Browsing by Subject "integrated population model"

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    Ecology and Conservation of Common Terns (Sterna hirundo) Breeding in the North American Great Lakes Region
    (2021-05) Bracey, Annie
    The common tern (Sterna hirundo) is a long-distance migratory waterbird that breeds in both freshwater and marine environments in many parts of the world. Although the most wide-spread tern species in North America, populations have experienced extreme fluctuations during the last half century, with significant declines documented in the Great Lakes region and other inland breeding sites. Because of their reliance on coastal habitats, population declines have often been attributed to direct and indirect effects of human activity, such as habitat loss, modification, and degradation. In the Great Lakes most active breeding colonies occur at managed sites. The goal of my dissertation research was to document population dynamics of common terns breeding in western Lake Superior to understand how movement and demographic parameters vary between colonies and among colonies outside the region. A variety of intrinsic and extrinsic tagging methods were used to follow individuals throughout their annual cycle to identify potential risks to survival and fitness. Each chapter identifies potential risks to the population at different life stages and at different spatial and temporal scales. The first chapter documents large-scale movement patterns of adults breeding in the ‘central population unit’ using solar geolocation tracking devices to identify important migratory routes and wintering locations. Chapter 2 examines how adult foraging behavior influences mercury exposure in adults and chicks, to estimate exposure risk for birds nesting in western Lake Superior. Chapter 3 uses 36 years of mark-recapture data to identify drivers of population change by estimating survival, fecundity, and local-scale movements of adults and juveniles in western Lake Superior. These results filled gaps in knowledge about basic life history of Great Lakes nesting Common Terns and identified multiple potential risks (e.g., conditions at important stopover and non-breeding locations, especially coastal Peru, contaminant exposure at industrially-influenced breeding sites) to this population which can be mitigated through targeted conservation and management actions. Because climate change is expected to exacerbate these threats, it is imperative that suitable nesting habitat be restored and maintained for common terns breeding in the Great Lakes region, especially in the face of future environmental uncertainty and an ever-changing landscape.
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    Estimating annual harvest of American Woodcock (Scolopax minor) in the United States during 1964-2016: data, model code, and supplemental estimates
    (2019-07-09) Arnold, Todd W.; Farr, Matthew T.; Wright, Alexander D.; Saunders, Sarah P.; arnol065@umn.edu; Arnold, Todd W.; Department of Integrative Biology, Michigan State University (MTF, ADW, SPS); Department of Fisheries, Wildlife and Conservation Biology, University of Minnesota (TWA)
    Harvest of American woodcock (Scolopax minor) in the United States has been estimated using two different hunter surveys: 1) the Duck Stamp Survey (DSS, 1964-2001), which estimated harvest by hunters who also hunted ducks or geese and purchased a Federal Migratory Bird Hunting (“Duck”) Stamp, but failed to survey hunters who did not purchase Duck Stamps (which were not required for hunting woodcock); and 2) the Harvest Information Program (HIP, 1999-2019), which was initiated in 1999 and designed to survey nearly all hunters who targeted woodcock. The two surveys overlapped during only 3 years (1999-2001), and in most states, the HIP survey estimated much higher woodcock harvest based on its more complete sampling frame of woodcock hunters. We developed Bayesian hierarchical models to use combined data streams to estimate total harvest during 1964-2016 (Arnold 2019) or 1964-2013 (Saunders et al. 2019) in the Eastern and Central Management Units by estimating unobserved harvest by hunters who never or only occasionally hunted waterfowl. Both approaches used annual Duck Stamp sales as a covariate to assess annual participation by hunters who occasionally hunted waterfowl, and also used the 3 overlap years (1999-2001) to estimate harvest by hunters who never hunted waterfowl. However, our approaches differed in how we assessed participation by occasional waterfowl hunters: 1) as residuals from splines fit to long-term duck stamp sales (Arnold 2019), which posited a smooth change in total waterfowl hunters through time, with residuals reflecting short-term participation or non-participation in waterfowl hunting, or 2) relative to maximum annual duck stamp sales (Saunders et al. 2019), which posited a constant number of potential waterfowl hunters in each state (max stamp sales), but with annual changes in relative participation in waterfowl hunting corresponding to yearly stamp sales. Our estimates were remarkably similar for combined harvest in the Central Management Unit, but diverged substantially for the Eastern Management Unit. We have no way of assessing which set of assumptions is closer to the truth, and present both models here in hopes that future researchers will continue to refine our methods to produce even more robust estimates of historical woodcock harvest.