Interior Double-crested cormorant reproduction was examined on a large geographical scale to evaluate management actions. Three distinct breeding areas across Ontario were selected. Beginning in 2002, over 11,000 preledged cormorants have been marked. During 2006 and 2007, re-observation of banded birds, colony data such as nest, egg, and chick measurements, and island morphology, were collected. Data revealed no significant regional differences in adult size. However, eggs in eastern Lake Ontario (ELO) were larger than North Channel of Lake Huron (NChan) and Lake of the Woods (LOW). Chicks in ELO throughout development were smaller than NChan and LOW. Number of gulls was correlated inversely to cormorant fledge rate. Survival estimates were <20% for young of the year, but increased to >80% after year 2. Elasticity analysis revealed that a 50% reduction in adult survival combined with 100% fecundity reduction would result in a 42% reduction in population growth.

Double-crested cormorants have steadily increased in the Mississippi Delta. This bird serves as a definitive host for digenetic trematodes, many of which infect fish. To identify these digeneans in cormorants and determine the impact these infections have on wild fish in the Mississippi Delta, two surveys were done. Cormorants were collected for two years in the Mississippi Delta. At necropsy trematodes were collected and identified morphologically and molecularly as: Austrodiplostomum ostrowskiae, Hysteromorpha triloba, Drepanocephalus spathans, Ascocotyle longa and Pseudopsilostoma varium. Additionally, 14 fish species were collected from a Mississippi Delta lake. Fish were examined for parasites and Posthodiplostomum minimum metacercariae were found in multiple organs in 6/14 fish species. The 18S gene sequences of these metacercariae were identical to published P. minimum sequences, whereas the cytochrome oxidase I (COI) sequences matched published COI sequences for Posthodiplostomum sp. 3, 5 and 8, suggesting subspecies of Posthodiplostomum in this fish population.

Cheatgrass is an invasive weed that has come to dominate large areas of the western United States. Once an ecosystem has been converted to a cheatgrass monoculture, it is extremely difficult to restore native vegetation. Cheatgrass negatively impacts wildlife and increases wildfire frequency and intensity. Understanding how cheatgrass so effectively invades western ecosystems is essential to turning the tide of invasion. One possible key to cheatgrass’ success is alteration of soil nutrient cycling. The goal of this study is to explore how nitrogen (N) may accumulate in cheatgrass soils via redistribution of N within soil N pools. To accomplish this we investigated soil N cycling in soils underneath cheatgrass and crested wheatgrass. We used a 15N isotope tracer to determine the contribution of root exudates to soil N pools. During the 1-week 15N tracer experiment, cheatgrass roots exuded more than twice as much N (0.11 mg N kg-1 soil d-1) as crested wheatgrass roots (0.05 mg N kg-1 soil d-1). We propose that exudation of high N content root exudates leads to the changes in soil N pool size and transformation rates commonly observed in soils under cheatgrass. This research uses a simple and relatively inexpensive isotope tracer to shed light on mechanisms by which invasive plants may alter soil processes. By understanding these mechanisms we may be able to develop strategies for better managing cheatgrass invasion.

