Recruitment Models for Mallards in Eastern North America

Sheaffer, Susan E.

doi:10.2307/4089517

Cited by 16 publications

(16 citation statements)

References 11 publications

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“…Yet, there is no consensus about the effects of density‐dependent processes on recruitment rate, which affects population change and sustainable harvest levels of this and other economically important waterfowl species (Trost et al . 1993, Sheaffer 1998, Johnson et al . 2002, Pöysä et al .…”

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Density‐dependent nest predation – an experiment with simulated Mallard nests in contrasting landscapes

Gunnarsson

Elmberg

2007

Ibis

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Breeding success is a key element of animal population dynamics. In many taxa including birds, nest success, or the proportion of laid clutches that actually hatch, is mainly determined by predation. Previous research gives an inconsistent picture of the prevalence of density‐dependent nest predation and one reason for this is the general lack of well‐designed replicated experiments. Using simulated Mallard Anas platyrhynchos nests and a crossover design for 20 lakes in the nemoral and boreal biotic zones, we tested the predictions that nest survival is negatively density‐dependent and that nest predation is higher in agricultural than in forested landscapes. Study day and daily abundance of waterfowl, other waterbirds, as well as avian predators were included as covariates in the analysis. Model fitting in program mark revealed a general negative effect of nest density on nest survival. In addition, nest survival rate was higher at forest lakes than at lakes in agricultural landscapes, irrespective of nest density. The only covariate producing model improvement was study day; older nests had higher survival rates than recently initiated ones. This is the first replicated lake‐level experimental study showing that nest predation is density‐dependent in waterfowl. The pattern was consistent between landscape types, implying that density‐dependent nest predation may affect habitat choice and population dynamics over large parts of the Mallard's range.

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Density‐dependent nest predation – an experiment with simulated Mallard nests in contrasting landscapes

Gunnarsson

Elmberg

2007

Ibis

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“…Fish andWildlife Service 2004). The recognized need for independent management of the eastern population has been tempered by a dearth of pertinent data (Strange et al 1989, Johnson et al 1997, Sheaffer 1998. Information on demographic rates and resource use for eastern populations is necessary for developing effective conservation strategies in this region.…”

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Demographics of Breeding Female Mallards in Southern Ontario, Canada

Hoekman

Gabor

Maher

et al. 2006

Journal of Wildlife Management

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Reliable estimates of breeding‐ground demographic rates are needed to develop effective conservation strategies for mallard (Anas platyrhynchos) breeding habitat in eastern North America. We radiomarked 224 female mallards in an agricultural landscape in southern Ontario, Canada, during 1997–2000. At each of 4 sites, 1 during each year, we estimated survival of adult females, breeding incidence, nesting effort, clutch size, nesting habitat use, nest survival, and hen success. We also examined the influence of nest age, date, and habitat on nest survival and the influence of date and female age on survival of adult females. Almost all females remaining on site were observed to initiate ≥ 1 nest (x̄ = 0.97, range = 0.95–0.98), we detected a mean of 2.07 (1.80–2.36) nests per female each season, and full clutch size averaged 9.56 (9.1–10.0). For most sites, females nested in grassland and hay land more than expected relative to habitat abundance, nested in wetlands and woody habitats in proportion to abundance, and avoided cropland and developed areas. Survival of adult females from 25 March to 15 July averaged 0.75 (0.65–0.84). Estimates from our best model showed relatively uniform survival across the breeding season, with the exception of large decreases for 2 sites during the peak of the onset of hay cutting. Nest survival averaged 0.13 (0.11–0.15). Our best model supported increasing survival with nest age but did not include variation relative to habitat or date, except in hay land. Nest survival in hay land was high relative to other habitats early in the nesting season, but declined sharply with the onset of hay cutting. Hen success averaged 0.37 (0.25–0.46). Because estimated nest survival varied little among sites and habitats and because suitable nesting habitat appeared abundant, we suggest that upland habitat conservation will accrue only limited demographic benefits. Incentives to alter hay‐cutting practices may decrease mortality of nests and nesting females, but we believe such incentives are unlikely to be cost efficient and that experiments would be needed to reliably assess benefits.

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“…Fish andWildlife Service 2004). The recognized need for independent regional management of eastern mallards has been impeded by a lack of pertinent data and knowledge of factors influencing population dynamics (Strange et al 1989, Johnson et al 1997, Sheaffer 1998. We present demographic analyses of eastern mallards with the goals of assessing demographic performance during the breeding season, aiding development of effective management strategies for eastern mallards, and contrasting dynamics of eastern versus midcontinent populations.…”

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Population Dynamics of Mallards Breeding in Agricultural Environments in Eastern Canada

Hoekman

Gabor

Petrie

et al. 2006

Journal of Wildlife Management

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Population dynamics of mallards (Anas platyrhynchos) in eastern North America likely differ relative to the midcontinent population, but independent management has been hampered by lack of data. We used data from radiomarked females from 4 sites in southern Ontario and 1 site in New Brunswick during 1992–2000 to assess demographic performance during the breeding season and to inform regional management strategies. For each site, we estimated recruitment of female young to 30 days posthatch per breeding female and projected the finite rate of population growth Λ, assuming annual survival typical of the region. We constructed a matrix population model for females and conducted perturbation analyses (i.e., analytic sensitivities and elasticities) to predict response of Λ to change in vital rates. Excluding 1 site, we estimated mean recruitment of 0.89 (range= 0.79–0.98). At 1 site, duckling survival approaching zero resulted in extremely low estimated recruitment (0.08). Perturbation analyses indicated that Λ was highly sensitive to changes in nest survival and nonbreeding survival and moderately sensitive to changes in survival of breeding females. Recruitment for most of our sites was >2 times the mean for the Prairie Pothole Region of Canada and likely was sufficient to maintain populations despite relatively high hunting kill in the region. Despite high sensitivity of Λ to nest survival, intensive management to increase nest survival likely would be inefficient because of uniform nest survival among habitats and low nest densities. Because recruitment levels were generally high but densities of breeding pairs low, we recommend protection, enhancement, and restoration of wetlands to maintain and increase habitat suitability for breeding mallards as likely the most cost‐efficient management strategy to benefit populations. Relatively high hunting kill and high sensitivity of Λ to nonbreeding survival imply that harvest is important to regional population dynamics and suggest the potential effectiveness of adaptive harvest management.

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Recruitment Models for Mallards in Eastern North America

Cited by 16 publications

References 11 publications

Density‐dependent nest predation – an experiment with simulated Mallard nests in contrasting landscapes

Density‐dependent nest predation – an experiment with simulated Mallard nests in contrasting landscapes

Demographics of Breeding Female Mallards in Southern Ontario, Canada

Population Dynamics of Mallards Breeding in Agricultural Environments in Eastern Canada

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