--We describe local, regional, and annual variation in diets of northern Spotted Owls (Strix occidentalis caurina) in Oregon based on 24 497 prey collected at 1118 owl territories in 1970-2003. The sample included 91.5% mammals, 4.3% birds, 4.1% insects, and 0.1% other prey. The diet included a131 species, including 49 mammals, 41 birds, 3 reptiles, 1 frog, 1 crayfish, I scorpion, 2 snails, and 33 species of insects. On average, 91.9 + 0.3% (SE) of prey in the diet were nocturnal animals, 3.3 + 0.2% were diurnal, and 4.8 + 0.2% were active both day and night. Of the prey captured, 50.5 + 0.8% were arboreal, 18.7 _ 0.7% were scansorial, 4.8 + 0.2% were aerial, and 26.0 + 0.7% were terrestrial. Mean mass of prey was 116.6 _+ 6.5 g. Diets varied among owl territories, geographic regions, and years; but were generally dominated by four to six species of nocturnal mammals, including northern flying squirrels ( Glaucomys sabrinus), woodrats (Neotoma fuscipes and N. cinerea), red tree voles (Arborimus Iongicaudus), western red-backed voles (Clethrionomys californicus), deer mice (Peromyscus maniculatus), or gophers (Thomomys spp.). Estimates of dietary evenness were low, indicating diets dominated by a tkw species of mammals. Forest management practices that produce healthy populations of arboreal and scansorial mammals such as flying squirrels, woodrats, and red tree voles should benefit northern Spotted Owls in Oregon and Washington.

We studied the dispersal behavior of 1,475 northern spotted owls (Strix occidentalis caurina) during banding and radio-telemetry studies in Oregon and Washington in 1985-1996. The sample included 324 radio-marked juveniles and 1,151 banded individuals (711 juveniles, 440 non-juveniles) that were recaptured or resighted after dispersing from file initial banding location. Juveniles typically left the nest during the last week in May and the first two weeks in June ((x) over bar +/- SE = 8 June +/- 0,53 days, n = 320, range = 15 May-1 July). and spent an average of 103.7 days in the natal territory after leaving the nest (SE = 0.986 days, n = 137, range = 76-147 days). The estimated mean date that juveniles began to disperse was 19 September in Oregon (95% CI = 17-21 September) and 30 September in Washington (95% CI = 25 September-4 October). Mean dispersal dates did not differ between males and females or among years. Siblings dispersed independently. Dispersal was typically initiated with a series of rapid movements away from the natal site during file first few days or weeks of dispersal, Thereafter, most juveniles settled into temporary home ranges in late October or November and remained there for several months, In February-April there was a second pulse of dispersal activity, with many owls moving considerable distances before Scaling again in their second summer, Subsequent dispersal patterns were highly variable, with Some individuals settling permanently in their second summer and others occupying a series of temporary home ranges before eventually settling on territories,when they were 2-5 years old. Final dispersal distances ranged from 0.6-111.2 km for handed juveniles arid 1,8-103.5 km for radio-marked juveniles. The distribution of dispersal distances was strongly skewed towards shorter distances, with only 8.7% of individuals dispersing more than 50 km. Median natal dispersal distances were 14,6 kin for banded malus. 13.5 kill for radio-marked males, 24.5 km for banded females, and 22.9 km for radio-marked females. On average, banded males and females Settled within 4.2 and 7.0 territory widths of their natal sites, respectively. Maximum and final dispersal distances were largely independent of the number of days that juveniles were tracked, Although statistical tests of dispersal direction based on all owls indicated that direction of natal dispersal was non-random, the mean angular deviations and 95% CI's associated with the samples were large, and r-values (vector length) were small. This lead us to conclude that significant test results were the result of large sample size and were not biologically meaningful. Our samples were not large enough to test whether dispersal direction from individual territories was random.In the sample of radio-marked owls, 22% of males and 44% of females were paired at I year of age, but only 1.5% of males arid 1.6% of females were actually breeding at I year of age. At 2 years of age, 68% of males and 77% of females were paired. but only 5.4% of males and 2.6% of females were breeding. In contrast to the radio-marked owls, most juveniles that were banded and relocated at I or 2 scars of age were paired, although few were breeding. Although recruitment into the territorial population typically occurred when owls were 1-5 years old, 9% of handed juveniles were not recaptured until they were >5 years old. We suspect that our estimates of age at recruitment of banded owls are biased high because of the likelihood that some individuals were not recaptured in the first year that they entered the territorial population.A minimum of 6% of the banded, non-juvenile owls on our demographic study areas changed territories each year (breeding dispersal), The likelihood of breeding dispersal was higher for females, young owls, owls that did not have a mate in the previous year, and owls that lost their Mate from the previous year through death or divorce. Mean and median distances dispersed by adults were shorter than for juveniles and did not differ between the sexes or study areas ((x) over bar = 6.1 km median = 15 km). Owls that were 1-2 years old tended to disperse father than owls that were >2 years old, The direction of post-natal dispersal did not differ from random.The large nonforested valleys of western Oregon (Willamette, Umpqua, Rogue Valleys) acted as barriers to dispersal between the Coast Ranges and the Cascade Mountains. However, dispersal did occur between the Coast Ranges and Cascade Mountains in the forested foothills be between the non-forested valleys. Forest landscapes traversed by dispersing owls typically included a fragmented mosaic of roads, clear-cuts, non-forest areas, and a variety of forest age classes ranging from young forests on cutower areas, to old-growth forests greater than or equal to250 years old.Our data fit the general pattern observed in birds in that females dispersed farther than males and dispersal distances were negatively skewed towards short distance dispersers. Comparison of data from radio-marked arid banded owls demonstrated that the negatively skewed distribution of dispersal distances represented the actual distribution of dispersal distances, arid was not the result of small study area bias on recaptures. We found no correlation between dispersal distance and age at first breeding, which suggests that reproductive fitness is not affected by dispersal distance. We observed only 3 cases of close inbreeding (parent-offspring or sibling pairs) in thousands of pairs of spotted owls, suggesting that dispersal results in a very low incidence of close inbreeding in the spotted owl. However, Inbreeding with more distant relatives was common.

