James P. Ward

Bio: James P. Ward is an academic researcher from United States Department of Agriculture. The author has contributed to research in topics: Threatened species & Northern spotted owl. The author has an hindex of 4, co-authored 5 publications receiving 161 citations. Previous affiliations of James P. Ward include New Mexico State University & Humboldt State University.

Habitat selection by northern spotted owls : The consequences of prey selection and distribution

Abstract: We tested three predictions of a hypothesis that states Northern Spotted Owls (Strix occidentalis caurina) select habitat according to the distribution of their primary prey. Our predictions were that Northern Spotted Owls should (1) select larger (> 100 g) species among the assemblage of available prey, (2) select habitats according to the distribution of large prey, and (3) the owl's reproductive success should be influenced by the availability of large prey. We also evaluated the potential energetic value of several prey species. We found that Northern Spotted Owls (n = 11 pairs and 1 single male) in northwestern California differentially selected the dusky-footed woodrat (Neotoma fuscipes), a moderately large sigmodontine rodent (x mass = 232 g). When foraging, owls selected late seral forest edge sites where dusky-footed woodrats were more abundant. Although the relationship between site selection, prey abundance, and the owl's breeding success was not statistically significant, the average abundance of dusky-footed woodrats at sites foraged by breeding owls (x = 11.4 woodrats 100-trap-nights -1 ) was greater than at sites foraged by nonbreeding owls (x = 4.7 woodrats 100-trap-nights -1 ). We estimated that a male Spotted Owl would require 150,015 to 336,232 kJ over a 153-day period while helping to produce one young, and concluded that the selection of woodrats provided a potential energetic benefit over the use of other prey. These findings provide a partial explanation for the owl's affinity for late seral forests.

Density of northern spotted owls in northwest California

Abstract: We estimated densities of northern spotted owls (Strix occidentalis caurina) over 4 years using intensive surveys of marked individuals on a 292-km2 study area in northwest California. For the 4-year sampling period, estimates from empirical and Jolly-Seber methods were in close agreement, yielding a crude density of 0.235 owls/km2 (95% CI = 0.214-0.256) and ecological densities of 0.544 (95% CI = 0.495-0.592) and 0.660 (95% CI = 0.601-0.719) owls/km2 of suitable habitat, using 2 definitions of suitable habitat. Increases in density over the 4 years were attributed to population processes, such as immigration, rather than internal increases within the sampled area. Densities in our area were relatively high when compared with other populations. Our study design should be useful for making geographic and habitat comparisons and for monitoring spotted owl populations. Estimates from our study and the U.S. Forest Service indicate a 60.0-82.5% reduction of current spotted owl populations on at least 1 National Forest under current management plans by the U.S. Forest Service. J. WILDL. MANAGE. 54(1):1-10 Over the past decade, the northern spotted owl has become the focus of controversial management policies in the Pacific Northwest because of the intimate association of the spotted owl with old-growth coniferous forests (Forsman et al. 1984, Gutierrez and Carey 1985, Dawson et al. 1987, Simberloff 1987, Thomas et al. 1988). Thus, an important element in their management will be estimating and monitoring changes in abundance of spotted owls (Dawson et al. 1987). Animal abundance can be measured as the number of individuals in the population (population size), the number of individuals per unit area (absolute density), or the density of 1 population relative to another (relative density) (Caughley 1977:12). Absolute density can be further subdivided into crude density-measured with respect to all of the area containing the population, and ecological density-measured with respect to a particular habitat (Johnson 1978:11, Tanner 1978:2). Absolute density is necessary for determining population and trophic dynamics (Verner 1985) and effective population sizes of demes (Barrowclough and Coats 1985). Relative density has been used to make comparisons between spotted owl populations and habitats (Forsman et al. 1977, Garcia 1979, Marcot and Gardetto 1980). However, these measures require standardization by some measure of absolute density (Caughley 1977:14, Verner 1985) and similar detection probabilities of individuals (Andersen et al. 1985) to ensure that relative measures provide an accurate index of abundance. Therefore, absolute density provides an initial step in estimating abundance. In this paper, we report empirical and markrecapture estimates of absolute density of northern spotted owls in northwestern California from 1985 through 1988. Our objectives were to estimate absolute density of northern spotted owls, to provide general guidelines for estimating density of northern spotted owls, and to evaluate our estimates in relation to current management plans. Our study would not have been possible without the field assistance of K. E. Young, C. A. Moen, J. A. Blakesley, T. J. Evans, and M. B. Kasper. C. A. Moen and J. A. Blakesley also assisted in data compilation. We would like to thank D. M. Solis, J. Kahl, D. Kudrna, J. L. Mattison, L. Roberts, A. C. Chrisney, M. Fox, and M. Smith of the Six Rivers National Forest for their help in providing information during this study. R. Rhino provided transportation. G. F. Barrowclough, J. A. Blakesley, J. A. Crawford, E. D. Forsman, W. S. LaHaye, J. D. Nichols, B. R. Noon, D. M. Solis, N. G. Tighlman, and J. Verner reviewed earlier drafts of this manuscript. Funding was provided by California Department of Fish and Game, Federal Aid

