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Cynthia J. Zabel

Bio: Cynthia J. Zabel is an academic researcher from United States Forest Service. The author has contributed to research in topics: Northern spotted owl & Northern flying squirrel. The author has an hindex of 13, co-authored 20 publications receiving 774 citations.

Papers
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Journal ArticleDOI
TL;DR: Data indicate that prey species are a better predictor of home-range size than the proportion of older forest within spotted owl home ranges in the Klamath Province of northwestern California and southwestern Oregon, an area that is predominantly late-successional forest.
Abstract: Correlations between the home-range size of northern spotted owls (Strix occidentalis caurina) and proportion of their range in old-growth forest have been reported, but there are few data on the r...

132 citations

Journal ArticleDOI
TL;DR: Flying squirrels were not old-growth specialists; however, low densities in shelterwood stands suggest that heavy logging and intensive site preparation negatively affected flying squirrel populations.
Abstract: The northern flying squirrel (Glaucomys sabrinus) is the primary prey of northern spotted owls (Strix occidentalis caurina) and California spotted owls (S. o. occidentalis) throughout much of the owls' ranges. Flying squirrel abundance patterns, however, are poorly documented. Using capture-recapture techniques to estimate density, we compared flying squirrel densities among 3 types of fir (Abies spp.) forests in Lassen National Forest, northeastern California. We compared densities between 3 each of old and shelterwood-logged fir stands in 1990 and among 4 each of old, shelterwood, and young fir stands in 1991-92. Shelterwood stands had been logged and had undergone site preparation 5 years prior to our study. In 1990 flying squirrel density was greater in old (? = 2.76 squirrels/ha, SE = 0.55) than in shelterwood (? = 0.31 squirrels/ha, SE = 0.11) stands (P = 0.005). In 1991-92 density varied (P = 0.001) among the 3 stand types, averaging 3.29 squirrels/ha (SE = 0.63) in old, 2.28 squirrels/ha (SE = 0.18) in young, and 0.37 squirrels/ ha (SE = 0.17) in shelterwood stands. Body mass of adult males and females and recapture rate did not differ (M, P = 0.438; F, P = 0.983; P = 0.218, respectively) between old and young stands, and percent juveniles captured was greater (P = 0.052) in old than in young stands. Diet analyses were consistent with other studies and indicated that sporocarps of hypogeous fungi were a common food source. Frequency of hypogeous sporocarps was correlated (r s = 0.860, P < 0.001) with flying squirrel density, but cavity density and understory cover were not (P = 0.344 and 0.217, respectively). Flying squirrels were not old-growth specialists; however, low densities in shelterwood stands suggest that heavy logging and intensive site preparation negatively affected flying squirrel populations.

113 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compared bat activity among three size classes of streams and upland sites in a northwestern California watershed during summers 1996 and 1997 and found that bat activity was greatest along medium and large intermittent streams, was intermediate at small intermittent streams and was least at upland site.
Abstract: Bats are known to use areas above perennial streams and rivers for foraging and traveling; however, little is known about bat use of smaller streams that flow intermittently. We compared bat activity among 3 size classes of streams and upland sites in a northwestern California watershed during summers 1996 and 1997. Stream size was classified based on channel width. Ultrasonic Anabat II® bat detectors were placed in stream channels and at upland sites, and bat activity was recorded remotely at night. Analysis of bat detector data revealed a significant difference in activity among the 4 habitat types in both years. In 1996, bat activity was greatest along medium and large intermittent streams, was intermediate at small intermittent streams, and was least at upland sites. In 1997, a similar pattern was found, but no significant difference was found in bat activity between small stream and upland sites. To determine species presence, bats were captured in mist nets at stream sites with the highest bat activity. Results are presented indicating differences in number of captures by species between medium and large streams.

83 citations

Journal ArticleDOI
TL;DR: Results are comparable to findings for other forest-dwelling bat species which conclude that management of day roost habitat requires large numbers of tall snags in early to medium stages of decay.
Abstract: Understanding habitat relationships of forest-dwelling bats has become a wildlife management priority during the past decade. We used radiotelemetry to examine the use of day roosts by fringed myotis (Myotis thysanodes) in a Douglas-fir (Pseudotsuga menziesii) forest in northern California, We located 52 roosts in 23 trees and compared the characteristics of roost sites and structures to random sites and structures. All roost trees were snags in early to medium stages of decay. Bats switched roosts often, and the number of bats exiting roosts varied from 1-88. The most important factor that discriminated roost sites from random sites was 5.4 more snags ≥30 cm dbh at roost sites. Roost sites also had 11% less canopy cover and were 41 m closer to stream channels than random sites. Roost snags were 27 m taller and had diameters 42 cm larger than random snags in the watershed and were 21 m taller and had diameters 30 cm larger than snags nearby the roost. Our results are comparable to findings for other forest-dwelling bat species which conclude that management of day roost habitat requires large numbers of tall snags in early to medium stages of decay.