Conflicts between the needs of the Northern Spotted Owl (Strix occidentalis caurina) and the maintenance of a timber -based economy in the Pacific Northwest have motivated research on the habitat and area requirements of the owl. The Northern Spotted Owl has been studied extensively throughout its range and consistently has been found to select older forest stands for foraging, roosting, and nesting (reviewed in Thomas et al. [1990]). At least six hypotheses have been proposed to account for selection of older forests by Spotted Owls (Forsman et al. 1977, 1982, 1984, Carey et al. 1990, 1992, Rosenberg and Anthony 1992). Two of these relate to their prey. The prey hypotheses suggest that prey are more available to Spotted Owls by either or both of two mechanisms: (1) prey are simply more abundant in older forests (prey abundance hypothesis), and (2) prey are more efficiently hunted in older forests because of an increase in the ability of owls to forage through more open understory structure (prey availability hypothesis). Carey et al. (1992) recently reported on associations between Spotted Owls and their prey in Oregon and Washington. They concluded that the abundance of prey across a landscape determined the carrying capacity for Spotted Owls and that within-landscape features such as stand age and forest fragmentation affected the abundance and demographic characteristics of prey. Northern flying squirrels (Glaucomys sabrinus) and dusky-footed and bushy-tailed woodrats (Neotoma fuscipes and N. cinerea, respectively) are the most common prey of the Northern Spotted Owl throughout its range, constituting the majority of the biomass consumed by owls (Forsman et al. 1984). Carey et al. (1992) concluded that northern flying squirrels were more abundant in older forests, populations were more