The free-roaming ruminant requires energy for the demands of vii grazing, traveling and thermoregulation that are not required by its confined counterpart. Literature estimates of these additional costs range from 10 to 170 percent above maintenance. The uncertain magnitude of this increased demand and the factors that contribute to it impede the ability of the rangeland ruminant nutritionist to establish guidelines for the energy requirements of the free-roaming herbivore. This study was designed to estimate the energy expenditure of yearling Angus heifers while grazing a declining supply of available crested wheatgrass forage (Agropyron cristatum) on rangeland in west-central Utah. Free-ranging energy expenditure was estimated twice for four heifers during each of five ten-day periods during June, July August and early September, 1979. These estimates were obtained using the carbon dioxide entry rate technique. In addition, total fecal output, dietary crude protein and dietary in vitro organic matter digestibility were estimated for animals grazing the 20- hectare crested wheatgrass pasture. From these data, daily forage intake was calculated. The level of available forage during each period was estimated using the ocular weight-estimate technique applied on forty 1 m2 circular plots. Energy expenditure was estimated as 161 (with a confidence interval of ±43) kcal·kg body weight-.75.d-1 (n=10), and was independent of the decline in available forage from 880 to 284 kg dry matter·hectare-1 that occurred over the course of the grazing season. Daily intake was 54.5 grams (organic matter basis) per unit body weight.75 for the 305 kg heifers. Daily intake was independent of the supply of available forage. During early July, 1980, crested wheatgrass was harvested as hay and fed to 260 kg yearling Angus heifers in metabolism stalls in a thermoneutral and constantly illuminated laboratory. Daily feeding levels were set at 54.5 grams (organic matter basis) per unit body weight.75. Energy expenditure under these conditions was estimated as 111 (±12) kcal·kg body weight-.75·day-1 , 6 kcal per unit body weight.75 greater than the mean estimate of the fasting metabolism rate. The latter estimate was obtained following a 48-hour fast. These estimates of maintenance and fasting metabolism were combined to provide a mean estimate of 110 (±10) kcal·kg body weight-.75·day-1 (n=14). Of the 45 percent (51 kcal·kg body weight-.75·day-1) increase in the estimated energy expenditures by heifers under free-roaming conditions, 50 percent was attributed to the energetic cost of grazing. A daily average 9.2 hours were spent in this activity. The energetic cost of grazing was assumed as 0.82 kcal·kg body weight-1·hour-1 spent grazing. Daily travel was estimated as 3.9 km at an assumed energetic cost of 0.58 kcal·kg body weight-1·km-1. This accounted for a 20 percent estimated increase in energy expenditure. Average daily temperatures were generally between 12°C and 30°C and thermoregulatory demands were not considered as a substantial energetic expense. The remaining 30 percent (12 kcal) of the additional increment due to free-roaming conditions could not be explained.

Complementary greenhouse and field studies investigated the effects of ambient environmental conditions on cattle dungpat moisture, temperature, nutrient concentration, and crust formation dynamics, which in turn influence seed germination and seedling establishment in dungpats. 'Hycrest' crested wheatgrass [Agropyron desertorum (Fisch. ex Link) X A. cristatum (L.) Gaert.] was used as a representative revegetation species. After collecting feces from Holstein steers that had been fed crested wheatgrass seeds, uniform dungpats were prepared and placed on two soil types (loam and coarse sand) in containers under three watering treatments (field capacity, 1/2 field capacity, and no water) in the greenhouse. Dungpat and underlying soil microenvironmental factors, and germination and seedling development, were monitored for 14 weeks. Moisture and temperature were favorable for germination during the first 4 weeks, but increasing crust thickness prevented most of the developing seedlings from emerging from dungpats. Seedling emergence, development, and survival were greatest at the peripheral region of dungpats on the loam soil at moisture contents of 1/2 field capacity or higher. Uniform dungpats containing passed seeds and unpassed seeds were placed on a silt loam soil in the field in the spring (late April 1993) under natural and above-normal precipitation regimes and in the fall (late October 1993) under natural precipitation. Unpassed seeds were also broadcast and drill-seeded into soil seedbeds at the same times. Microenvironmental factors and germination and plant establishment were monitored for 49 weeks in the spring experiment and 17 weeks in the fall experiment. For dungpat treatments, seedling emergence and survival were greater for unpassed than passed seeds in both precipitation regimes; however, sufficient numbers of seedlings established from passed seeds, and these plants had greater biomass and similar or greater seed production than plants from unpassed seeds. Slight changes in nutrients in dungpats and underlying soil indicated that partial decomposition and mineralization of dungpats had occurred by the end of the spring experiment. Both studies indicate that dungpat microenvironmental factors are greatly influenced by ambient moisture, temperature, and insolation, and by the nature of the underlying soil. These studies support the claim that plants established in dungpats could serve as nuclei of seed production for surrounding areas.

