Merging Practice & Life-history Theory for Gamebird Populations: Applied and Basic Solutions to Complex Management Problems (hosted by TWS)

Symposium
ROOM: RSCC, D6
SESSION NUMBER: 8241
 
Population management of North American gamebirds is a critically important component of Wildlife Management, where previous (e.g.. October 1963) and recent (e.g. February 2018) special sections of the Journal of Wildlife Management have both celebrated conservation successes, and highlighted continuing concerns. North American gamebird populations experience wildly divergent population trajectories, where some formerly threatened populations now pose an ‘embarrassment of riches,’ and other formerly abundant populations have declined precipitously. Often these trajectories are not thought to be linked with harvest, but nevertheless, that is where many population management actions occur. Recent declines in, and concerns regarding, sage-grouse and prairie-chicken populations mirror concerns faced by waterfowl managers in the late 1980s, where habitat and climate appear to limit population trajectories, and may have major implications for allowable land use, as well as direct resource consumers. As human populations continue to increase, managers will face enhanced challenges to identify and manage populations of conservation concern. Thus, the purpose of this symposium will be three-fold. First, we wish to discuss pertinent issues facing gamebird populations in North America, in the context of existing challenges, and previous successes. Second, we hope to examine the potential for shared learning across species and guilds and in doing so highlight existing efforts to address complex management issues. Finally, we wish to discuss the potential for the integration of life-history theory and management practices to provide more effective conservation solutions for existing challenges.

1:10PM Applying Life-History Theory to the Conservation & Management of Gamebirds: What We Know and What We Need to Know
  David Koons
Anseriformes and Galliformes are among the best studied and most extensively monitored species in the world. Given their global importance for sport and subsistence hunting, viewing, and ecosystem functioning, great effort has been devoted since the middle part of the 20th century to understanding both the environmental and demographic mechanisms that influence gamebird population dynamics. Here I will discuss the utility of life-history theory as a basis for summarizing our understanding of gamebird population dynamics across species and what remains to be learned. Emphasis will be placed on going beyond just the demographic drivers of population dynamics, and why it is essential to identify functional relationships between environmental drivers and vital-rate responses. I will close by highlighting research needs for sustainably managing gamebird populations in the 21st century.
1:30PM 3. How Habitat and Nutrition Affect Fitness and Population Dynamics.
  Ray T. Alisauskas
Survival and reproduction by free-ranging wildlife can be governed by ambient environmental conditions and habitat variability which, in turn, can influence proper nutrition and energy gain at the population level. Continental-scale shifts from natural habitats to agriculture and temporal changes to climate patterns, particularly in the arctic, have changed how nutrition influences demography of numerous wildlife populations. I describe two long-term studies of arctic-nesting waterfowl that illustrate how vital rates can change over time, in response to large-scale changes in quantity and quality of relevant habitat. Midcontinent lesser snow geese have shown historical increases in abundance leading to concern about the effects of their high-density grazing impacts on arctic ecosystems and sympatric wildlife. I address how variation in the mix of anthropogenic and natural nutrition of midcontinent snow geese has influenced both their survival and reproduction, and possibly their patterns of movement among segments of the breeding metapopulation. Recent decadal patterns in population dynamics were an outcome of changes in both survival and recruitment with density-dependent effects on each. A second long-term mark-recapture study of king eiders decomposes population growth into components of annual recruitment and survival. I address the ecological covariates responsible for driving variation in each fitness component, with consequences for population growth locally and range-wide. Both examples illustrate the importance of long-term studies for detecting large-scale change, and for providing context to current observations and inferences about drivers of wildlife populations and about population health.