Unlike previous spotted owl (Strix occidentalis) habitat association studies. we restricted our inquiry to the old-forest type and thus explored the association of spotted owls with habitat distribution as opposed to habitat type. We compared old-forest distribution around 126 northern spotted owl (S. o. caurina) nests in 70 pair territories, 14 nonreproductive spotted owl activity centers and 104 points drawn randomly from old forest (closed canopy, >80 yr) in the central Cascade Mountains of Oregon. We quantified the percentage of old forest within 50 concentric circular plots (0.1-5.0-km radii) centered on each analyzed point, and we used logistic regression to make spatially explicit inferences. Owl nests were surrounded by more old forest in plots with 0.2-0.8-km radii (P < 0.05). Results suggested the landscape scales most pertinent to northern spotted owl nest-site positioning in this study were (in descending order) (1) the surrounding 15 ha (approx 200-m radius), (2) the surrounding 30-115 ha (approx 300-600-m radius), (3) the surrounding 200 ha (800-m radius), and (4) possibly the surrounding 700 ha (1,500-m radius). Nests were associated with higher proportions of old forest near the nest, implying that the arrangement of habitat was important for nest-site selection, positioning, or both. The 70 territories of nesting owls had more old forest on average than did the 14 nonreproductive owl sites, and the probability that 3 pair nested at least once during thf study was positively associated with area of old-forest habitat in all radii studied. Because spotted owls in the central Cascade Mountains of Oregon are known to have home ranges that average 1,700 ha, our results apply to nest-site location on the landscape and not to the amount of habitat necessary for pair persistence or successful reproduction.

Damage to trees by black bears (Ursus americanus) is an ongoing problem in west-coastal Noah America. We studied damage to Douglas-fir (Pseudotsuga menziesii) during spring by comparing food habits of bears between an area with high damage (north, (x) over bar(N) = 29.4 trees damaged/ha, SE = 6.9) and an area with low damage (south, (x) over bar(S) = 2.7 trees damaged/ha, SE = 1.6). We surveyed 40 forested stands in each area to measure and describe bear damage and to determine if site factors were related to damage levels. Analysis of seats revealed differences in spring diets that included a higher frequency of berry-producing shrubs seats from the south area (P < 0.01) and a higher frequency of forbs (P < 0.01) in the north area. Site characteristics differed between stands with and without bear damage (P < 0.01). Forest stands with bear damage (n = 33) had a lower density of trees > 40 cm dbh (P < 0.01), lower total basal area (P < 0.01), occurred on less steep slopes (P < 0.01), and differed by aspect (cosine[aspect]: P < 0.01) compared to forest stands without bear damage (n = 47). Most damage occurs during spring, a season frequently associated with nutritionally poor foods for bears. This is also when carbohydrate production peaks in conifers and cambial zones have the most mass. Stands with prominent damage resemble continuous patchy habitats. Clustered food items appear to be efficiently located and exploited in continuous patchy habitats, even if foragers can only poorly estimate resource distribution. Cambium-feeding may be an energetically viable option for some bears. We recommend altering forest structure in stands vulnerable to bear damage and providing patches of nutritious bear foods as a test to decrease bear damage by reducing the foraging efficiency of bears feeding on cambium.

