I investigated the effect of energy sector development and introduced crested wheatgrass (Agropyron cristatum) on grassland birds on Canadian Forces Base Suffield. I conducted point counts and mapped breeding territories in 2007 and 2008 for Savannah sparrows (Passerculus sandwichensis), chestnut-collared longspurs (Calcarius ornatus), and Spragues pipits (Anthus spragueii). I found that Savannah sparrows favored areas with taller vegetation, human disturbances and crested wheatgrass in both years. Longspurs used shorter vegetation and in were tolerant of disturbance. Crested wheatgrass was avoided by longspurs in both years. Pipit territories contained similar vegetation to longspurs, were sensitive to disturbance, and avoided placing territories in areas containing crested wheatgrass or trails in both years. Well sites, pipelines and junctions were not avoided by the three species. My research suggests that reducing the number of trails and the spread of crested wheatgrass will increase habitat availability for sensitive species of grassland birds. / Ecology

Habitat selection theory presumes that organisms are not distributed randomly in their environments because of habitat-specific differences in reproductive success and survival; unfortunately, many previous studies were either unable or failed to look for evidence of processes shaping nest site selection patterns. Furthermore, little is known about adaptive nest site selection in northern environments where habitats often have little vegetation and time and climatic constraints may be pronounced. Therefore, I investigated patterns of nest site selection by common eider ducks (<i>Somateria mollissima</i>) at an island colony in Canadas Eastern Arctic, and looked for evidence of selective processes underlying these patterns by employing experimental and observational techniques.<p>I characterized physical features of (a) non-nest sites (b) active nest sites and (c) unoccupied nest sites that had been used in previous years. Habitat features that distinguished non-nest sites from unoccupied nest sites were also important in distinguishing between active and unoccupied nest sites during the breeding season. Active nest sites were closer to herring gull (<i>Larus argentatus</i>) nests, farther from the ocean and had organic substrates. In general, habitat features associated with nest use were not strongly associated with success after the onset of incubation. Nests near fresh water ponds were more successful in one study year, but in the other two study years successful nests were initiated earlier and more synchronously than were unsuccessful nests. Common eiders settled to nest first near the geographic centre of the colony, whereas sites near the largest fresh water pond were occupied later; distance to ocean had no observable effect on timing of nesting. Nest density was greater farther from the ocean, but timing of nest establishment did not differ between high and low density plots. <p>I tested whether moss or duck down placed in nest bowls could increase nest establishment, or advance laying date. I placed this extraneous material in bowls before nesting and found no difference in likelihood of nest establishment; however, bowls containing duck down were initiated earlier (or had higher survival) than those containing no nesting material. To investigate the role of nest shelter and microclimate in nest site choices and female body condition, I placed plywood nest shelters over established nests. Temperature probes indicated that artificially-sheltered females experienced more moderate thermal environments and maintained higher body weight during late incubation than did unsheltered females. However, few eiders nested at naturally-sheltered sites, possibly because nest concealment increases susceptibility to mammalian predators. My results suggest that eider nest choices likely reflect trade-offs among selective pressures that involve the local predator community, egg concealment, nest microclimate and energy use.

Habitat selection theory presumes that organisms are not distributed randomly in their environments because of habitat-specific differences in reproductive success and survival; unfortunately, many previous studies were either unable or failed to look for evidence of processes shaping nest site selection patterns. Furthermore, little is known about adaptive nest site selection in northern environments where habitats often have little vegetation and time and climatic constraints may be pronounced. Therefore, I investigated patterns of nest site selection by common eider ducks (<i>Somateria mollissima</i>) at an island colony in Canadas Eastern Arctic, and looked for evidence of selective processes underlying these patterns by employing experimental and observational techniques.<p>I characterized physical features of (a) non-nest sites (b) active nest sites and (c) unoccupied nest sites that had been used in previous years. Habitat features that distinguished non-nest sites from unoccupied nest sites were also important in distinguishing between active and unoccupied nest sites during the breeding season. Active nest sites were closer to herring gull (<i>Larus argentatus</i>) nests, farther from the ocean and had organic substrates. In general, habitat features associated with nest use were not strongly associated with success after the onset of incubation. Nests near fresh water ponds were more successful in one study year, but in the other two study years successful nests were initiated earlier and more synchronously than were unsuccessful nests. Common eiders settled to nest first near the geographic centre of the colony, whereas sites near the largest fresh water pond were occupied later; distance to ocean had no observable effect on timing of nesting. Nest density was greater farther from the ocean, but timing of nest establishment did not differ between high and low density plots. <p>I tested whether moss or duck down placed in nest bowls could increase nest establishment, or advance laying date. I placed this extraneous material in bowls before nesting and found no difference in likelihood of nest establishment; however, bowls containing duck down were initiated earlier (or had higher survival) than those containing no nesting material. To investigate the role of nest shelter and microclimate in nest site choices and female body condition, I placed plywood nest shelters over established nests. Temperature probes indicated that artificially-sheltered females experienced more moderate thermal environments and maintained higher body weight during late incubation than did unsheltered females. However, few eiders nested at naturally-sheltered sites, possibly because nest concealment increases susceptibility to mammalian predators. My results suggest that eider nest choices likely reflect trade-offs among selective pressures that involve the local predator community, egg concealment, nest microclimate and energy use.