Influence of Habitat Characteristics on Detected Site Occupancy of the New Mexico Endemic Sacramento Mountains Salamander, Aneides Hardii

Abstract: The Sacramento Mountains Salamander (Aneides hardii) is a state-listed threatened species endemic to three mountain ranges in south-central New Mexico. Information about the ecological requirements of this species is inadequate for managers to make informed conservation decisions, yet changes in management practices are needed throughout the species range because of poor forest health. During summer 2004, we examined patterns of A. hardii distribution in relation to several abiotic and biotic parameters on 36 plots, each of which was 9.6-ha in area and located in mixed conifer forest. We evaluated 18 a priori logistic regression models using Akaike's Information Criterion corrected for small-sample bias (AICc). The model with the highest ranking (lowest AICc value) included soil moisture and soil temperature, and the second highest ranked model (DAICc 5 0.05) included only soil temperature. Soil temperature was lower, and soil moisture was higher on plots where salamanders were detected. The relative importance of canopy cover and log volume was low in this study likely because the study plots, all of which had sufficient canopy cover and log volume, had similar disturbance history. We recommend managers focus on practices that ensure salamander microhabitats remain cool and moist in conservation areas. Resource managers are challenged with bal- ancing human interests and the conservation of threatened and endangered species. This is a current issue in the western United States because of the need to manage forests for catastrophic fire prevention while considering the response of sensitive forest species to silvicultural practices. Fire suppression has

Using Search Time and Regression to Estimate Abundance of Territorial Spotted Owls.

Abstract: Using conventional sampling methods, unbiased, precise estimates of the number of individuals in a population can be difficult to obtain for rare, secretive species. We used a Leslie regression model (LRM) to estimate the number (No) and the variance of the number (V(No)) of adult and subadult Northern Spotted Owls in a territorial pop- ulation from direct counts within a 292 km2 study area. Estimates of No from day counts were more accurate and precise and more robust to fluctuations in survey effort than estimates from night counts. LRM estimates from day counts were not significantly different from two different maximum-likelihood estimates and required 30-64% less effort. These findings suggest a less costly method for statistically comparing Spotted Owl abundance between spatial or temporal units.

Science verses political reality in delisting criteria for a threatened species: The Mexican spotted owl experience

Abstract: The Mexican spotted owl (Strix occidenralis lucida) was listed as a threatened species under the Endangered Species Act (ESA) in April 1993 (USDI 1993). Concomitant with the listing of the owl, a recovery team was appointed to develop a plan to recover the owl, allowing for its removal from the list of threatened and endangered species. The recovery plan-"the plan w-was completed and accepted by the U. In developing the plan, the recovery team assembled and reviewed all existing information on the ecology of the Mexican spotted owl, existing forest conditions and trends, and potential threats to the owl. Existing infonna-tion provided a baseline understanding of owl biology and habitat correlates, which provided a basis for the general management recommendations contained within the plan. However, little reliable data were available to assess the status and trend of the owl population or owl habitat. Consequently, considerable uncertainty existed in whether or not implementation of those recommendations would provide for adequate habitat now and into the future to support a persistent owl population. Rather than recommend cessation of all management activities that constituted possible but uncertain effects,

Ecological Responses to Habitat Edges: Mechanisms, Models, and Variability Explained

Abstract: ▪ Abstract Edge effects have been studied for decades because they are a key component to understanding how landscape structure influences habitat quality. However, making sense of the diverse patterns and extensive variability reported in the literature has been difficult because there has been no unifying conceptual framework to guide research. In this review, we identify four fundamental mechanisms that cause edge responses: ecological flows, access to spatially separated resources, resource mapping, and species interactions. We present a conceptual framework that identifies the pathways through which these four mechanisms can influence distributions, ultimately leading to new ecological communities near habitat edges. Next, we examine a predictive model of edge responses and show how it can explain much of the variation reported in the literature. Using this model, we show that, when observed, edge responses are largely predictable and consistent. When edge responses are variable for the same species ...