We describe the structure of forests at 105 nest sites of northern spotted owls (Strix occidentalis caurina) in the Klamath, Coast, and Cascade provinces of western Oregon and the Olympic province of Washington. This information is critical for management and recovery of this threatened species. We compared forest stand data at nest sites with data from 105 random sites, using logistic regression for 1:1 matched pairs. All random sites were located in older forests (overstory trees >50 cm diameter at breast height [dbh]) within owl home ranges. Most nests in Oregon were in Douglas-fir (Pseudotsuga menziesii) trees (88%), whereas nests in the Olympic province were equally divided among Douglas-fir, western hemlock (Tsuga heterophylla), and western redcedar (Thuja plicata). In all 4 provinces, nests were most often located in live trees (73-97%) with broken tops (60-93%), most of which were fire scarred (77-83%). Mean diameter of all nest trees (n = 105) was 139.4 +/- 5.2 cm ((x) over bar +/- SE). Most nests (83%) were in cavities; of the 17% nests that were in platforms, most (67%) were in the Klamath province. The majority of nest sites (95%) were found from the middle to the bottom of slopes. Mean aspects at nest sites were southerly in Oregon and northwesterly in the Olympics. Elevations at nest sites were lower than at their paired random sites, and evidence of fire was present at 86% of nest sites. Univariate analyses indicted nest sites were associated with structurally diverse older forests exhibiting characteristics typical of old-growth forests in the Pacific Northwest, Mean diameter of large trees (>100 cm dbh) was greater at nest than random sites (130.6 +/- 1.8 cm vs. 123.1 +/- 1.3 cm; P < 0.001), which suggested trees may be older at nest sites or nest sites may have greater potential for tree growth. In comparison to random sites, nest sites had a greater basal area and density of trees, especially trees <53 cm dbh and <38 m in height. The greater horizontal and vertical density of trees at nest sites provided a denser cover in the multiple layers of canopy than at random sites. Basal area and density of broken-top trees (>53.3 cm dbh with 1 or more secondary crowns) were also greater at nest sites than at random sites in all physiographic provinces (P < 0.001), as was the volume of logs in Decay Classes 4 and 5 (P < 0.029). The best multivariate model based on the lowest Akaike's Information Criterion (AIC) value indicated the combination of greater basal area of broken-top trees, greater basal area of small trees in Class 1, larger volumes of logs in Decay Class 5, and lower elevations best distinguished nest sites from random sites. If silvicultural prescriptions are designed in an attempt to produce the stand structure of nesting habitat, they must consider the roles fire and other disturbances have played in creating the diverse stand structure found at nest sites.

Despite the general lack of theoretical or empirical support, biological corridors are assumed to mitigate the detrimental effects of habitat fragmentation by increasing landscape connectivity. To test the hypothesis that mechanisms which affect immigration rates from a source to a target patch are affected by the presence of a corridor in an otherwise unsuitable matrix, we created two strongly contrasting pathways in replicated field experiments. One pathway type included only bare mineral soil, the other included a potential corridor. We conducted these experiments with Ensatina eschscholtzii, a salamander in the family Plethodontidae. Pathways with surface organic material removed provided a harsh environment for E. eschscholtzii, which was reflected by lower selection, shorter residency time, and higher movement rates than on pathways that contained vegetation (corridor pathways). However, the numbers of E. eschscholtzii reaching target patches connected by corridor pathways were greater than those reaching target patches connected by bare pathways only in plots in which the matrix environment seemed most severe. Our results suggest that identifying candidate corridor areas on conservation maps might be difficult because animals may show compensatory behavioral responses to different types of habitat separating source and target patches. We argue that knowledge of a species' habitat-specific dispersal behaviors is critical to reliably designating corridors as functional components of reserve design.

The probability of successful natal dispersal may influence the viability of northern spotted owl (Strix occidentalis caurina) populations within fragmented forests. We tested 6 null hypotheses examining the relations between habitat selection, forest fragmentation, and the probability of mortality for juvenile northern spotted owls during natal dispersal in western Oregon, 1882-85. Older forest (old-growth and mature stands) was the vegetation type used most frequently during transience (35.3%) and colonization (61.2%), and spotted owls selected closed-canopy forests over open-canopy forests during both phases of dispersal (P < 0.05). The hypotheses that spotted owl habitat selection was independent of forest fragmentation were not rejected for either transient (P = 0.51) or colonization (P = 0.13) dispersal. Likewise, net dispersal distance was independent of forest fragmentation (P = 0.92). Use of open sapling stands during transient dispersal decreased the probability of mortality (Wald test = 2.21, P = 0.03), whereas use of clearcuts during colonization dispersal increased the probability of mortality (Wald test = 1.95, P = 0.03). Net dispersal distance did not affect the probability of mortality (P = 0.67), yet a negative relation existed between dispersal distance and the amount of clearcut used during transient dispersal (P < 0.005). These results provide additional evidence of the selection of older forests by spotted owls and how their natal dispersal may be affected by harvesting such forests; particularly, that use of clearcuts may decrease the probability of successful natal dispersal.

