Nest success of dabbling ducks in the Prairie Pothole region of North America has been declining for the past 40 years in parallel with declines in duck populations. Low nest success seems to result from the combination of an extremely fragmented breeding ground in a human-dominated landscape with an abundant and expanding ii community of generalist nest predators. Studies that examined variables associated with nest vulnerability to predation have produced contradictory results, likely because of simplistic approaches, lack of spatio-temporal replication, use of artificial nests , and the effect of confounding variables. I attempted to clarify the equivocal findings of previous studies by using multiple regression to simultaneously examine the effect of several variables purportedly related to nest predation risk. I collected data on >1,800 dabbling duck nests and associated variables for 16 habitat patches (14 managed for duck production) during two nesting seasons in North Dakota. At the habitat patch level, early and late in each breeding season, I studied the relationship of nest success and upland area, nest density, predator abundance and richness, abundance of alternative prey for predators, and visual and physical obstruction provided by the vegetation . At the spatial scale of the nest and its neighborhood, I examined the likelihood of nest predation in association to nest initiation date, year, distance from nest to a wetland and to an edge, vegetation type at the nest, visual obstruction and heterogeneity of the vegetation around the nest, duck nest species , predator abundance, and presence/absence of 5 carnivorous predators at the nest habitat patch. Nest success was generally low and highly variable in time, and among and within habitat patches. I found no relationship between nest success and any of the variables measured at the patch scale. At the nest level, only initiation date, distance to water, visual obstruction, predator abundance, and duck species had an effect. High variability in the data and the lack of patterns in the relationship of nest predation and the predictor variables precluded me from building a predictive model that explains nest success. Nest success could not be predicted, predation was incidental and risk was high, and there were no safe nest sites for hens to choose in a landscape swamped by nest predators . Nests were located randomly; therefore, there were no clues predators could use to enhance their success in finding nests.

Anthropogenic perturbations to Arctic ecosystems have influenced large-scale climate processes, as well as finer-scale ecological relationships within and amongst populations of species. Life history theory predicts a trade-off between the temporal variation in a vital rate and its impact on population dynamics. Here, we examine the drivers of long-term variation in reproductive success in a sub-Arctic common eider (Somateria mollissima) colony, and evaluate the impacts of variation in reproductive success on eider population dynamics. In Chapter 2, we develop a suite of nest survival models to evaluate the effects of variation in predator abundance, the availability and spatial distribution of alternative prey, and breeding season climate on annual common eider nest success. Eider nest success declined across the 41 years of study, but was also highly variable across years. Annual variation in nest success was driven by a complex interaction between predators and alternative prey, as well as breeding season climate. Our results suggest that increased abundance of snow geese (alternative prey) may buffer annual fluctuations in arctic fox abundance, yet result in a long-term decline in eider nest success suggesting apparent competition via other predator species (e.g. gulls). The effect of breeding season climate was subtle compared to the influence of biotic factors and indicated that cold, wet conditions in early spring were correlated with decreased nest success, while warm, wet conditions in late spring increased eider nest success. In Chapter 3 we develop a stochastic population model to evaluate the relative effects of variation and covariation amongst multiple vital rates on population dynamics, and determine the impact of long-term changes in the abundance of alternative prey on eider population dynamics. Consistent with life history predictions, we found that proportional changes in adult survival have the largest impact on population dynamics, yet high variation in the vital rates underlying fertility contribute more to actual variation in population growth. The eventual exodus of alternative prey from the eider colony reduced the long-term growth rate, primarily through negative impacts on mean nest success.

