Browsing by Subject "Mark-recapture"

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    California spotted owl population dynamics in the central Sierra Nevada: an assessment using multiple types of data
    (2014-01) Tempel, Douglas John
    The California spotted owl (Strix occidentalis occidentalis) is a focal management species in the Sierra Nevada because it uses late-seral forests for roosting and nesting. Thus, obtaining accurate and precise estimates of population trends is necessary to reliably assess the effects of management actions and habitat change on this species. To demonstrate how this objective can be better met, I used multiple data types from a long-term population study in the central Sierra Nevada, as opposed to the typical approach of using only mark-recapture data. First, I compared population trends estimated from occupancy and mark-recapture data. Occupancy surveys are more cost-effective than mark-recapture studies for monitoring territorial species over large spatial extents. I found that the realized change in territory occupancy from 1993-2010 (&deltat = 0.702, 95% CI 0.552-0.852) closely matched the realized population change estimated from mark-recapture data (&deltat = 0.725, 95% CI 0.445-1.004). This suggested that occupancy can provide reliable inferences on population trends, especially when funds preclude more intensive mark-recapture studies. I recognize, however, that mark-recapture studies provide important demographic information not provided by occupancy studies, which may allow the identification of life-history stages that are limiting a population. Second, I developed an integrated population model (IPM) to obtain estimates of population change for my study population from 1990-2012 because IPMs may improve the precision of parameter estimates. My IPM incorporated count, reproductive, and mark-recapture data. I observed a significant population decline, as evidenced by the geometric mean of the finite rate of population change (&lambdat = 0.969, 95% CRI 0.957-0.980) and the resulting realized population change (proportion of the initial population present in 2012; &delta2012 = 0.501, 95% CRI 0.383-0.641). My IPM provided more precise estimates of realized population change than either the occupancy or mark-recapture analyses, but I did not account for covariance among the demographic rates in my IPM, which may have resulted in "false" precision (i.e., underestimation of the true variance). If covariances are incorporated into the IPM, they have excellent potential as a tool for assessing the status of species of conservation or management concern. My results also suggested that continued monitoring of this population and reconsideration of the California spotted owl's status under the U. S. Endangered Species Act may be warranted.
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    The causes and consequences of individual variation in survival and fecundity of Great Lakes piping plovers (Charadrius melodus)
    (2015-03) Saunders, Sarah Prairie
    The piping plover (Charadrius melodus) is a small shorebird endemic to North America and restricted to three breeding populations: Atlantic Coast, Great Plains, and Great Lakes. Listed as federally endangered in 1986, the Great Lakes population has numbered from 17 to 71 known breeding pairs. Despite recovery efforts, the population is far from the federal recovery goal of 150 breeding pairs. The purpose of my dissertation research is to understand the causes and consequences of individual variation in survival and fecundity during key breeding stages through four distinct methods of investigation: life-history theory, quantitative genetic analysis, population demography, and behavioral assessment. Effective conservation of small wildlife populations requires the intersection of many scientific disciplines and I seek to achieve this unification through the four chapters of my dissertation. First, I investigate how age and parental experience with breeding, a mate, and a nesting location influence reproductive success (Chapter 1). In chapter 2, I investigate the heritabilities of three fitness-related traits (chick body mass, natal dispersal distance, and female timing of breeding) to determine which are strongly environmentally-determined and thus susceptible to impacts of global climate change. In chapter 3, I tease apart the relative influences of various developmental and environmental factors at pre-fledging, post-fledging, and adult stages to more precisely inform population recovery actions. In my final chapter, I test the hypothesis that captive-reared chicks have lower survival rates than those reared in the wild because of a lack of threat recognition. The insights gained from my research not only pertain to this small shorebird breeding in the Great Lakes, but also provide a more comprehensive framework for analyzing data on marked individuals with the goal of shaping conservation actions for an entire population. Further, the new analytical methods applied to ecologically complex data will be important to any study that uses long-term marking. Avian populations are predicted to become more threatened in the future, so it is increasingly critical to understand factors driving vital rates and to develop approaches to alleviate threats to population persistence.