H abitat loss and fragmentation are among the most pervasive threats to the conservation of biological diversity (Wilcove et al. 1986, Wilcox and Murphy 1985). Habitat fragmentation often leads to the isolation of small populations, which have higher extinctionrates (e.g., Pimm et al. 1988). Ultimately, the processes of isolation and population extinction lead to a reduction in biological diversity. Concern for this loss has motivated conservation biologists to discuss the actions that are needed to increase the effective size of local populations. Predominant among these possible str,ltegies has been the recommendation that corridors be induded in conservation plans (Figure 1) to increase the connectivity of otherwise isolated patches (Meffe and Carroll1994). The indusion of corridors in reserve designs has become an importa nt conservation tactic for protecting biological diversity. This strategy was motivated by theoretical and empirical observations demonstrating that increased interchange of in-

Landscape characteristics near 20 northern spotted owl (Strix occidentalis caurina) nests were compared with 20 paired random sites for 4 concentric circular plot sizes in southwestern Oregon. Nest sites contained significantly more old-conifer forest than random sites at all 4 plot sizes of 118, 471, 1,057, and 1,826 ha. With the exception of open canopy old-conifer at the 1,826-ha plot size, we found no significant differences between nest and random sites in the proportion of open sapling, hardwood mix, pole/young, and open canopy old-conifer forest for all plot sizes, but the tests have a low power due to the small sample sizes. Nest patches were larger than the largest old conifer patches found in each random plot. Conclusions regarding most landscape pattern variables and owl nest site selection were not possible because landscape pattern variables were highly correlated with the amount of old-conifer forest. We developed a reproductive index (RI) that should be useful for comparing reproductive rates among nests where the reproductive outcomes for individual nests are not available for the exact same years. Our preliminary results suggest that spotted owl reproductive rates may be directly related to the proportion of old-conifer forest in the landscape.

Demographic characteristics of the Northern Spotted Owl (Strix occidentalis caurina) were studied on the Eugene District Bureau of Land Management, central Oregon Coast Ranges from 1989-1995. Survival rates were estimated from capture histories of banded owls using Cormack-Jolly-Seber open population models. We banded 233 owls, including 119 that were greater than or equal to 3 years old, 15 that were 1 or 2 years old, and 99 juveniles. Among year variation in the proportion of pairs nesting and fecundity of females was significant (P < 0.001). Estimates of apparent annual survival from the selected capture-recapture models were 0.306 (SE = 0.064) for juveniles and 0.875 (SE = 0.018) for subadult and adult owls combined. The estimated annual rate of population change (0.939, SE = 0.045) was < 1.00 (P 0.005) over the 6 years of study, suggesting an average population decline of 6. 1 percent per year. Counts of territorial owls decreased by 37 percent from 1990-1995 on the Wolf Creek density study area, a smaller area within the larger surrounding study area. We suggest the owl population decline was due to the reduction of spotted owl habitat.

Journal Article Assessment of Terrestrial Species and Ecosystems Get access E. Charles Meslow, E. Charles Meslow 1Economist, USDA Forest Service, New Orleans, LA Search for other works by this author on: Oxford Academic Google Scholar Richard S. Holthausen, Richard S. Holthausen 2Economist, USDA Forest Service, New Orleans, LA Search for other works by this author on: Oxford Academic Google Scholar David A. Cleaves David A. Cleaves 3Economist, USDA Forest Service, New Orleans, LA Search for other works by this author on: Oxford Academic Google Scholar Journal of Forestry, Volume 92, Issue 4, April 1994, Pages 24–27, https://doi.org/10.1093/jof/92.4.24 Published: 01 April 1994