The decline of greater sage-grouse (Centrocercus urophasianus) populations across western North America has intensified conservation, research, and management efforts. Predator-prey interactions have been the focus of widespread scientific study, but little research has been conducted on the effects of predation and predator removal on sage-grouse ecology. This study had three main objectives: 1) identify the types of predators impacting hen survival and nest success, 2) compare the effect of predator removal on vital rates, and 3) evaluate habitat selection and movement. Over two years (2011-2012), an observational study and field experiment were used to test the effects of predation and predator removal on sage-grouse survival, nest success, and spatial ecology in Bighorn Basin, Wyoming. In year one, I quantified the impacts of predators on sage-grouse demographics and developed a basis for monitoring sage-grouse and predator populations. In year two, predator removal was modified to remove the primary nest and hen predator in this system: coyote (Canis latrans). I evaluated the impact of anthropogenic features and management on sage-grouse home range size, seasonal movement, and habitat selection for potential behavioral responses. Resource selection functions (RSFs) were used to determine habitat selection and identify differences at multiple spatial extents (seasonal and annual scales). Hen survival was improved in sites treated with coyote removal over the nesting period (P = 0.05) but no improvement was seen in annual hen survival (P = 0.19). Observed nest success was higher at the site without coyote removal (P < 0.0001). RSF modeling showed sage-grouse to be sensitive to predator removal, avoiding areas close to roads, with high well density, and steep slopes. While this study suggests predator removal does not benefit observed nest success, provides only short-term enhancement to survival, and may disrupt habitat selection, potentially benefits to other life stages could exist and be detected with more time and monitoring. By taking an experimental approach to examining the effects of predation and predator removal, this study advances our knowledge of sage-grouse ecology by identifying changes in demographic vital rates and habitat selection, propagating the best management possible for sage-grouse populations.

Development and climate change in the sagebrush habitats are causing population declines of North American hawks and eagles. For these species, understanding the landscape features that are preferred for nesting and the prey they consume in sagebrush habitats are important in developing conservation plans. Specifically, we know little of the preferred nest-sites and diet of Ferruginous Hawks (Buteo regalis) and Golden Eagles (Aquila chrysaetos) many locales. In our study, we determined the landscape characteristics associated with nest sites for these two raptor species in the Uintah Basin, UT to predict where nests may occur in our study area. We found that slope, elevation, distance to nearest oil and gas wells, geology, and facing south were the most important variables in characterizing Golden Eagle nest-sites. Elevation, slope, vegetation type, and distance to nearest oil and gas wells were the most important variables in characterizing Ferruginous Hawk nest-sites. In addition, we looked at the diets of Golden Eagles, Ferruginous Hawks, and Northern Goshawks in the Uinta Basin, UT using a genetic analysis method novel to raptors. We found species consistent with previous diet studies and detected prey items not previously reported, including the Western Whiptail (Aspidocelis tigris), Domestic Cow (Bos Taurus), Domestic Pig (Sus scrofa), and Rock Bass (Amboplites rupestris) within Ferruginous Hawk samples. Results from our study can provide managers with tools to better survey for nest-sites and to provide an alternative method of diet analysis to provide insight into prey species important to these raptors.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20445号 / 農博第2230号 / 新制||農||1050(附属図書館) / 学位論文||H29||N5066(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 吉村 剛, 教授 藤井 義久, 教授 松浦 健二 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Cyclura ricordii is an endemic iguana from Hispaniola and is listed as Critically Endangered on the IUCN. The main threats are predation by introduced mammals, habitat destruction and hunting. The present study focused on two nesting areas in Pedernales in the Dominican Republic. The hypothesis tested is that natal philopatry influences dispersal and nest site selection. Monitoring and sampling took place during 2012-2013. Polymorphic markers were used to evaluate whether natal philopatry limits dispersal at multiple spatial scales. Ripley’s K, revealed that nests were significantly clustered. Hierarchical AMOVA revealed that nest site aggregations did not explain a significant portion of genetic variation. However, Mantel’s tests revealed significant positive correlations between genetic and geographic distance. These results indicate that natal philopatry limits dispersal at a course spatial scale, but does not influence nest site selection at a fine spatial scale.

Growing concerns about climate change, foreign oil dependency, and environmental quality have fostered interest in perennial native grasses (e.g. switchgrass [Panicum virgatum]) for bioenergy production while also maintaining biodiversity and ecosystem function. However, biofuel cultivation in marginal landscapes such as airport grasslands may have detrimental effects on aviation safety as well as demography and conservation efforts for grassland birds including Dickcissels (Spiza americana). In 2011–2013 I studied the response of avian populations to vegetation composition and harvest frequency of switchgrass monocultures and native warm-season grass (NWSG) mixtures at B. Bryan farms in Clay Co. MS, USA. Four treatments incorporating switchgrass and NWSG with single and multiple annual harvesting were established on 16 experimental plots. I examined the relative abundance, aviation risk, and conservation value of birds associated with these treatments, evaluated contributions of habitat attributes and individual male quality towards territory productivity and determined effects of harvest regimens on nest success, nest density, and productivity for Dickcissels. Avian relative abundance was greater in switchgrass plots during winter months, whereas NWSG was favored by species during the breeding season. Conversely, treatment differences in aviation risk and conservation value were not biologically significant. Only 2.6% of observations included avian species of high risk to aircraft, suggesting that it may be feasible to use semi-natural grasslands at airports to provide grassland bird habitat while concurrently minimizing aviation risk. Regarding individual and habitat quality effects on nest survival and productivity, male song rate was not an effective surrogate for individual quality in demographic models. However, nest survival declined with increasing territory size and territories established earlier in the season had greater territory productivity relative to later arriving males, providing evidence that some metric of individual quality is important for grassland bird reproduction. Additionally, vegetation composition and harvest frequencies influenced nest density and productivity, but not nest survival. Native warm season grasses contained 54–64 times more nests relative to switchgrass treatments, and nest density was 10% greater in single harvest plots. My results suggest semi-natural grasslands can support grassland bird conservation while allowing for biofuel production and aviation risk management in airport landscapes.

