During the period of October to April of the winter of 1950-51, an ecological study was undertaken of a population or passerine birds wintering in a segment of the Utah Lake Shore. Available winter weather data indicated that although such factors as precipitation, temperature, and wind may often be severe, they are not critical enough to prevent a fairly large population of passerine birds from spending the winter months in the study locale. Five fairly distinct plant communities can be recognized in the area. There is evidence which indicates that certain passerine bird species are especially dependent on a particular type or types of vegetation. The plant communities produce ample amounts of food to meet the requirements of wintering birds. It was found that nine passerine species play an important part in the natural economy of this area in winter. Such species as the song sparrow and marsh wren are relatively stable in their numbers and occurrence, and have number per hour ratings which are significant. Other birds, among them the redwing and crow occur here in great numbers but fluctuate widely in day by day totals. Their number per hour ratings are comparatively meaningless as an index to relative numbers, but are significant in that they indicate different modes of habit of these birds. The thesis is intended to be a contribution to our knowledge of the wintering habits of perching birds in lakeside areas or central Utah.

Research was conducted to determine the effect of prey numbers on the nesting success of the Ferruginous Hawk (Buteo regalis). Conditions associated with nest site selection were also established. Frequent visits were made to active nests to determine clutch sizes, hatching dates and fledging success. Prey remains were collected from nests and analyzed. Kilometer square transects were made throughout the study area in 1974 to determine jackrabbit densities. A drastic decline in numbers of Ferruginous Hawks occurred. The number of young fledged also declined throughout the study while nestling mortality increased. Jackrabbit numbers were high in 1972 and then declined prior to the spring of 1973. The decline in hawk numbers appeared to be directly correlated with the reduction in prey densities. No directional trend was evident in nest exposure. Shade was not an apparent requirement in nest site selection. Tree nests tended to be in isolated trees that were taller than those surrounding them.

This study attempts to give a preliminary survey of the marsh habitat in Powell's Slough near Utah Lake. The following aspects are treated: seasonal waterfowl utilization of the slough, productivity of nesting water-fowl, description of the vegetation, invertebrate analysis, and analysis of environmental factors that may influence the habitat.

Three desert Artemisia tridentata communities in Rush Valley, Utah were trapped for small rodents during the summer of 1970 in a mark-recapture study. Population densities were estimated using several indices for each population category. Animals were weighed and rodent biomass calculated for each species throughout the summer. Populations, biomass, and other data were then analyzed to gain a better understanding of A. tridentata community types of the Great Basin. Peromyscus maniculatus, Eutamias minimus, and Reithrodontomys megalotis were common to area 1. Peromyscus maniculatus, E. minimus, and Perognathus parvus were common to areas 2 and 3. The peak estimated standing crops were 182.8, 143.1, and 129.7 g/acre for areas 2, 1, and 3 respectively. The population and biomass of area 2 peaked in mid-summer, area 1 in early summer, and area 3 in late summer. Results from a similar study indicate mountain A. tridentata communities may be less productive, in terms of rodent biomass, than desert A. tridentata communities at lower elevations.

Approximately 475 acres of aspen, oak brush, and grass-forb-shrub communities were treated with herbicides. The populations of arthropods, birds, and mammals were investigated on treated and untreated areas and the results were compared. There was no difference between soil arthropod populations on treated and untreated aspen plots but a significant increase in these populations on treated meadow plots. The foliage insect populations were significantly lower on the treated aspen plots but were significantly higher on the treated meadow plots. The aquatic invertebrates were not affected by the treatments. Bird populations ware lower in the treated area during the nesting season (June), higher in the treated area during July and August and nearly the same in each area during September. Small mammal populations decreased significantly on the treated meadow plots. Microtus populations increased while all other small mammals decreased in numbers on treated aspen plots. Use of the treated areas by mule deer was significantly reduced, while use of the same areas by elk was slightly increased.

A study was made of the ecology and floristics of a small bog lake referred to as Moss Lake, in the Grandaddy lakes region of the Uinta Mountains , Utah . Three consecutive summers, 1948, 1949, and 1950, were spent in collecting the data presented in this study. Throughout the study the following ecological measurements were made: 1. Water 2. Soil 3. Macroscopic vegetation 4. Plankton 5. Macroscopic animal forms.

Microfungi were isolated from soil samples by the soil plate method. Soil samples were collected at depths of 0-1", 1-4", and 4-8" both between and beneath the canopy of the dominant vegetation in stands of greasewood, sagebrush, and pinyon-juniper. Salinity, pH, and percent organic matter were measured for each soil sample. A total of 148 strains of fungi representing 141 species and 46 genera were isolated and identified from these alkaline soils, Few strains, including some Aspergilli, occurred only in the more saline greasewood soils, while many strains, including several Penicillia, occurred in both sagebrush and piny-on-juniper soils but were lacking in the greasewood soils. Many strains, including Penicillia, were found primarily in the more organic soils beneath plants, while few strains, including some Aspergilli, were found primarily in soils from between plant cover. Strains of the family Demataceae were found primarily in the surface layers. There was no noticeable difference in the kinds of fungi isolated from the 1-4" and 4-8" layers.

The present work is a general survey of the vegetation of the Utah portion of the Dinosaur National Monument with special emphasis on some of the ecological aspects of the area. The vegetation ranges from xerophytic plant communities of the lower elevations to mesophytic communities of the higher elevations. Hydrophytic plant communities are also present to a limited extent along the Green River and where seeps or springs arise. Soils vary from fine clay to coarse gravel. The dividing lines between formations is often marked by extreme differences in soil type. During the author's first collecting trip into the Monument in April 1955 the possibility of correlations between geological formations and vegetation was suggested by the occurrence of certain plant species on some of the formations. The presence of a well defined geological section in a relatively short distance makes it possible to determine if such correlations exist.