I designed and tested experimental enclosures with 1-way exits for the study of emigration in house mice. Rapid emigration from barren enclosures supported the contention that all mice can find and use the exits if conditions in the enclosures are unsuitable for them. Invariable residency in resource-rich enclosures during the spring, summer and fall revealed that resident animals will not cross the exits during routine behaviors. The enclosures and exits permitted normal emigratory and residency behavior. In experiments on the role of emigration in population regulation, the number of resident mice was consistent in enclosures with fixed levels of resources. The number of residents was about double in enclosures with twice the resources. The first male and few females added in each trial usually became resident, and mice added subsequently usually emigrated. My data suggest that mice were regulating their numbers to available resources through spacing and emigration.

Management strategies are needed to reduce the rate at which brown-headed cowbirds (Molothrus ater) parasitize their hosts. I investigated whether vegetation management could be used to reduce parasitism by seeking differences in nest-site microhabitats of hosts in a riparian area of central Arizona. During 1993 and 1994, I quantified vegetation characteristics in 0.04 ha plots centered on 128 nests of 4 commonly parasitized species and 4 infrequently parasitized species. I compared characteristics between (1) parasitized and unparasitized nests of common hosts, and (2) nests of common and infrequent hosts. Factors associated with outcome of parasitism were vegetation volume at nest, size of nest substrate, distance from nest to visual obstruction below nest, and presence of large trees near the nest. Whether nests belonged to common hosts or infrequent hosts was best predicted by nest height. My results indicate riparian areas should be managed for large trees and numerous shrubs when the goal is to reduce parasitism.

Whitebark pine (Pinus albicaulis Engelm.) tree-ring chronologies of 700 to greater than 1,000 years in length were developed for four sites in the Sawtooth-Salmon River region, central Idaho. These ring-width chronologies are used to (1) assess the dendrochronological characteristics of this species, (2) detect annual mortality dates of whitebark pine attributed to a widespread mountain pine beetle (Dendroctonus ponderosae Hopk.) epidemic during the 1909 to 1940 period, and (3) establish the response of whitebark pine tree ring-width growth to climate variables. Crossdating of whitebark pine tree-ring width patterns was verified. Ring-width indices had low mean sensitivity (0.123-0.174) typical of high elevation conifers in western North America, and variable first order autocorrelation (0.206-0.551). Mortality of dominant whitebark pine caused by mountain pine beetle had a maxima at 1930 on all four sites. Response functions and correlation analyses with state divisional weather records indicate that above average radial growth is positively correlated with winter and spring precipitation and inversely correlated with April temperature. These correlations appear to be a response to seasonal snowpack. Whitebark pine is a promising species for dendroclimatic studies.

Determination of reproductive success in birds is important for understanding population dynamics, habitat quality, and features necessary for breeding. I incorporated behavioral observations, nest monitoring, and a reproductive ranking index (Vickery et al. 1992) to (1) categorize painted redstarts (Myioborus pictus), solitary vireos (Vireo solitarus plumbeus), and western wood-pewees (Contopus sordidulus) as breeders or nonbreeders, (2) locate nests, (3) monitor nest status, and (4) determine nest success and parasitism rates in 14 canyons of the Huachuca and Santa Rita mountains, Arizona during 1994-1995. I built logistic regression models for each species that correctly classified 58-68% of successful nesters from unsuccessful nesters, 62-85% of areas used by birds from random sites along the canyons, and at each nest, I correctly classified 39-60% of successful nest sites from unsuccessful nest sites and 87-95% of nest sites from nonoverlapping sites in areas of use. These models can be used to determine areas that would promote occupancy and successful nesting by these 3 species.

Geographic range and numbers of buff-breasted flycatchers (Empidonax fulvifrons) have decreased in Arizona. I conducted surveys to locate additional populations. Results suggested that some small populations have disappeared since 1980, but that other small populations have increased. I estimated reproductive success using an index based on adults' behavior. I measured vegetation in used areas, nest sites, and available areas. I used logistic regression to compare used to available areas and nest sites to used areas. Used vs. available comparisons indicated that buff-breasted flycatchers used areas dominated by pines, with a sparse oak understory. I found significant associations between buff-breasted flycatcher presence and vegetation type, structural stage, canopy cover, and forest patch width. I developed a habitat model to help manage this rare species. I recommend continued monitoring of buff-breasted flycatcher populations and creation of open pine forest with an open understory of oak. Fire may facilitate development of potential habitat.