Northern bobwhites (Colinus virginianus) are an important cultural, ecological, and economical part of the southern Texas landscape. I used radio-telemetry data from 2000?2005, part of a long-term, bobwhite study in southern Texas, to test the nest-concealment hypothesis, develop a stochastic simulation model for bobwhite populations, and evaluate the influence of brush canopy coverage (BCC) on short- and long-term demographic performance of bobwhites. Bobwhite nests tend to be situated in taller and denser vegetation than would be expected if nest-site location was a random process. I compared 4 microhabitat variables between successful (n = 135) and depredated nests (n = 118). I documented similar microhabitat attributes between successful and depredated nests. The discriminant function correctly classified only 48?59% of nest fates into the correct group, but only 18% of the variation in nest fate. Thus, my results did not support the nest-concealment hypothesis. My stochastic simulation model for bobwhite populations is based on difference equations (?t = 3 months) and simulations run for 100 years using STELLA� 9.0.2. The probability of persistence for 100 years for the spring population was 74.2% and 72.5% for the fall population. Simulated population parameters were similar to those observed in the field for 5 of 6 population parameters. Only simulated male adult annual survival differed by 275.0% from field estimates. Despite this difference, my model appears to be a good predictor of bobwhite populations in the Rio Grande Plains of Texas. I estimated bobwhite density, survival, and production (proportion of hens nesting, nesting attempts per hen, and clutch size) in 3 study areas with ~10%, ~25%, and >30% BBC. All demographic parameters were similar among the 3 BCC classes. However, simulation modeling indicated that long-term demographic performance was greater on the ~25% and >30% BCC classes. The probability of fall population persistence was greater in the ~25% (90.8%) and >30% (100.0%) BCC classes than in the ~10% BCC class (54.2%). My study highlights the shortcoming of considering only short-term effects when comparing habitat given that short- and long-term effects of habitat on demographic performance can differ.

No description available.

Doctor of Philosophy / Department of Biology / Brett K. Sandercock / Sexual selection via female choice and male-male aggression leads to elaboration of male traits. If male traits correlated with reproductive success are honest signals of male quality, survival costs may be associated with the expression of those traits. Testosterone (hereafter ‘T’) may enhance male breeding success, but T can also reduce immunocompetence and survival. Socially monogamous male birds with higher circulating T experience reproductive advantages, but the role of T in lek mating systems is largely unknown. To address these issues, I individually marked and conducted focal behavioral observations of greater prairie-chickens (Tympanuchus cupido) at five lek sites over a 5-year period. Females were fitted with radio-telemetry to monitor nesting success and survival. I examined the relationship between male traits and mating success using multinomial discrete choice models, a statistical method not previously applied to studies of sexual selection. Male mating success was highly skewed at greater prairie-chicken leks with 18.5% of males obtaining 87.2% of all successful copulations (n = 108 males; 85 copulations). Mating success was influenced most by male behavior, followed by several morphological attributes. The role of T was quantified using blood samples and by experimentally implanting a subset of males with T. T did not consistently affect mating success. Non-territorial males had lower T levels than territorial males. Among territory holders, T was unexpectedly negatively correlated with mating success. However, the odds of receiving a copulation were 4.3 times (0.42 to 45.3) greater for T-implanted males than males with sham implants. Future work should explore the interactions among the immune system, parasite load, and mating success of prairie-chickens. Annual survival of male prairie-chickens was not related to mating success, behavior, age or T level, suggesting there is no cost of increased male mating success. Like males, reproductive success of females was also highly skewed because < 10% of nests successfully hatched young. Comparisons of seasonal and annual survival rates indicate that females experience increased mortality during the breeding season relative to the nonbreeding season. Synthesis of field estimates of demographic parameters indicates prairie-chicken populations will decline without changes in rangeland management to reduce predator numbers or provide more nesting cover.

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.

No description available.