I surveyed songbirds and lizards adjacent to dry rivers throughout metropolitan Tucson and related species richness to recreational use and habitat using stepwise multiple regression. Habitat characteristics included vegetation structure and floristics in river-edge areas, adjacent land uses, and land uses of the surrounding landscape. Bank stabilization had a negative effect on species richness of all bird groups. Total vegetation cover, mesquite (Prosopis velutina) density, and natural open space had a positive effect on species richness of most bird groups. Tall vegetation was important for species richness of lizards. River corridors could function as conservation corridors for five bird species and two lizard species. However, habitat for many other species was not continuous across the metropolitan area. Recommendations include protecting mesquite bosques without bank stabilization, protecting wide areas of upland vegetation near large protected areas, and increasing structural diversity and use of native plants in river parkways.

I determined if Sonoran pronghorn (Antilocapra americana sonoriensis) could meet water and mineral requirements through consumption of forage. I sampled vegetation using dry weight rank and comparative yield methods in southwestern Arizona from June 1995 to May 1996 to determine preformed water, nutrient content, mineral content, and vegetation abundance. Water and nutrient content of plants varied between 2 sites and among 5 seasons (P ≤ 0.05). Plants consumed by pronghorn were higher in moisture and nutrients (P ≤ 0.05) than non-forage species. I constructed a model for Sonoran pronghorn diet based on field data. I used the model to describe dietary intake. Water intake predicted by diet models ranged from 1.1 to 6.1 L/animal/day; often exceeding predicted total water requirements (1.8-3.4 L/animal/day). Models predicted that forage provided adequate water for pronghorn during 5 seasons at 1 of 2 study sites and deficiencies for 5 of 11 minerals at both study sites.

I compared vegetation features and rodent communities between manipulated and non-manipulated ranges in southeastern Arizona during summers 1996 and 1997. I also examined the effect of burying traps to determine if this procedure altered trap sensitivity. I used two-way analysis of variance or paired t-tests for all comparisons and identified relationships between rodents and vegetation features with linear regression. There was no difference (P ) in rodent species richness or population size between mechanically treated and reference areas. Rodent species richness and population size were greater on ungrazed compared to grazed areas (P ), but there was no difference in rodent diversity (P = 0.13). Prescribed fire did not have an obvious impact on rodent species richness or population size, though there seemed to be an increase in kangaroo rats following the burn. Buried traps may have demonstrated a reduction in sensitivity because I caught fewer animals in those traps compared to non-buried traps (P = 0.087).

Historically, wildfires in mixed conifer forests of Southwestern sky islands were frequent events. Dendrochronological methods were used to reconstruct fire regimes and stand age structures in the Huachuca Mountains of Southeastern Arizona. Pre-settlement (i.e., before ca. 1870) fire intervals ranged from 4 to 10 years, with many fires spreading over the entire sample area. Stand age distributions show an increase in more shade-tolerant tree species. Although ponderosa pine is still the dominant overstory tree species, recent recruitment is predominantly southwestern white pine and Douglas-fir. Establishment of Ft. Huachuca in 1877 was a precursor to extensive use of timber, mineral, range and water resources in the Huachuca Mountains. The fire regime was altered at this time, with only one subsequent widespread surface fire recorded in 1899. Settlement era land-use practices may be responsible for changes in stand structure and composition.

Masked bobwhites used sites with more structural diversity than what was available on the Buenos Aires National Wildlife Refuge during 1994-96. Selected habitat variables that adequately predicted habitat use by masked bobwhites included percent herbaceous canopy cover, structure at 15 cm and 2 m, forb richness, and season. Masked bobwhite used more structural diversity than Gambel's and scaled quail. Gambel's quail had broader habitat tolerances than either masked bobwhite or scaled quail. Selected habitat variables that revealed differences among masked bobwhites, Gambel's quail, and scaled quail included percent woody canopy cover, structure at 15 cm, forb richness, and season. A historic perspective revealed that masked bobwhites used sacaton grasses that grew along the floodplains as important escape cover. I believe that we need to restore the integrity of the grassland ecosystems including the floodplain if we are to recover masked bobwhite quail.