1:50PM A Life History Perspective on Harvest Management of Upland Game Birds in a Changing World
  Erik Blomberg
Harvest management of North American game birds has followed two fundamentally different trajectories. For migratory species such as waterfowl, federal protections arising from the migratory bird treaties of the early 20th century catalyzed development of the adaptive harvest management systems used today. These approaches are data-driven, regionalized to biological populations within migratory flyways, and provide feedback mechanisms that allow regulation to change in response to observed population dynamics. In contrast, non-migratory birds, such as grouse, wild turkeys, and quail, are managed by individual state or provincial wildlife agencies. Absent a central coordinating body, approaches to harvest management among agencies are variable, and often lack the same well-developed framework present for waterfowl. Here, I review contemporary harvest management of non-migratory game birds by across all U.S. states, and evaluate whether consistent approaches to harvest management have occurred among species despite lack of formal coordination. I use a life history perspective to ask whether harvest prescriptions (bag limits and season length) are consistently associated with species’ position on along a life history gradient, as indexed by inter-specific variation in traits such as clutch size, body mass, and total reproductive investment. As expected, species that are more fecund, smaller bodied, and shorter lived are more liberally-managed (longer seasons, greater bag limits), compared with those that are longer lived and less fecund, which are more conservatively managed. However, there are also outlier species that have, at least in recent years, been managed both more and less conservatively than warranted by their life histories. I conclude that harvest management of non-migratory game birds has settled on a collective norm that is largely consistent with life history gradients. Nevertheless there is much room for improvement, which may be particularly important in cases where better data can facilitate management decisions in light of ongoing population declines.
2:10PM 5. Thinking Cross-Seasonally: Addressing Density-Dependence within and Among Seasons to Manage Waterfowl Harvest Management.
  Todd Arnold
Density-dependent (DD) feedback on annual survival and fecundity are fundamental components of harvest management models for North American waterfowl, but the DD processes themselves have proven difficult to study. Although absence of correlation between survival and harvest rates is consistent with DD, other hypotheses predict similar patterns. For wildlife populations inhabiting seasonal environments, it may be more instructive to formulate models recognizing seasonal carrying capacity, with pre-breeding populations typically well below breeding-season carrying capacity and post-breeding populations often at or above winter carrying capacity. I illustrate these concepts using an integrated population model (IPM) for American black ducks (Anas rubripes) based on harvest and band-recovery data. Black ducks were banded during late summer (Aug-Sep) and late winter (Jan-Feb), which allowed me to estimate sex- and stage-specific population sizes and survival rates during each time period using harvest-based Lincoln estimators and two-season Brownie models, respectively. Adult survival during the winter period was high and mortality was comprised almost entirely of hunting, but winter survival of adults was uncorrelated with harvest rate or population size. By contrast, fledged juveniles had much lower survival during winter and survival was negatively correlated with harvest rate (juvenile males) and population density (both sexes). Adults had lower survival during the breeding season, and breeding season survival of adult females was negatively correlated with breeding population density. Annual population growth was most strongly correlated with adult female survival during the breeding season, with overwinter survival of juvenile females playing a secondary role. Breeding population size is a poor correlate for assessing DD in waterfowl harvest, but Lincoln estimates derived from pre-season banding and harvest data provide a more appropriate metric for DD processes operating during the winter hunting season.
2:30PM Rethinking harvest management from a life-history perspective
  Benjamin Sedinger, Thomas Riecke, James Sedinger, Frank Rohwer, Cliff Feldheim, Perry Williams
Life-history theory predicts that populations of highly fecund species experiencing moderate to low adult survival, like most dabbling ducks (e.g. ‘fast-paced’), should be more sensitive to factors affecting reproduction, than those affecting survival, while populations of less fecund species that experience high adult survival, like most geese (e.g. ‘slow-paced’), should be more sensitive to factors affecting adult survival, than reproduction. In this way, life-history theory might help to inform efficient management of waterfowl populations in North America. Here we examine how the amount of harvest and drought severity during the breeding season influence the population growth rate of three mallard populations and one wood duck population in North America. Climatic conditions influencing water availability were strongly positively related to population growth rates of wood ducks, western mallards, and midcontinent mallards in our study and was weakly positively related to the population growth rate in eastern mallards. In contrast, harvest regulations and harvest rates did not affect population growth rates in wood ducks and western mallard populations, and was strongly positively related to the population growth rate in midcontinent and eastern mallards. We suggest efforts to conserve fast paced waterfowl, like most duck species, should focus on the effects of habitat loss in breeding areas and climate change, which will be critically important as biologists attempt to understand how to quantify and mitigate direct anthropogenic impacts in a changing world.
