Survival Estimates, Mortality Patterns, and Population Growth of Fennoscandian Mallards<i>Anas platyrhynchos</i>

Gunnarsson, Gunnar; Elmberg, Johan; Dessborn, Lisa; Jonzén, Niclas; Pöysä, Hannu; Valkama, Jari

doi:10.5735/086.045.0603

Cited by 22 publications

(32 citation statements)

References 39 publications

(41 reference statements)

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“…1). Similar figures have also been reported for Mallards marked in Finland (Gunnarsson et al. 2008).…”

Section: Discussionsupporting

confidence: 88%

“…Some of the best supported models included sex and age factors, but from the effect sizes and their variation, these effects were minor. Although Gunnarsson et al. (2008) match our findings, others have detected sex effects in Mallard survival.…”

Section: Discussionsupporting

confidence: 87%

“…1992), older birds perhaps being more experienced in avoiding threats. However, there seems to be no general pattern, as other studies report similar survival estimates for different age classes (Gunnarsson et al. 2008), and discrepancies between studies are possibly due to site‐specific impacts from, for example, hunting pressure, predation and environmental factors.…”

Section: Discussionmentioning

confidence: 88%

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Direct and indirect effects of winter harshness on the survival of Mallards Anas platyrhynchos in northwest Europe

Gunnarsson

Waldenström

Fransson

2012

Ibis

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To understand population dynamics it is necessary to understand vital rates, which may be affected by a wide range of factors including environmental variables such as weather. Weather conditions can affect birds’ vital rates directly through increased mortality due to impaired conditions, or indirectly via changes in body condition and/or behaviour. Most understanding of direct and indirect effects of weather comes from studies of breeding birds, whereas the situation in non‐breeding periods is less clear. Here, we analysed annual survival of non‐breeding Mallard Anas platyrhynchos, the most hunted waterfowl species in Europe, and assessed whether survival is related directly to winter harshness and/or indirectly via changes in winter recovery distributions. Recovery data on Mallards, initially marked in southeast Sweden, were analysed with an information‐theoretic approach using program mark. Over 10 000 Mallards were marked in two time periods, 1964–1982 and 2002–2008, of which 13.3 and 4.7%, respectively, were later recovered. Mallards had lower annual survival in the early trapping period (0.58–0.63) than in the later period (0.69–0.71), with no clear effects of sex, age or year. Within each study period, winter harshness did not directly correlate with survival. However, milder winters may have contributed indirectly to higher survival in the second period, as winter harshness data were correlated with the distances to recovery positions for females, and also because winter recovery areas have shifted northeast during the past decades, possibly indicating a shortened migratory distance. Migration is costly, and there is therefore a likely linkage between migration behaviour and survival of dabbling ducks, in which direct as well as indirect effects of winter harshness may play a role. Other factors, such as hunting pressure, are also likely to have changed in the past decades, and may also have contributed to improved survival of Mallards in northwest Europe.

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“…1). Similar figures have also been reported for Mallards marked in Finland (Gunnarsson et al. 2008).…”

Section: Discussionsupporting

confidence: 88%

Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 88%

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Direct and indirect effects of winter harshness on the survival of Mallards Anas platyrhynchos in northwest Europe

Gunnarsson

Waldenström

Fransson

2012

Ibis

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“…Models fitting best with our data suggest that survival of released Mallards during their first year in the wild was less than 0.04. This rate is much lower than annual estimates based on recovery rates for wild Fennoscandian Mallards ringed as pulli (0.21-0.42, Gunnarsson et al 2008), despite the fact that our study concerns birds ringed at a much older stage (7 weeks of age).…”

Section: Discussionmentioning

confidence: 52%

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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“…data), Fennoscandinavia (21–42%; Gunnarsson et al . ) or North America (66% for immature females; Giudice ). Finally, our estimate did not include the breeding period, which is known to be associated with high mortality rates through predation of females on the nest (Arnold et al .…”

Section: Discussionmentioning

confidence: 99%

Robust estimation of survival and contribution of captive‐bred Mallards Anas platyrhynchos to a wild population in a large‐scale release programme

Guillemain

Legagneux

Souchay

et al. 2016

Ibis

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The survival of captive‐bred individuals from release into the wild to their first breeding season is crucial to assess the success of reintroduction or translocation programmes, and to assess their potential impact of wild populations. However, assessing the survival of captive‐bred individuals following their release is often complicated by immediate dispersal once in the wild. Here, we apply Lindberg's robust design model, a method that incorporates emigration from the study site, to obtain true estimates of survival of captive‐bred Mallards Anas platyrhynchos, a common duck species released on a large scale in Europe since the 1970s. Overall survival rate from release in July until the onset of the next breeding season in April was low (0.18 ± 0.07 se) and equivalent to half the first‐year survival of local wild Mallards. Higher overall detectability and temporary emigration during the hunting period revealed movements in response to hunting pressure. Such low survival of released Mallards during their first year may help prevent large‐scale genetic mixing with the wild population. Nevertheless, by combining our results with regional waterfowl counts, we estimated that a minimum of 34% of the Mallards in the region were of captive origin at the onset of the breeding season. Although most released birds quickly die, restocking for hunting may be of sufficient magnitude to affect the wild population through genetic homogenization or loss of local adaptation. Robust design protocols allow for the estimation of true survival estimates by controlling for permanent and temporary emigration and may require only a moderate increase in fieldwork effort.

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Survival Estimates, Mortality Patterns, and Population Growth of Fennoscandian MallardsAnas platyrhynchos

Cited by 22 publications

References 39 publications

Direct and indirect effects of winter harshness on the survival of Mallards Anas platyrhynchos in northwest Europe

Direct and indirect effects of winter harshness on the survival of Mallards Anas platyrhynchos in northwest Europe

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

Robust estimation of survival and contribution of captive‐bred Mallards Anas platyrhynchos to a wild population in a large‐scale release programme

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