Assessing Allowable Take of Migratory Birds

Runge, Michael C.; Sauer, John R.; Avery, Michael L.; Blackwell, Bradley F.; Koneff, Mark D.

doi:10.2193/2008-090

Cited by 62 publications

(148 citation statements)

References 33 publications

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“…The PTL framework is based on the theory of density-regulated population growth [8, 21, 22]. Prescribed Take Level is a generalization of the Potential Biological Removal (PBR) framework [23] and is applicable to a broad range of take applications, including hunting.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of harvest and information needs for North American sea ducks

et al. 2017

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Wildlife managers routinely seek to establish sustainable limits of sport harvest or other regulated forms of take while confronted with considerable uncertainty. A growing body of ecological research focuses on methods to describe and account for uncertainty in management decision-making and to prioritize research and monitoring investments to reduce the most influential uncertainties. We used simulation methods incorporating measures of demographic uncertainty to evaluate risk of overharvest and prioritize information needs for North American sea ducks (Tribe Mergini). Sea ducks are popular game birds in North America, yet they are poorly monitored and their population dynamics are poorly understood relative to other North American waterfowl. There have been few attempts to assess the sustainability of harvest of North American sea ducks, and no formal harvest strategy exists in the U.S. or Canada to guide management. The popularity of sea duck hunting, extended hunting opportunity for some populations (i.e., special seasons and/or bag limits), and population declines have led to concern about potential overharvest. We used Monte Carlo simulation to contrast estimates of allowable harvest and observed harvest and assess risk of overharvest for 7 populations of North American sea ducks: the American subspecies of common eider (Somateria mollissima dresseri), eastern and western populations of black scoter (Melanitta americana) and surf scoter (M. perspicillata), and continental populations of white-winged scoter (M. fusca) and long-tailed duck (Clangula hyemalis). We combined information from empirical studies and the opinions of experts through formal elicitation to create probability distributions reflecting uncertainty in the individual demographic parameters used in this assessment. Estimates of maximum growth (rmax), and therefore of allowable harvest, were highly uncertain for all populations. Long-tailed duck and American common eider appeared to be at high risk of overharvest (i.e., observed harvest < allowable harvest in 5–7% and 19–26% of simulations, respectively depending on the functional form of density dependence), whereas the other populations appeared to be at moderate risk to low risk (observed harvest < allowable harvest in 22–68% of simulations, again conditional on the form of density dependence). We also evaluated the sensitivity of the difference between allowable and observed harvest estimates to uncertainty in individual demographic parameters to prioritize information needs. We found that uncertainty in overall fecundity had more influence on comparisons of allowable and observed harvest than adult survival or observed harvest for all species except long-tailed duck. Although adult survival was characterized by less uncertainty than individual components of fecundity, it was identified as a high priority information need given the sensitivity of growth rate and allowable harvest to this parameter. Uncertainty about population size was influential in the comparison of observed and allowa...

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Section: Methodsmentioning

confidence: 99%

Evaluation of harvest and information needs for North American sea ducks

et al. 2017

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“…Focusing on a temporal pattern, the modeled pattern of variation in this index is referred to as the population trajectory. In combination with population size surveys, BBS trajectories can be used to predict population sizes from areas of overlap and areas covered only by BBS data (Runge et al 2009, Millsap et al 2013, Zimmerman et al 2015.…”

Section: Introductionmentioning

confidence: 99%

Using the North American Breeding Bird Survey to assess broad-scale response of the continent's most imperiled avian community, grassland birds, to weather variability

et al. 2016

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“…This framework extends the formula for allowable take in Runge et al . (), as follows:

H^{normalfemale} false(t false) = F_{normalO} \times {\overset{r}{true}}_{normalMNPL} false(t false) \times 0.5 \cdot . 55 \times \overset{false~}{N} false(t false), and

H^{normalmale} (t) = H^{normalfemale} (t) \times S R

where H female is the number of females that can be removed annually; F O is a factor that directly adjusts the harvest rate to reflect management objectives and the risk tolerance of managers with respect to harvest;

{\overset{false~}{r}}_{MNPL}

is an estimate of the per capita population growth rate from population studies, referenced to population density at MNPL and selected from its sampling distribution to reflect risk tolerance; 0·5 is a factor to calculate female removals assuming an equal sex ratio in the population;

\overset{N}{true}

is an estimate of population size ( N ) from population studies, selected from its sampling distribution to reflect risk tolerance; H male is the number of males that can be removed annually; and SR is a factor that specifies the male‐to‐female ratio in removals.…”

Section: Methodsmentioning

confidence: 99%

Harvesting wildlife affected by climate change: a modelling and management approach for polar bears

Regehr

Wilson

Rode

et al. 2017

Journal of Applied Ecology

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Summary The conservation of many wildlife species requires understanding the demographic effects of climate change, including interactions between climate change and harvest, which can provide cultural, nutritional or economic value to humans.We present a demographic model that is based on the polar bear Ursus maritimus life cycle and includes density‐dependent relationships linking vital rates to environmental carrying capacity (K). Using this model, we develop a state‐dependent management framework to calculate a harvest level that (i) maintains a population above its maximum net productivity level (MNPL; the population size that produces the greatest net increment in abundance) relative to a changing K, and (ii) has a limited negative effect on population persistence.Our density‐dependent relationships suggest that MNPL for polar bears occurs at approximately 0·69 (95% CI = 0·63–0·74) of K. Population growth rate at MNPL was approximately 0·82 (95% CI = 0·79–0·84) of the maximum intrinsic growth rate, suggesting relatively strong compensation for human‐caused mortality.Our findings indicate that it is possible to minimize the demographic risks of harvest under climate change, including the risk that harvest will accelerate population declines driven by loss of the polar bear's sea‐ice habitat. This requires that (i) the harvest rate – which could be 0 in some situations – accounts for a population's intrinsic growth rate, (ii) the harvest rate accounts for the quality of population data (e.g. lower harvest when uncertainty is large), and (iii) the harvest level is obtained by multiplying the harvest rate by an updated estimate of population size. Environmental variability, the sex and age of removed animals and risk tolerance can also affect the harvest rate. Synthesis and applications. We present a coupled modelling and management approach for wildlife that accounts for climate change and can be used to balance trade‐offs among multiple conservation goals. In our example application to polar bears experiencing sea‐ice loss, the goals are to maintain population viability while providing continued opportunities for subsistence harvest. Our approach may be relevant to other species for which near‐term management is focused on human factors that directly influence population dynamics within the broader context of climate‐induced habitat degradation.

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Assessing Allowable Take of Migratory Birds

Cited by 62 publications

References 33 publications

Evaluation of harvest and information needs for North American sea ducks

Evaluation of harvest and information needs for North American sea ducks

Using the North American Breeding Bird Survey to assess broad-scale response of the continent's most imperiled avian community, grassland birds, to weather variability

Harvesting wildlife affected by climate change: a modelling and management approach for polar bears

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