Crested wheatgrass (Agropyron cristatum [L.] Gaertn.) is one of the most commonly seeded exotic species in the western United States. Although many degraded Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) plant communities have been seeded with crested wheatgrass during rehabilitation efforts, seed banks of these communities have not been characterized. I sought to characterize and explain the variation among 33 seeded communities in the northeastern Great Basin. Hierarchical clustering and principal components analysis identified four possible seed bank categories in these communities. Seed bank categories varied from high to low crested wheatgrass dominance. The crested wheatgrass-dominated category is a particularly attractive setting to develop management strategies that reduce crested wheatgrass dominance and increase native plant diversity. It is also a common practice to seed crested wheatgrass in mixture with native species after a disturbance to increase diversity. Empirical estimates as to how the density of crested wheatgrass seed and seedlings interfere with native species establishment have not been defined. A greenhouse experiment was established using an addition series design to determine the influence of interference between crested wheatgrass and four important native species. The existence of seed bank categories of Wyoming big sagebrush communities seeded with crested wheatgrass agrees with the hypothesis that seed banks closely resemble floristic composition. In addition, these results support the hypothesis that seed bank composition has a strong influence on succession in these communities, and characterizing seed banks is necessary to develop ecologically based management strategies for seeded Wyoming big sagebrush communities. Interference from crested wheatgrass on many native species suggests that further management practices to enhance diversity in crested wheatgrass-dominated communities are necessary to reduce competition from crested wheatgrass in the seed bank as well as the aboveground vegetation. These results also suggest that the practice of simultaneously seeding native species with crested wheatgrass may likely result in poor native species persistence unless combined seed bank density and seeding rate of crested wheatgrass is sufficiently low.

A comparative index to digestible nutrients was established for Russian wildrye, crested wheatgrass, and intermediate wheatgrass seeded on foothill areas of Utah. The nutritive values of these grasses were compared by the lignin ratio method, the chlorophyllan ratio method, and the in vivo rumen bag process. Average digestion coefficients computed by the lignin ratio method for dry matter, ether extract, cellulose, and gross energy were highest for intermediate wheatgrass. Protein was more digestible for Russian wildrye. Digestible energy was adequate in all species to meet requirements for late lactation. Results from the chlorophyllan ratio method were excessively high and were not considered valid. Dry matter loss of Russian Wildrye was greater than losses from either of the wheatgrasses. Losses of dry matter due to 24-hour in vivo rumen fermentation and rinsing only of nylon bags were closely correlated.

Patterns of grazing on individual crested wheatgrass plants were studied using scale maps of plant basal outlines within randomly located plots. The occurrence and extent (part of plant grazed, stubble height) of grazing on each plant was recorded on the maps at two and three day intervals throughout a grazing treatment. Allometric equations for estimating phytomass from plant photosynthetic volume were generated using nonlinear regression analysis. Equations were specific to year. The percent weight remaining in the stubble of a grazed plant was estimated using a second-order polynomial equation relating cumulative percent plant height to cumulative percent plant weight. A modified bootstrap analysis was used due to the autocorrelated nature of these data. These equations were used to estimate the percent biomass grazed from individual plants. The presence of standing dead culms substantially reduced the severity of grazing on individual crested wheatgrass plants. This effect was most pronounced for large plants. The deterrence effect of xiii standing dead culms declined as plants matured, but remained an important factor affecting grazing severity. The pattern of grazing on crested wheatgrass plants was examined under three grazing systems: 1) continuous season-long grazing (CSLG), 2) high intensity grazing (approximately 60 percent utilization in eight days), and 3) short duration grazing. For all grazing treatments, a lower proportion of small plants was grazed than medium and large. Only under CSLG were small plants grazed more severely than large plants. Under all ocher grazing treatments, medium and large plants were grazed as severely as small plants. The proportion of plants regrazed was low when grazing began at the boot phenological stage and regrowth was minimal. It was higher when grazing began at later phenological stages , presumably due to the presence of regrowth. The proportion of small grazed plants that were regrazed was much lower than the proportion of large grazed plants that were regrazed. The re grazing event, however, involved, on average, more of the previously ungrazed portion of a plant than the part which had been grazed before. These results indicate that grazing of regrowth on crested wheatgrass pastures under CSLG may not be a serious problem.