The National Gap Analysis Program (GAP) is currently developing geographic themes in a Geographic Information System format for statewide analyses of biodiversity issues. This study uses several of the Arizona GAP themes to demonstrate how they might be utilized in resources planning. By overlaying the Arizona GAP vertebrate themes, species richness maps were created. The species richness maps were intersected with the Arizona GAP landcover and land management layers to analyze how the richness areas are distributed across the landscape. Areas of high species richness were then analyzed for how well they are represented within existing conservation areas. The development of vertebrate distribution models is also discussed, since their accuracy greatly influences the species richness maps development.

I examined trends in relative abundance and species richness of breeding and wintering grassland birds before (1996) and after (1997, 1998) a spring prescribed burn in a mesquite-dominated desert grassland at Buenos Aires National Wildlife Refuge, Arizona. The burn was moderate in intensity, patchy in extent, and affected ground cover more strongly than shrub cover, smaller shrubs more strongly than larger shrubs, and killed 1% of velvet mesquite (Prosopis velutina). Species richness of breeding birds decreased in the first year post-burn. Of breeding species, black-throated sparrows (Amphispiza bilineata) and mourning doves (Zenaida macroura) increased; whereas Botteri's sparrows (Aimophila botterii), Cassin's sparrows (Aimophila cassinii), and pyrrhuloxias (Cardinalus sinuatus) decreased in relative abundance. Breeding species characterized as not shrub-dependent exhibited changes that were more pronounced than those for shrub-dependent species. Of wintering birds, ladder-backed woodpeckers (Picoides scalaris) and vesper sparrows (Pooecetes gramineus) increased, and cactus wrens (Campylorhynchus brunneicapillus) decreased in relative abundance.

I determined density and habitat use of desert mule deer (Odocoileus hemionus crooki) on the Buenos Aires National Wildlife Refuge, a semidesert grassland in southeastern Arizona, in 1996. I observed 219 groups of deer; densities varied from 0.9 ± 0.3 (SE) deer/km² in summer to 2.5 ± 1.3 in winter. Herd size varied from 1.5 ± 0.1 deer/group in summer to 9.7 ± 2.0 in winter. Density of females was greater than males (0.9 ± 0.3 and 0.03 ± 0.04, respectively). Mule deer used subshrub-grass more in summer (χ² = 54.8, 6 df, P < 0.0001) and Russian thistle (Sallsola kali) less and cactus more in autumn (χ² = 60.2, 6 df, P < 0.0001) than expected. Deer used mesquite (Prosopis velutina) less than expected, which may have been due to the difficulty of observing deer in dense cover. In general, the mule deer population was widespread, had a high proportion of females, and used vegetation associations as available.