Climate, habitat quality, and fitness in northern spotted owl populations in northwestern california

Abstract: A controversy exists in the Pacific Northwest of the United States between logging of old-growth coniferous forests and conservation of Northern Spotted Owl (Strix occidentalis caurina) populations. This species has a strong association with old-growth forests that also have economic value as timber. Research questions relevant to conservation of this species include how temporal trends in Northern Spotted Owl populations are influenced and how spatial configuration of old-growth forests affects these populations. To address these questions, we studied a population of marked Northern Spotted Owls on 95 territories in northwestern California from 1985 through 1994. We examined the mag- nitude of temporal and spatial variation in life history traits (survival, reproductive output, and recruitment), the effects of climate and landscape characteristics on temporal and spatial variation in these traits, respectively, and how this variation affected aspects of population dynamics. We used a components-of-variation analysis to partition sampling from process variation, and a model selection approach to estimate life history traits using capture- recapture and random-effects models. Climate explained most of the temporal variation in life history traits. Annual survival varied the least over time, whereas recruitment rate varied the most, suggesting a ''bet-hedging'' life history strategy for the owl. A forecast of annual rates of population change ( l), estimated from life history traits, suggested that Northern Spotted Owl populations may change solely due to climate influences, even with unchanging habitat conditions. In terms of spatial variation, annual survival on territories was positively associated both with amounts of interior old-growth forest and with length of edge between those forests and other vegetation types. Reproductive output was nega- tively associated with interior forest, but positively associated with edge between mature and old-growth conifer forest and other vegetation types. A gradient existed in territory- specific estimates of fitness derived from these life history estimates. This gradient suggested that a mosaic of older forest interspersed with other vegetation types promoted high fitness in Northern Spotted Owls. Habitat quality, as defined by fitness, appeared to buffer variation in annual survival but did not buffer reproductive output. We postulated that the magnitude of l was determined by habitat quality, whereas variation of l was influenced by recruitment and reproductive output. As habitat quality declines, variation in l should become more pronounced.

The Uses of Statistical Power in Conservation Biology: The Vaquita and Northern Spotted Owl

Abstract: The consequences of accepting a false null hypothesis can be acute in conservation biology because endangered populations leave little margin for recovery from incorrect management decisions. The concept of statistical power provides a method of estimating the probability of accepting a false null hypothesis. We illustrate how to calculate and interpret statistical power in a conservation context with two examples based on the vaquita (Phocoena sinus), an endangered porpoise, and the Northern Spotted Owl (Strix occidentalis caurina). The vaquita example shows how to estimate power to detect negative trends in abundance. Power to detect a decline in abundance decreases as populations become smaller, and, for the vaquita, is unacceptably low witin the range of estimated population sizes. Consequently, detection of a decline should not be a necessary criterion for enacting conservation measures for rare species. For the Northern Spotted Owl, estimates of power allow a reinterpretation of results of a previous demographic analysis that concluded the population was stable. We find that even if the owl population had been declining at 4% per year, the probability of detecting the decline was at most 0.64, and probably closer to 0.13; hence, concluding that the population was stable was not justified. Finally, we show how calculations of power can be used to compare different methods of monitoring changes in the size of small populations. The optimal method of monitoring Northern Spotted Owl populations may depend both on the size of the study area in relation to the effort expended and on the density of animals. At low densities, a demographic approach can be more powerful than direct estimation of population size through surveys. At higher densities the demographic approach may be more powerful for small populations, but surveys are more powerful for populations larger than about 100 owls. The tradeoff point depends on density but apparently not on rate of decline. Power decreases at low population sizes for both methods because of demographic stochasticity. En conservacion biologica, las consecuencias de aceptar hipotesis nulas falsas pueden ser muy severas puesto que las poblaciones en peligro de extincion dejan poco margen para revertir el efecto de decisiones incorrectas de manejo. El concepto de poder estadistico provee un metodo para estimar la probabilidad de aceptar hipotesis nulas falsas. Nosotros ilustramos como calcular e interpretar el poder estadistico en un contexto de conservacion con dos ejemplos basados en la vaquita (Phocoena sinus), una marsopa en peligro de extincion, y el buho moteado del Norte (Strix occidentalis caurina). El ejemplo de la vaquita muestra como estimar el poder para detectar tendencias negativas en abundancia. El poder para detectar una disminucion en la abundancia decrece a medida que las poblaciones se hacen mas pequenas, y en el caso de la vaquita, es inaceptablemente bajo para el rango de tamanos poblacionales estimados. Por consiguiente, la deteccion de una declinacion en el tamano poblacional no debe ser un criterio necesario para decretar medidas de conservacion en especies raras. En el caso del buho moteado del Norte, la estimacion del poder permite la reinterpretacion de resultados de analisis demograficos previos que concluyeron que la poblacion era estable. Nosotros encontramos que aun si la poblacion del buho moteado a estado declinando un 4% por ano, la probabilidad de detectar esta declinacion fue de a lo sumo 0.64%, y probablemente mas cercana al 0.13%. Por consiguiente, no se justificaba concluir que la poblacion era estable. Finalmente, demostramos como los calculos de poder pueden ser usados para comparar distintos metodos de monitoreo de cambios en el tamano de poblaciones pequenas. El metodo optimo de monitoreo de las poblaciones del buho moteado del Norte depende quizas tanto del tamano del area de estudio en relacion con el esfuerzo realizado como de la densidad de los aminales. A bajas densidades, la aproximacion demografica puede ser mas poderosa que la estimacion directa del tamano poblacional a partir de evaluaciones. A mayores densidades la aproximacion demografica puede ser mas poderosa para poblaciones pequenas, pero las evaluaciones son mas poderosas para poblaciones de mas de 100 buhos. El punto de relacion (tradeoff) depende de la densidad pero aparantemente no depende de la tasa de declinacion. Para tamanos poblacionales bajos, el poder decrece para ambos metodos debido a la estocasticidad demografica.

