Factors Influencing Next Success of Reintroduced Whooping Cranes (Grus americana) in Wisconsin
Jaworski, Jessica A.
University of Wisconsin-Stevens Point, College of Natural Resources
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The data presented in the chapters of this thesis are primarily focused on examining factors influencing the reproductive success of the federally endangered Eastern Migratory Population (EMP) of whooping cranes (WHCR, Grus americana) that chiefly nest at the Necedah National Wildlife Refuge (NNWR) in Juneau County, Wisconsin and the Meadow Valley State Wildlife Area (MVSWA) in Monroe County, Wisconsin. Data were collected from the 2014 through 2016 breeding seasons. Reproductive success of adult WHCR’s in the EMP is near 0% and nearly all breeding adults have been raised in captivity by costumed humans. We do not know how captive rearing has affected the reproductive success of EMP WHCR’s and do not have data to compare EMP WHCR’s to the only wild, self sustaining Aransas Wood Buffalo Population (AWBP) of WHCR’s. However, because other studies have used a related species to make comparisons between captive raised and wild individuals to aid in endangered species management (Powell et al. 1997), we used greater sandhill cranes (SACR, Grus canadensis tabida) as a surrogate species because they also nest at NNWR and MVSWA. In the first chapter, we examined the response of WHCR’s and SACR’s to a human induced nest disturbance by examining the flight initiation distance (FID) and duration of time spent off nest (TON) following the disturbance. We evaluated potential differences in FID and TON between WHCR’s and SACR’s nesting on and around NNWR with regard to age of clutch, disturbance method (i.e. on foot, kayak, or canoe), ordinal day of the year, and species. We used linear regression and ranked models using AICc corrected for small sample size for model selection. The best approximating model for FID included a species covariate and contained 99 % of the total AIC weight. Results for TON were ambiguous and AIC weights were relatively evenly distributed. However, our results indicate a species effect of FID and TON between WHCR’s and SACR’s nesting on and around NNWR. Whooping cranes had greater flush distances and returned to nests sooner than SACR’s. The majority of data we collected involved using trail cameras and required multiple observers to identify behaviors from camera photos. In the second chapter, we investigated the effects of training on inter-observer reliability when examining camera photos. We assessed factors that may influence the reliability of observers identifying distinct behaviors of nesting cranes including the complexity of behavior, species being observed and the training level of the observer. We used logistic regression and ranked models using AICc corrected for small sample size. The best approximating model included an interaction of training and complexity and contained 99 % of the total AIC weight. Our data indicate that training increases inter-observer reliability. However the positive effects of training were only recognized when specific, complex behaviors were being identified. Ornithophilic black fly emergence coincides with WHCR incubation on and around NNWR. Black fly emergence may be a contributing factor for the low reproductive success of EMP WHCR’s and has been identified as a cause for widespread, synchronous nest abandonment. Nest abandonment due to black fly parasitism is not observed in SACR’s nesting near WHCR’s on and around NNWR. Therefore, in the third and final chapter, we compared incubation behavior between SACR’s and WHCR’s during and after black fly emergence by installing trail cameras at active nests. In addition, we aimed to reduce black fly duress on incubating WHCR’s via egg salvage induced nest failure and to identify if egg salvaged induced nest failure increases WHCR renest propensity. We quantified the percent time nesting cranes spent exhibiting various incubation and black fly avoidance behaviors and ran a discriminant function analysis on the average proportion of time spent per nest to compare incubation behaviors by species and fate of nest. Our data suggest that behavior indicative of black fly emergence was more prevalent at failed WHCR nests. Our results also indicate WHCR’s that nested later are more successful than ones that nested during black fly parasitism suggesting renesting without the presence of black fly parasitism could increase WHCR nest success.