Imported fire ants are invasive and cause injury to people, crops, livestock and wildlife. Disturbance may increase abundance and activity of fire ants. However, native grass field buffers established for grassland birds require periodic disturbance. I experimentally tested if fire ant mound density and foraging activity changed after burning and disking in native grass buffers and examined relationships among fire ants, vegetation, and grassland bird and butterfly metrics in undisturbed buffers. In 2008, disking increased mound density and foraging activity, but burning did not. In 2009, disking had no effect, but effects of disking the previous season persisted. Fire ant metrics were not related generally to bird or butterfly metrics. Mound density and foraging activity were related negatively to grass cover and related positively to forbs. Burning had less influence on abundance and activity of fire ants, and may better conserve grassland habitats in areas with fire ants.

Few studies have measured the impacts of mowing on bird use of habitat and the risk of bird collisions with aircraft on North American airfields. The need for this research has increased as airfields become some of the only large contiguous grasslands available to rare migratory birds in some areas. I studied bird abundance, distribution and behaviors at Westover Air Reserve Base, Massachusetts, USA in June and July 2004. I compared my data with bird strike records to discern any patterns associated with mowing of airfield vegetation. There was no difference in total number of birds or species between mowed and unmowed plots adjacent to runways and taxiways. There were more Upland Sandpipers and Eastern Meadowlarks in mowed vegetation and more sparrows (Grasshopper and Savannah) in unmowed vegetation. From 1997 to 2005, swallows were the birds most often struck by aircraft in June and July at Westover, and were also the second most numerous birds in both mowed and unmowed plots. Bird species that pose high Bird/Wildlife Aircraft Strike Hazard (BASH) risk at Westover included Turkey Vulture, Red-tailed Hawk, Great Blue Heron, and Canada Goose. I did not observe those species in paired plots of mowed or unmowed airfield vegetation adjacent to runways and taxiways at Westover. I opportunistically observed 64 incidents where species that pose high BASH risk were in or adjacent to areas where aircraft operate. Birds struck most frequently at Westover between April 1997 and January 2005 were “swallows”, American Kestrel, Killdeer, Horned Lark, Eastern Meadowlark, and Mourning Dove. Current mowing practices at Westover may have adverse effects on Upland Sandpiper and Grasshopper Sparrow, both state-listed, rare, grassland birds, but may not measurably reduce overall risk to aircraft, given the continued presence of large, high BASH risk species. I recommend methods to reduce threats posed by high-risk species at Westover, and further research to seek ways to reduce adverse effects of mowing on state-listed, rare, migratory species of birds.

The reproductive success of the Purple Martin is dependent upon many factors. This study measured reproductive success of the Purple Martin (Progne subis subis) based on parental age and type of housing used. Reproductive parental ages consist of adults (experienced breeders) and subadults (first time breeders). Housing types included in this study were aluminum housing, wooden housing, plastic gourds, natural gourds, SuperGourds, and mailbox housing. The reproductive success was defined as the percentage of the original clutch that fledged. Study sites were located in Alabama, Indiana, North Carolina, Oklahoma, Tennessee, and Virginia. Pairs mating nonassortatively by age group had lower reproductive success than adults and subadults that were paired assortatively. Purple Martins were the most reproductively successful in SuperGourds and the least reproductively successful in wooden housing. This study provides evidence that may be basis for further research, help support the conservation of the Purple Martin, and aid reproductive success on its breeding grounds.