Steven S. Rosenstock

RELATIONSHIPS AMONG BREEDING BIRDS, HABITAT, AND RESIDENTIAL DEVELOPMENT IN GREATER TUCSON, ARIZONA

Bird abundance trends have been correlated with habitat changes in urban developed areas but have seldom been associated with specific patterns of urban-related habitat changes. We examined breeding bird-habitat relationships in 334 random plots ranging from undisturbed natural to highly developed land in Tucson, Arizona. In each plot we quantified 19 variables describing three land cover patterns (habitat physiognomy, flo- ristics, and spatial relationships of native habitat fragments) and correlated them with abundances of 21 bird species. Abundances of 17 bird species were associated with variables describing land cover pattern. In addition, we correlated abundance, species richness, and evenness for three bird guilds (non-natives, natives, and a native indicator guild) with land cover variables. Housing density best explained the variation in species richness for both the non-native (r2 = 0.79) and the indicator guilds (r2 = -0.69), whereas area of Upland Sonoran vegetative cover (r2 = 0.56) and distance from undisturbed washes (r2 = -0.56) correlated most strongly with the native-bird group. Finally, we developed and tested re- gression models predicting species richness for each bird guild. The following variables loaded into the predictive models: house density; percentage cover of paved areas; exotic, Upland Sonoran, and undisturbed riparian vegetation; and distance from undisturbed washes. The models explained 71% of the variation in non-native bird species richness, 56% of the variation in native bird species richness, and 60% of the variation in species richness for the indicator guild of birds. The correlations and regression models can be used to predict species richness responses to future residential development in the Tucson area.

Mechanisms of Thermoregulation and Water Balance in Desert Ungulates

Abstract Desert ungulates must contend with high solar radiation, high ambient temperatures, a lack of water and cover, unpredictable food resources, and the challenges these factors present for thermoregulation and water balance. To deal with the conflicting challenges of maintaining body temperature within acceptable limits and minimizing water loss, desert ungulates use a variety of physiological, morphological, and behavioral mechanisms. The mechanisms involved in thermoregulation and water balance have been studied in many domestic and wild African and Middle Eastern ungulates; studies involving ungulates inhabiting North American deserts are limited in comparison. Our objectives were to review available scientific literature on thermoregulation, water balance, and the effects of dehydration in desert ungulates. We discuss the physiological, morphological, and behavioral mechanisms used by ungulates to maintain temperature and water balance in arid environments, and the implications for research and management of desert ungulates in western North America.

Viewpoint: Benefits and impacts of wildlife water developments

Resource managers in the western United States have long assumed that water was a key limiting factor on wildlife populations in arid habitats. Beginning in the 1940s-1950s, state and federal resource management agencies initiated water development programs intended to benefit game species and other wildlife. At least 5,859 such developments have been built in 11 western states. Most state wildlife management agencies in the western United States have ongoing wildlife water development programs that vary greatly in extent. Ranchers and range managers also have developed water sources for livestock, many of which also are used by wildlife. Recently, critics have suggested that wildlife water developments have not yielded expected benefits, and may negatively impact wildlife by increasing predation, competition, and disease transmission. Based upon a comprehensive review of scientific literature, we conclude that wildlife water developments have likely benefitted many game and non-game species, but not all water development projects have yielded expected increases in animal distribution and abundance. Hypothesized negative impacts of water developments on wildlife are not supported by data and remain largely speculative. However, our understanding of both positive and negative effects of wildlife water developments is incomplete, because of design limitations of previous research. Long-term, experimental studies are needed to address unanswered questions concerning the efficacy and ecological effects of water developments. We also recommend that resource managers apply more rigorous planning criteria to new developments, and expand monitoring efforts associated with water development programs.

Developed Waters for Wildlife: Science, Perception, Values, and Controversy

Abstract Human-made or -modified water sources (i.e., catchments) are widely used for wildlife management in the arid western United States, where thousands of such catchments have been built to enhance wildlife populations and mitigate for the loss of natural water sources. For decades, the need for and value of catchments to wildlife was unquestioned. Recently, however, the use of catchments has become controversial, particularly on public lands. Impacts to wildlife populations and wildlife habitats have been central to the debate, which has, in large part, been fueled by a paucity of scientific information. Value-based conflicts over management practices on public lands also have played a significant role.