Northern spotted owls : Influence of prey base and landscape character

Abstract: We studied prey populations and the use and composition of home ranges of 47 Northern Spotted Owls (Strix occidentalis caurina) over 12 mo in five landscapes in two forest types in southwestern Oregon. We measured 1-yr home ranges of 23 owl pairs, 2-yr home ranges of 13 pairs, and 3-yr home ranges of 3 pairs. The landscapes differed in the degree to which old forest had been fragmented by wildfire and logging. Prey populations were measured at 47 sites in southwestern Oregon. Further data on prey populations were gathered on 14 sites on the Olympic Peninsula in northern Washington, where owls use larger ranges than in Oregon. Owls in Washington used - 1700 ha of old forest annually and primarily one prey species; available prey biomass was 61 g/ha. Owls in Oregon Douglas-fir (Pseudotsuga menziesai) forests used 813 + 133 ha (X + SE) of old forest annually and concentrated on two prey species that had a combined biomass of 244 g/ha. Owls in Oregon mixed-conifer forest used 454 ? 84 ha of old forest annually and three primary prey whose availability averaged 338 g/ha. The amount of old forest used by owls studied for 2 yr was 40% greater in the 2nd yr than that used in the Ist yr. No increase in use of old forest was seen in the 3rd yr in Douglas-fir forest; 50% more old forest was used in 3 yr than in the 1st yr in mixed-conifer forest. The most common prey in Washington and Oregon was the northern flying squirrel (Glaucomys sabrinus). In areas where the flying squirrel was the primary prey and where predation was intense (as judged by telemetry), flying squirrel populations were depressed. The addition of medium-sized mammal species, especially woodrats (Ne- otoma spp.), to the prey base appeared to reduce markedly the amount of old forest used for foraging. Owls traversed 85% more Douglas-fir forest and 3 times more mixed-conifer forest in the heavily fragmented areas than in the lightly fragmented areas. Overlap among pairs and separation of birds within pairs in space increased with fragmentation. In the most heavily fragmented landscape, social structure appeared to be abnormal, as judged by the proportion of adult-subadult pairs, instances of adult nomadism, and overlap among the home ranges of pairs. The pattern of fragmentation affected the ability of owls to find concentrations of old forest in the landscapes. Even so, almost all the owls consistently selected old forests for foraging and roosting; only one owl selected a younger type as part of its foraging range. Selection of old forest was significant at three levels: landscape, annual home ranges of pairs, and foraging and roosting sites of individuals. The most important prey species, the northern flying squirrel, was twice as abundant in old forest as in young forest in all areas. Landscape indices (dominance, contagion, variance in density of old forest) had less predictive ability than indices based on owl home ranges because owls selected areas of concentrated old forest and because patterning was complex, reflecting four processes, each operating at a different scale: physiography, human land ownership (259-ha scale), history of catastrophic fires, and history of small-scale fires and timber harvesting.