2:50PM Refreshment Break
3:20PM 6. the Intersection of Behavioral Ecology and Management: Novel Approaches to the Management of Waterfowl Populations.
  John Eadie
Waterfowl (Anseriformes) offer unparalleled opportunities to test hypotheses in evolutionary and behavioral ecology. This monophyletic clade exhibits remarkable diversity in morphology, life histories, mating systems, parental care, foraging ecology, and spacing/territorially to name a few, and so would seem an ideal group with which to undertake comparative analyses. Yet, with some notable exceptions, this potential has been greatly underutilized. Rather, decades of research on waterfowl have focused primarily on population ecology and management, with good reason – as a highly prized group of gamebirds of national economic importance, there has been a strong and successful effort to manage populations of North American ducks, geese and swans sustainably. I argue that these two approaches – conceptual/theoretical and management/applied – are highly compatible and moreover, in bridging this gap, we not only enhance our understanding of the evolutionary underpinnings of waterfowl behavior and ecology, but we also enable novel approaches to the management of waterfowl populations. In this talk, I first consider why this linkage has faltered and offer suggestions on how we might close the gap. I then briefly review select examples that illustrate the potential value of integrating behavioral ecology and management for both theoretical and applied ecologists. I close by considering some areas where further integration may prove fruitful.
3:40PM Basic Science in the Conservation of Sage-Grouse: How Understanding Lekking Behavior Informs Management
  Gail Patricelli, Alan Krakauer, Jessica Blickley, Eric Tymstra, Ryane Logsdon, Anna Perry, Marcella Fremgen, Chelsea Merriman, Jennifer Forbey
The courtship displays and lek-breeding system of the greater sage-grouse have been studied intensively since the 1970’s. Much of this research uses sage-grouse as a model system to understand the evolution of mating systems and sexually selected traits among diverse vertebrate and invertebrate taxa. With sage-grouse populations in decline, such basic science without an immediate connection to conservation applications may seem like a luxury. However, basic research can directly benefit conservation by helping to engage the public and by informing management planning for sage-grouse and other threatened species. I will discuss examples of the latter—how basic research on courtship and mating behavior is relevant for identifying and mitigating impacts on sage-grouse. Examples include how studies of courtship vocalizations help us to understand the impact of anthropogenic noise on courtship behaviors, and how studies of foraging patterns help and courtship dynamics us to understand how changes in the sagebrush landscape impact reproductive activity. As the need for effective conservation actions becomes more acute, there is more need than ever for communication and collaboration between researchers focused on basic and applied questions.
4:00PM Development of an American Alligator Adaptive Harvest Management Framework: What Can be Learned from Waterfowl Management?
  Abigail Lawson, Tara Gancos Crawford, Clinton Moore
Adaptive harvest management (AHM) is a formalized framework that seeks improved management over time through the selection of recurrent harvest actions that serve, in part, to reduce key uncertainties about harvest dynamics. In an adaptive framework, management actions are frequently determined by a set of competing models that represent alternative hypotheses regarding the managed resource system. Models may be parameterized by data from monitoring programs designed to measure variables relevant to management decision-making. Over time, models that more successfully and consistently predict the outcome of management actions gain credibility, effectively reducing uncertainty among the models. AHM has been employed on a broad spatial scale to manage North American waterfowl populations for nearly 25 years and is widely considered a conservation success. In the southeastern United States, there is a growing interest in implementing an AHM framework to manage American alligators (Alligator mississippiensis). Both the role of harvest in regulating alligator populations (additive vs. compensatory mortality) and how variable policies (e.g., quotas, size class restrictions) affect demographic structure (e.g., age, size, and sex ratios) remain relatively unexamined; therefore, AHM could play an essential role in reducing systemic uncertainties, as successfully demonstrated in waterfowl. Here we discuss key differences in waterfowl and crocodilian population biology, and review existing alligator harvest policies among states in the eastern portion of the range. Lastly, we highlight how differences in biology, as well as temporal and spatial dimensions in management and monitoring methodology, are likely to promote differences in AHM frameworks for waterfowl and alligators.