Wildlife Use of Water Catchments in Southwestern Arizona

Abstract Construction of water developments has been used as a wildlife-habitat improvement technique in desert environments since the 1940s. Use of water developments by wildlife has been described in anecdotal observations, through water-hole counts, and with triggered still-cameras, but few studies have directly quantified wildlife use. We used video surveillance equipment to document wildlife use of 3 water catchments located in the Sonoran Desert, southwestern Arizona, USA, from June 2000 to November 2003. For each visitation, we recorded time of day, season of use, and activities engaged in, and we correlated visits with temperature and relative humidity. We logged 37,989 observation hours and documented 34 species using the water catchments. Most of the species recorded visited water catchments year-round with use peaking during June and July. The number of visits by nongame species (i.e., bats, raptors, mammalian predators, and rodents) exceeded the number of visits by game species (mule deer [Odocoileus hemionus], doves [Zenaida spp.], and Gambels quail [Callipepla gambelii]). Visitation frequency for turkey vultures (Cathartes aura), owls, diurnal raptors, mule deer, coyotes (Canis latrans), and other mammalian predators increased with temperature. Most visits culminated in the animal drinking water. Other activities recorded were bathing, consumption of plant material and carrion, and intraspecies and interspecies interactions. We recorded 8 predation attempts: 4 by avian predators and 4 by bobcats (Lynx rufus). Although we documented that a number of species frequented water catchments, our observations do not prove need. However, we believe our observations do provide support for constructing water catchments that can accommodate a wide diversity of species.

Tassel-eared squirrel population, habitat condition, and dietary relationships in north-central Arizona

We examined the seasonal population dynamic of tassel-eared squirrels (Sciurus aberti) in north-central Arizona, USA, during 1996-1997 to assess relationships with forest structural habitat condition and dietary fungi use. Our 8 study sites averaged 66 ha and exhibited considerable variation in ponderosa pine (Pinus ponderosa) habitat structure. We conducted capture-recapture trapping during 3 seasons each year, for a total of 56,016 trap days and 2,542 captures of 450 squirrels. We attained population estimates with mean standard error ±10%. Density across periods ranged from 0.05 to 1.03 squirrels/ha, and fluctuated widely, at half our study sites, particularly between April and August trapping periods. Indices of recruitment averaged 0.14 juveniles/female. Survival rates averaged 0.78, with winter survival (0.63) significantly lower than other periods. We analyzed 382 fetal samples for seasonal hypogeous and epigeous fungi, of which 21 taxa were detected. Mean fecal fungal content was significantly higher in August (70.8% relative frequency) than in January (28.2%) and April (9.4%). Recruitment was strongly and positively related to both the number of interlocking canopy trees and August fungal content in fecal samples. August fecal fungal content was positively related to basal area for all tree species. Across all periods, squirrel density was positively related to fecal fungal diversity. Winter squirrel survival was inversely related to snow cover duration and positively related to dietary fungal diversity. Squirrel density fluctuations between April and August were positively tied to pine quadratic mean diameter. Forest management and restoration practices emphasizing intensive, widespread thinning may adversely impact tassel-eared squirrels and the fungi that provide food. Integrating squirrel habitat needs of interlocking canopies and other structural attributes in forest management will benefit squirrel populations.

Breeding bird responses to juniper woodland expansion.

In recent times, pinyon (Pinus spp.)-juniper (Juniperus spp.) woodlands have expanded into large portions of the Southwest historically occupied by grassland vegetation. From 1997‐1998, we studied responses of breeding birds to one-seed juniper ( J. monosperma) woodland expansion at 2 grassland study areas in northern Arizona. We sampled breeding birds in 3 successional stages along a grassland-woodland gradient: un-invaded grassland, grassland undergoing early stages of juniper establishment, and developing woodland. Species composition varied greatly among successional stages and was most different between endpoints of the gradient. Ground-nesting grassland species predominated in uninvaded grassland but declined dramatically as tree density increased. Tree- and cavity-nesting species increased with tree density and were most abundant in developing woodland. Restoration of juniper-invaded grasslands will benefit grasslandobligate birds and other wildlife.