<p> The state and federally endangered California clapper rail (<i> Rallus longirostris obsoletus</i>) has declined in abundance and been reduced in range and now occupies fragmented intertidal saltmarsh only within San Francisco Bay. Historically extensive salt marsh habitats existed in San Francisco Bay and today, remnants are largely restricted to the water's edge with dikes and levees separating marshland from modified habitats unsuitable for clapper rails. Clapper rail population abundance has roughly tracked a series of positive and negative impacts including market hunting at the turn of the 20th century, widespread habitat reduction and fragmentation, and invasive species introduction and eradication programs. Despite these changes, rail populations have been subject to the ebb and flow of the tides, which regularly inundate salt marsh habitats. The influence that tides have on vertebrate species living in intertidal saltmarsh should be substantial, but the relationship between tide and California clapper rails is poorly understood. This research identified important ways in which tides influenced demographic processes, space use, and resource selection in California clapper rails. Tidal inundation in San Francisco Bay saltmarshes creates zonation in plant communities, typically with tall monocots in the low marsh (<i>Spartina </i> sp.), short pickleweed (<i>Sarcocornia pacifica</i>) in mid-elevation ranges, and gumplant (<i>Grindela humilis</i>) in the high marsh. Invasive Spartina (<i>Spartina foliosa x alterniflora </i>) grows taller and thicker than native Pacific cordgrass (<i> Spartina foliosa</i>). Invasive Spartina also grows lower onto mudflats, further up into pickleweed areas, and provided both nesting habitat and tidal refuge for clapper rails. In Chapter 1, I examined survival rates of California clapper rails. Specifically, I investigated whether seasonal patterns observed in the early 1990s were still evident and assessed the influence that Invasive Spartina and the degree of tidal inundation on weekly survival rates in four South San Francisco Bay salt marshes. Between January 2007 and March 2010, California clapper rail annual survival was 73% greater in Spartina-dominated marshes (&Scirc; = 0.482) than in a control marsh dominated by native vegetation (&Scirc; = 0.278). Lower survival also occurred during periods when tide height was greatest and during the winter. Survival patterns were consistent with Invasive Spartina providing increased refuge cover from predators during tidal extremes which flood native vegetation, particularly during the winter when the vegetation senesces. Tide heights also strongly influenced selection for artificial habitats provided adjacent to one marsh during the winters of 2010-2011 and 2011-2012. Ten floating islands equipped with canopies providing cover were monitored using time-lapse cameras for evidence of clapper rail use. Clapper rails regularly used artificial islands once tides reached heights equal to the average surface elevation of the marsh. When tides had inundated the marsh plan, observed use of the artificial islands was more than 300 times expected use based on the surface area provided. Probability of use varied among the islands and low levels of use were observed at night. Endemic saltmarsh species are increasingly at risk from habitat change resulting from sea-level rise and development of adjacent uplands. Escape cover during tidal inundation may therefore need to be supplemented if species are to survive. I developed a new method to estimate space use accounting for individual movement phases within non-stationary relocation datasets using simulated radio-telemetry data. To define movement phases I used a nonparametric, multivariate test to detect change points in the mean or variance of a sequence of x,y coordinates. Once all phases (change points) were identified, Gaussian kernel density analysis was used to estimate space use during each phase, which I termed change-point utilization distributions (CPUDs). One advantage of this technique is that the location of change points can subsequently be tested for relationships with conditions that might trigger a change in how individuals use space. Change points in clapper rail movement were associated with a variety of environmental and biotic variables including high tides, nesting activity, intrusion by neighboring clapper rails, and transient movements outside the home range. Change points occurred more than twice as frequently during the highest observed tides relative to all other tide heights. Another use of CPUDs is that space use patterns of adjacent individuals can be evaluated for joint overlap only during specific time periods when overlap occurs. I used CPUDs developed for California clapper rails and identified the point within overlapping space-use estimates where each individual had priority access to the resources within its utilization distribution (i.e. the lowest kernel density isopleth that was common to two overlapping individuals). This provided an estimate of the spatial region at which individuals exhibited territoriality. During the breeding season, space use distributions overlapped less and average territory size increased relative to the non-breeding seasons. Population density implied by these territory sizes (1.38 birds/ha) is comparable to density estimates during the 1970s and 1980s. Together these findings show the great degree to which clapper rail behavior and demography can be influenced by the tides that populations experience. It is my hope that conservation efforts for this species, particularly in the arena of habitat restoration may benefit from this research.</p>

Land use is the major global driver of biodiversity loss and ecosystem change. In this thesis the impact of an important land use practice, livestock grazing, in the population dynamics of a keystone species of temperate grassland ecosystems, the field vole Microtus agrestis, was investigated in a manipulative grazing experiment in the UK uplands. Vole densities at different spatial scales declined with increasing grazing intensities. This decline was especially acute and non-linear at high altitudes, where the preferred habitat of voles is less abundant. The activity of an important vole predator, the red fox Vulpes vulpes, declined accordingly. The evidence suggested that the availability of voles to foxes changed between grazing treatments. A behavioural response to reduced habitat quality was the most likely mechanism to explain vole declines with grazing, while food limitation or increased predation received no support as valid mechanisms to explain vole declines. Grazing increased vole mobility, changed sex-specific patterns of natal dispersal, affected the age structure of the female population and led to biases in sex ratios amongst the adult population. Despite profound demographic changes, the dynamics of the vole population was unaffected by grazing. Neither direct nor delayed density dependent dynamics nor seasonal dynamics changed between grazing treatments. Apparent survival in adults was not direct density dependent and similar in ungrazed and grazed areas. Negative direct density dependence in reproductive and immigration rates, and population growth rates at different spatial scales was strong and did not change in response to grazing. Thus, livestock grazing reduced vole densities probably through a behavioural response to grazing, but it did not affect the demographic mechanisms of population regulation or vole population dynamics.