight was lower in control Mallards, but the size of other organs did not differ between controls and wild birds. The difference in gizzard weight between released and wild birds disappeared after some time in the wild. Diet analyses suggest that released Mallards show a greater preference than wild for anthropogenic food (waste grain, bait). Despite similar time-budgets, released Mallards never attained the body condition of wild birds. As a consequence, survival probability in released Mallards was low, especially when food provisioning was stopped and during harsh winter periods. We argue that the low survival of released Mallards likely has a physiological rather than a behavioural (foraging) origin. In any case, extremely few released birds live long enough to potentially enter the breeding population, even without hunting. In the context of massive releases presently carried out for hunting purposes, our study indicates a low likelihood for genetic introgression by captive-reared birds into the wild population.

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Discrimination of Mallard Strains on the Basis of Morphology

Cited by 14 publications

References 6 publications

Morphological Differences in Pacific Coast Populations of Greater White-Fronted Geese

Morphological Differences in Pacific Coast Populations of Greater White-Fronted Geese

Pairing in mallards and American black ducks: a new view on population decline in American black ducks

Low survival after release into the wild: assessing “the burden of captivity” on Mallard physiology and behaviour

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