Use of Wildlife Water Developments by Birds in Southwest Arizona During Migration

Abstract Anecdotal evidence suggests that desert water developments attract birds; however, few studies have focused on the role of surface water in habitat selection by migratory birds. Therefore, we studied bird use of wildlife water developments in the Sonoran Desert of southwestern Arizona, USA, using 2 observational approaches (bird surveys in washes with and without water developments and direct observations at water developments) and 1 experimental approach (direct observations at water sources with and without vegetation cover). In spring 2004, we conducted weekly bird surveys at 3 pairs (with and without water developments) of washes. In spring 2005, we designed an experiment to test whether migratory birds more frequently used water developments with than without vegetation cover. During spring, in both 2004 and 2005, we documented use of water by directly observing birds at 13 existing water developments. We found little evidence to support that water developments were important water sources for migratory birds. Migratory bird communities in desert washes near wildlife water developments did not differ in species richness, relative abundance, or density when compared with washes without water developments. This observation suggests that the wildlife water developments that we studied were not an attractant to migratory birds at the landscape scale. At a finer scale, migratory birds rarely (0.1% of all observations) used water developments and experimental water sources. However, resident bird species frequently were recorded (>69,000 observations) drinking and bathing at wildlife water developments. Based on our observations, we conclude that water developments are an important resource for local bird populations in the Sonoran Desert, USA, particularly during periods of drought.

A comparison of Landsat TM and MODIS vegetation indices for estimating forage phenology in desert bighorn sheep (Ovis canadensis nelsoni) habitat in the Sonoran Desert, USA

Sonoran Desert bighorn sheep (Ovis canadensis mexicana) occupy rugged upland areas that experience irregular periods of vegetation growth associated with precipitation events. These episodic and often spatially limited events provide important forage and preformed water resources that may be important drivers of animal movement and habitat use. Habitat-use models that incorporate forage phenology would broaden our understanding of desert bighorn ecology and have considerable potential to inform conservation efforts for the species. Field-based methods are of limited utility to characterize vegetation phenology across large areas. Vegetation indices (VI) derived from satellite imagery are a viable alternative, but may be confounded by areas of high relief and shadow effects that can degrade VI values. The varying spatial and temporal resolutions of readily available satellite sensors, such as the Landsat thematic mapper (TM) and moderate-resolution imaging spectrometer (MODIS), present additional challenges. In this study, we sought to minimize degrading effects of terrain on TM- and MODIS-based estimates of vegetation phenology. We compared effects of high topographic relief on time series MODIS- and TM-based VI such as the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) using VI departures from average (DA) in shaded and unshaded areas. Sun elevation angle negatively impacted TM-derived NDVI and EVI values in areas of steep terrain. In contrast, MODIS-derived NDVI values were insensitive to sun elevation and terrain effects, whereas MODIS-derived EVI was degraded in areas of steep terrain. Time series MODIS NDVI and EVI DA values differed significantly during months of low sun elevation angle. Average MODIS EVI departure values were ≥20% lower than NDVI under these conditions, confounding time series estimates of plant phenology. Our best results were obtained from MODIS 16-day composited NDVI. These remote-sensing-based VI estimates of seasonal plant phenology and productivity can be used to inform models of habitat use and movements of desert bighorn over large areas.

Quality of Water Available to Wildlife in Desert Environments: Comparisons Among Anthropogenic and Natural Sources

Abstract We compared water quality at natural tinajas and 2 types of wildlife water developments in the deserts of southeastern California, USA. We analyzed water samples collected from each site for pH, conductivity, alkalinity, aluminum, ammonium, arsenic, cadmium, calcium (Ca), chloride, chromium, copper (Cu), iron, lead (Pb), manganese, magnesium (Mg), mercury, nickel, nitrate, organophosphate, potassium, silica, silver, sodium, sulfate, and zinc (Zn). With few exceptions, values for pH were within standards established for livestock drinking water. The levels of Ca, Cu, Pb, Mg, silica, and Zn differed by type of water source. We believe those differences are related to construction materials, design, or substrate. With the exception of pH, none of the analytes tested for exceeded standards recommended for livestock drinking water. We conclude that the quality of water available at man-made water sources in southeastern California desert environments does not constitute a wildlife health threat.