Monitoring reproductive success, prey species composition, and colony size of marine birds has been proposed as a method of assessing changes in marine systems that are otherwise difficult to sample (Cairns 1987). I measured inter-annual and intra-seasonal variability in reproductive parameters, taxonomic composition of the diet, and adult body condition of Crested Auklets (Aethia cristatella) and Least Auklets (A. pusilla) at 2 colonies near the village of Savoonga, St. Lawrence Island, Alaska during the 2000-2002 breeding seasons to evaluate how reproductive success of planktivorous seabirds is related to diet. I also assessed the utility of two methods of population monitoring (surface counts and mark-resighting) for detecting annual changes in breeding populations of Crested and Least auklets during the 2001 and 2002 breeding seasons on the Kitnik colony. Average reproductive success was generally high (>60% of nests) for both auklet species during the 3 years of the study, but differed among years. Median hatching dates for both species were 2 weeks earlier in the year of highest reproductive success (2002), compared to the previous 2 years. In all 3 years, the diet of Crested Auklets was predominantly euphausiids, while the diet of Least Auklets consisted primarily of calanoid copepods, but species composition of the diet differed among years for both species. Crested and Least auklets consumed more of the large, lipid-rich copepod Neocalanus cristatus in 2002 than in the other 2 years of the study. The year of lowest reproductive success (2001) was associated with low prevalence of euphausiids in Crested Auklet diets late in the chick-rearing period and high prevalence of the small, low-lipid copepod Calanus marshallae in Least Auklet diets. I observed an increase in total body mass of Crested Auklets during the 2002 breeding season, whereas total body mass declined through the breeding season in the other 2 years. Seasonal changes in adult body mass of Crested Auklets may, therefore, be a useful indicator of food availability. Average body mass of Least Auklets declined in all 3 years, but was lowest in 2001, suggesting that low adult body mass of Least Auklets may reflect poor foraging conditions. Fat reserves of breeding auklets during egg-laying were not highly variable among or within breeding seasons and therefore were not a sensitive predictor of subsequent breeding success. Counts of Crested Auklets in plots on the colony surface were highest in areas of large average boulder size; Least Auklet surface counts were not as variable among plots. Maximum counts of both species of auklets in plots did not differ between years. Patterns of colony surface attendance during the breeding season, however, did differ between years. The colony surface attendance of both auklet species after hatching was higher in the year of high reproductive success. Preventing nest initiation by covering plots with tarps did not reduce subsequent colony surface attendance during chick-rearing (after the tarps were removed) for either species, suggesting that reproductive success, independent of differences in food availability, did not cause a difference in colony surface attendance. I estimated abundance of Least Auklets nesting in two 100-m�� plots using mark-resight methods. I concluded that surface counts may provide an indication of among-year differences in colony attendance, but underestimate the number of breeding individuals by a factor of 10. Mark-resighting techniques show more promise for detecting changes in the number of breeding pairs. Reproductive success, adult body mass, and post-hatch colony attendance of Crested and Least auklets appear positively associated with zooplankton availability, particularly the prevalence of N. cristatus in the diet. Annual monitoring of these 3 parameters, together with diet composition, are important for understanding how both natural and anthropogenic climate change may affect trophic structure of the northern Bering Sea ecosystem. / Graduation date: 2004

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