With Anglo settlement of southern Arizona in the late 1800s, fire regimes were altered dramatically. Currently, desert scrub has experienced a dramatic rise in frequency and size of wildfire which may remove fire-intolerant perennials that define the community structure. On the contrary, woodlands and forests now contain excessive fuel build up and require prescribed burning to restore the system's balance. These opposing attitudes reflect the conundrum of how to manage naturally occurring fires, or where and when to initiate prescribed burning to recreate each vegetation community's "natural" fire regime. To resolve this dilemma, there is need to discern natural fire histories by collecting specific baseline data such as where, when and how the landscape has burned. This research has been focused on the design and development of a relational database, and the incorporation of a geographic information system to develop a system that can be used to fulfill this need.

Little is known about habitat selection by elf owls (Micrathene whitneyi) and western screech-owls (Otus kennicottii). From 1994 to 1996 in the Sonoran Desert, I used point counts and nest searches to examine habitat selection by both species at multiple spatial scales. The abundance of both species had a positive association with percent cover of washes and mesquite (Prosopis spp.) at the scale of the study area. At both the scale of the study area and the nesting area, elf owls selected areas with high densities of mature saguaros (Carnegiea gigantea) and saguaro cavities. Elf owls nested only in woodpecker cavities in saguaros, whereas western screech-owls nested in both saguaro cavities and in natural cavities in mesquite. Western screech-owls nested nearly exclusively in gilded flicker (Colaptes chrysoides) cavities when they nested in saguaros. Patterns of nest cavity selection by elf owls suggest they may choose cavities that provide thermoregulatory advantages. I give management recommendations based on my findings.

I studied bat use of 3 isolated water developments on the Cabeza Prieta National Wildlife Refuge in southwestern Arizona between May 1995 and August 1997. I recorded bat echolocation calls to measure overall activity, videotaped bat behavior and identified aquatic insects to determine whether bats were feeding or drinking, mist netted to assess visitation patterns with respect to season, sex, and reproductive condition for each of 4 species captured, studied movements of banded individuals, and monitored roosts of the California leaf-nosed bat (Macrotus californicus) in nearby mines. Echolocation activity was much higher at water than in nearby dry desert washes and was greater in dry washes than at random sites away from water. Bats visited water in all seasons, visiting primarily to drink, not to feed on insects. The California leaf-nosed bat constituted 41% of more than 1,000 captures. I concluded that in my study area this species made extensive use of water developments for drinking, particularly during lactation.

On the Colorado Plateau, environments occupied by Mexican spotted owls (Strix occidentalis lucida) receive intense levels of recreational activity that could adversely effect their behavior and reproductive success. Any spatial restrictions on recreational activities in these narrow canyons would likely eliminate all recreational activity within a given canyon. We assessed changes to activity budgets and nest attendance caused by hikers (Chapter 1) and examined factors that influenced flush responses of roosting owls to hikers (Chapter 2). We conclude that high levels of recreational activity in nesting habitat may be detrimental to Mexican spotted owls and recommend a 205-m radius buffer zone around occupied nests. Based on responses of roosting owls to hikers, we established response thresholds as a basis for exploring management options that will maximize protection of owls and minimize restrictions to recreationists.

The effects of fire on vegetation in the upper encinal woodlands, Santa Catalina Mountains, southeastern Arizona, were studied following a wildfire in July 1995. Similar unburned and burned sites were compared to determine differences (alpha = .05) for frequency, density, and percent cover of herbs, shrubs, and trees through observations made during early June of 1997 and 1998 (two and three years postfire). For herbs, which showed their opportunistic characters, differences existed for frequency and percent cover each year and density in the third year. For shrubs, due to the ability of the dominant species, Arctostaphylos pungens (pointleaf manzanita), to rapidly reseed itself, no differences existed for frequency or density each year; but total mortality of mature A. pungens resulted in differences for percent cover each year. For trees, due to the ability of Quercus spp. to vigorously stump sprout, no differences existed for frequency, density, or percent cover each year.