60 citations

Journal ArticleDOI
TL;DR: Monitoring reproductive success of northern spotted owls on Simpson Timber Company's managed, young-growth forests in northwestern California found Spotted owls that chose younger stands with smaller trees mav have benefited from higher woodrat availability in young stands.
Abstract: We monitored reproductive success of northern spotted owls (Strix identalis caurina) at 51 sites on Simpson Timber Company's (STC) managed, young-growth forests in northwestern California from 1991 to 1995. We compared habitat characteristics between sites with high and low fecundity at 5 spatial scales (concentric circles of 7. 50, 114, 203, and 398 ha), using 2 stratifications of annual reproductive success (upper 50% vs. lower 50% and upper 25% vs. lower 75% of the proportion of years when ≥1 owlet fledged). Habitat features included number of residual trees per hectare and mean proportion of 6 categories of stand age and 4 categories of basal area. Using the 50th percentile categories, we found there were higher proportions of age class 21-40 years and basal area classes 23-45 and 46-69 m 2 /ha (P ≤ 0.05), but lower proportions of recent clearcuts (0-5 yr) and basal area >69 m 2 /ha (P ≤ 0.05) at sites with high reproductive success. Using the upper 25% and lower 75% categories, we found there were higher proportions of basal area class 23-45 m 2 /ha, lower proportions of 61-80-year-old stands and more residua trees per hectare at sites with high reproductive success (P ≤ 0.05). We also compared random sites to occupied sites via the above parameters, Spotted owl sites contained lower proportions of basal area class 69 m 2 /ha than did random sites (P < 0.05). There was less young forest (6-40 vr) and more forest of age class 41-60 vears at spotted owl than at random sites (P < 0.05). Low prey abundance around spotted owl nest sites, roost sites, or both mav explain why older stands with more basal area were found in higher proportions at sites with lower fecundity. Spotted owls that chose younger stands with smaller trees mav have benefited from higher woodrat (Neotoma fuscipes) availability in young stands. Managing habitat by retaining residual trees and limiting clearcutting to at least 1.1 km bevond lest sites may prove useful in increasing reproductive success of northern spotted owls.

53 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors identify four fundamental mechanisms that cause edge responses: ecological flows, access to spatially separated resources, resource mapping, and species interactions, and 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.
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 ...

1,244 citations

Journal ArticleDOI
Caroline M. Pond1
TL;DR: This book is based on a symposium organized by the Entomological Society of America in 1980 and will prove to be an important book in bringing together recent research on the mating systems of orthopterans, and discussing their behaviour in the light of current theory in behavioura].

911 citations

Journal ArticleDOI
TL;DR: The diversity of life in headwater streams (intermittent, first and second order) contributes to the biodiversity of a river system and its riparian network, thus providing habitats for a range of unique species as mentioned in this paper.
Abstract: The diversity of life in headwater streams (intermittent, first and second order) contributes to the biodiversity of a river system and its riparian network. Small streams differ widely in physical, chemical, and biotic attributes, thus providing habitats for a range of unique species. Headwater species include permanent residents as well as migrants that travel to headwaters at particular seasons or life stages. Movement by migrants links headwaters with downstream and terrestrial ecosystems, as do exports such as emerging and drifting insects.

677 citations

Journal ArticleDOI
TL;DR: It is illustrated that resource selection models are part of a broader collection of statistical models called weighted distributions and recommend some promising areas for future development.
Abstract: We review 87 articles published in the Journal of Wildlife Management from 2000 to 2004 to assess the current state of practice in the design and analysis of resource selection studies. Articles were classified into 4 study designs. In design 1, data are collected at the population level because individual animals are not identified. Individual animal selection may be assessed in designs 2 and 3. In design 2, use by each animal is recorded, but availability (or nonuse) is measured only at the population level. Use and availability (or unused) are measured for each animal in design 3. In design 4, resource use is measured multiple times for each animal, and availability (or nonuse) is measured for each use location. Thus, use and availability measures are paired for each use in design 4. The 4 study designs were used about equally in the articles reviewed. The most commonly used statistical analyses were logistic regression (40%) and compositional analysis (25%). We illustrate 4 problem areas in resource selection analyses: pooling of relocation data across animals with differing numbers of relocations, analyzing paired data as though they were independent, tests that do not control experiment wise error rates, and modeling observations as if they were independent when temporal or spatial correlations occurs in the data. Statistical models that allow for variation in individual animal selection rather than pooling are recommended to improve error estimation in population-level selection. Some researchers did not select appropriate statistical analyses for paired data, or their analyses were not well described. Researchers using one-resource-at-a-time procedures often did not control the experiment wise error rate, so simultaneous inference procedures and multivariate assessments of selection are suggested. The time interval between animal relocations was often relatively short, but existing analyses for temporally or spatially correlated data were not used. For studies that used logistic regression, we identified the data type employed: single sample, case control (used-unused), use-availability, or paired use-availability. It was not always clear whether studies intended to compare use to nonuse or use to availability. Despite the popularity of compositional analysis, we do not recommend it for multiple relocation data when use of one or more resources is low. We illustrate that resource selection models are part of a broader collection of statistical models called weighted distributions and recommend some promising areas for future development.

649 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied a population of marked Northern Spotted Owl (Strix occidentalis caurina) on 95 territories in northwestern California from 1985 through 1994 and found that annual survival varied the least over time, whereas recruitment rate varied the most, suggesting a "bet-hedging" life history strategy for the owl.
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.

550 citations