EcologyVolume 75, Issue 5 p. 1512-1515 Article Northern Spotted Owls: Influence of Prey Base--A Comment Daniel K. Rosenberg, Daniel K. RosenbergSearch for more papers by this authorCynthia J. Zabel, Cynthia J. ZabelSearch for more papers by this authorBarry R. Noon, Barry R. NoonSearch for more papers by this authorE. Charles Meslow, E. Charles MeslowSearch for more papers by this author Daniel K. Rosenberg, Daniel K. RosenbergSearch for more papers by this authorCynthia J. Zabel, Cynthia J. ZabelSearch for more papers by this authorBarry R. Noon, Barry R. NoonSearch for more papers by this authorE. Charles Meslow, E. Charles MeslowSearch for more papers by this author First published: 01 July 1994 https://doi.org/10.2307/1937475Citations: 6AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Citing Literature Volume75, Issue5July 1994Pages 1512-1515 RelatedInformation

Current allocations of habitat for pileated woodpeckers (Dryocopus pileatus) on National Forests in the western United States may be inadequate because of previous methods used to calculate this species' home range. Hence, we used radio telemetry to determine home ranges (n = 11) and habitat use (n = 14) of pileated woodpeckers in the Coast Ranges of western Oregon during the summers of 1982-85. Home ranges for individual adult birds, after young had fledged, averaged 478 ha. Home ranges for pairs were larger. Home ranges were larger than those reported in other studies. Pileated woodpeckers preferred (P < 0.05) forest vegetation classes that were older than 40 years and deciduous riparian habitats for foraging and other diurnal activities more than classes that were younger than 40 years. Nesting and roosting occurred only in forest stands older than 70 years. The amount of foraging habitat within the home ranges averaged 310 ha; whereas the amount of nesting and roosting habitat averaged 225 ha. Because pileated woodpeckers forage in immature forests, they may not be good management indicator species for mature and old-growth forest habitats.

We compared survival, reproduction, and body mass of radio-marked and non-radio-marked spotted owls (Strix occidentalis) to determine if backpack radios influenced reproduction or survival. In most study areas and years, there were no differences (P>0.05) in survival of males and females or in survival of radio-marked versus banded owls. There was no difference (P=0.31) in mean mass of owls before and after they had worn radio transmitters. Radio-marked owls produced fewer (P<0.01) young than did owls that were not radio-marked

We investigated how the amount of old-growth and mature forest influences the selection of nest sites by northern spotted owls (Strix occidentalis caurina) in the Central Cascade Mountains of Oregon. We used 7 different plot sizes to compare the proportion of mature and old-growth forest between 30 nest sites and 30 random sites. The proportion of old-growth and mature forest was significantly greater at nest sites than at random sites for all plot sizes (P less-than-or-equal-to 0.01). Thus, management of the spotted owl might require setting the percentage of old-growth and mature forest retained from harvesting at least 1 standard deviation above the mean for the 30 nest sites we examined.

Crustose coralline algae were the prevalent cover among sessile organisms that paved or grew near the substratum, and also the most commonly overgrown species in a giant kelp Macrocystis pyrifera (L.) C.A. Agardh forest located off San Nicolas Island, California. Giant kelp was the largest and most conspicuous species that overgrew large patches of the substrata; overgrowth among turf organisms also appeared common. To determine the effects of giant kelp holdfasts on crustose coralline algae and other turf organisms,“artificial holdfasts” were placed on 0.125-m2 plots for 5, 8 and 12 months. In these treatments, 50–57% of the crustose coralline algae survived. Because these algae also recruited while covered, the total cover (survivorship plus recruitment) differed by only 7–26% from that sampled at the start of the study. The decline of these algae in control plots was similar to that in the treatment plots mostly because of overgrowth by sessile invertebrates. Bryozoans increased markedly on the control plots, whereas 0–12% survived in the treatment plots. Bryozoans and sponges also recruited under the artificial holdfasts. Some arborescent turf algae survived in the 5- and 8-month treatments; articulated coralline algae survived better than did foliose algae. High survival recruitment of crustose coralline algae while overgrown contributed to their prevalence in benthic communities.