4:20PM 8. Linking Conservation of Gamebirds and Threatened and Endangered Species to Achieve Multiple Habitat and Population Benefits
  Robert Clark, Lisha Berzins, James Devries, Kiel Drake
Conservation initiatives for gamebirds and species at risk are often planned and implemented separately but could be integrated, when appropriate, to achieve multi-species population objectives and attract support from a broader base of conservation supporters. Here, we examine the implications of large-scale habitat management initiatives targeted at prairie-nesting ducks for non-target bird populations. While loss of native grassland is a major concern across Canada’s Prairie Pothole Region (PPR) wetlands are a critical landscape feature underpinning biodiversity in the PPR. Here we focus on impacts to wetlands via private land management decisions (e.g., pond drainage) and climate variability that could diminish the PPR’s long-term capacity to support ducks. PPR ponds and adjacent uplands support diverse avian communities including songbird, marshbird and shorebird species of high conservation concern; thus, habitat programs that retain and restore wetlands for ducks also produce habitat benefits for these avian guilds and other taxa. PPR ponds may be even more important than previously recognized due to their potential to export highly nutritious aquatic insects to terrestrial birds. Using results from a 26-year study of individually-marked tree swallows (Tachycineta bicolor) –exemplary of an aerial insectivore – we demonstrate how nearly all components of swallow life-history are influenced by pond abundance. For example, earlier breeding and higher reproductive investment occurred in years of higher pond abundance. Furthermore, adult and first-year survival rates were positively associated with both food supply and(or) pond abundance. Importantly, path analyses revealed that lifetime reproductive success of female swallows was positively associated with pond abundance due to direct effects on offspring recruitment and indirectly via fledging success. Continued loss of ponds due to land use or climate change will have profound effects on demography of diverse species; conversely, conservation efforts that seek to retain and restore wetland basins will have wide-ranging positive impacts.
4:40PM 9. Longitudinal Data and Life-History Theory: How Should We Guide the Future of Gamebird Management?
  James Sedinger, Thomas Riecke, Benjamin Sedinger, Erik Blomberg
Gamebirds occupy a substantial range along the slow-fast life-history continuum, from bobwhite quail (annual survival < 0.2) to geese and swans (annual survival ~ 0.9 in the absence of harvest). Life-history theory predicts that harvest should have a greater impact on survival of species at the slow end of the spectrum, because annual survival in these species tends to have the greatest impact on fitness and is therefore “protected” from natural sources of mortality. Another way to think about this is that if only 10% of the individuals in a population die of natural causes each year there is less potential for harvest by humans to be offset, or compensated, by reductions in other sources of mortality. This prediction has been confirmed by several studies of geese, where relatively low harvest rates (< 5%) result in reductions of annual survival. Agreement with life-history theory is less clear for populations near the middle of the slow-fast spectrum (annual survival ~ 0.5) where some studies have reported that human harvest reduces annual survival while others report minimal or nonexistent effects of harvest on annual survival. Some authors have calculated from first principles that neither density dependence nor individual heterogeneity can produce substantial compensation for human harvest by other sources of mortality, which would be consistent with studies that have found an additive effect of harvest on total mortality. It remains to explain studies that have found weak or nonexistent relationships between human harvest and total mortality. We suggest that long-term demographic studies coupled with experimental or quasi-experimental manipulation of harvest and modern analytical approaches will help to resolve these questions.
5:00PM Panel Discussion
 

 
Organizers: Tessa Behnke, Erik Blomberg, Dan Gibson, Abigail Lawson, Marjorie Matocq, Ben Sedinger, Thomas Riecke, Amanda Van Dellen, Phillip Street
 

Symposium
Location: Reno-Sparks CC Date: October 3, 2019 Time: 1:10 pm - 5:00 pm