Chris C. Maguire

SNAGS, CAVITY-NESTING BIRDS, AND SILVICULTURAL TREATMENTS IN WESTERN OREGON

Abstract We examined cavity-nesting bird use of natural snags (n = 221) and 10- to 12-year-old snags (n = 836) created by topping mature conifers in 3 silvicultural treatments (group-selection cuts, 2-story regeneration harvests, clearcuts with retained trees) and 2 snag arrangements (clustered, scattered) in 30 Douglas-fir (Pseudotsuga menziesii) stands in the Oregon Coast Range. Eight bird species nested in created snags. Open-canopy stands (2-story and clearcut treatments) had higher levels of avian nesting, species richness, and species diversity compared to closed-canopy, group-selection stands. We did not find a difference in nesting levels between clustered and scattered snags. In created snags, most active nests were in the top 25% of the bole, cavity entrances typically faced northeast, and the presence of dead branches did not alter use of snags for nesting. Topped conifers that remained alive (n = 102) were rarely used for nesting or foraging. Since the last survey 6 years prior to our survey, the number of cavities per created snag per silvicultural treatment increased 3.3- to 6-fold, and we observed 4 additional avian species nesting; 3 were secondary cavity nesters. Total cavities per snag averaged 5.1, 4.3, and 2.5 for created snags, natural snags >12 years old, and natural snags <12 years old, respectively. Only 1 created snag fell in the decade since topping. Natural new snag recruitment resulting from residual green tree mortality was highest in 2-story stands (0.76 snag/ha) and lowest in clearcuts (0.20 snag/ha). Snags created by topping large conifers provided nesting and foraging structures for cavity-nesting birds under a range of silvicultural conditions, and use was influenced more by residual green tree density than snag arrangement. In addition, created snags increased in value for birds through their first decade (88% had cavities). Because snags created by topping last long and are readily used by birds, they should be considered a management option to improve avian habitat in managed forests.

Comparative Effectiveness of Three Techniques for Salamander and Gastropod Land Surveys

Abstract We compared the effectiveness and efficiency of three terrestrial salamander and gastropod trapping techniques: pitfall traps, ground searches and cover boards. The study was conducted on 18 stands with three management histories in the Umpqua National Forest, southern Oregon Cascades. A total of 648 pitfall traps were open for 28 consecutive days in fall 1999. Two hundred twelve amphibians (eight species) and 202 gastropods (six species) were captured. Also in fall 1999, 36 h of ground searches covering 3600 m2 resulted in the detection of 19 amphibians (two species) and 130 gastropods (six species). Four cover boards (100 × 100 cm) in stacks of two were placed in each stand and checked four times in fall 1999 and once in spring 2000 after snow melt. Cover boards concealed no amphibians and only two gastropods (one species). Pitfall traps were more efficient at capturing amphibians than ground searches (0.41 vs. 0.25 captures per hour of effort), but less efficient at capturing gastropods than ground searches (0.39 vs. 1.73 captures per hour of effort). Cover boards as used were ineffective at capturing either amphibians or gastropods. Climatic conditions of the southern Oregon Cascades likely influenced the results.

A New Elevation Record for the Red Tree Vole in Oregon: Implications for National Forest Management

Abstract We document the capture of a red tree vole (Arborimus longicaudus) at a new location and higher elevation than previously recorded for the species. This finding shows that the red tree vole occurs outside the current survey and management areas designated for its protection in Oregon federal forests.

Incidental captures of birds in small-mammal traps: a cautionary note for interdisciplinary studies

Abstract Although benefits of interdisciplinary studies are numerous, potential exists for data acquisition for some aspects of such studies to impact data acquisition for other aspects. This may be particularly true in studies involving both trapping of small mammals and assessment of bird populations. We summarize the incidence of birds captured during 8 research projects in Massachusetts, Oregon, and Washington that used 5 types of small-mammal traps, and discuss possible impacts of small-mammal trapping on bird surveys and possible mitigation measures. In these studies, 867 birds representing 17 species were captured in 703,138 total trap-nights (TN). The song sparrow (Melospiza melodia), spotted towhee (Pipilo maculatus), Steller’s jay (Cyanocitta stelleri), and gray jay (Perisoreus canadensis) accounted for 86% of all bird captures; ground-foraging species accounted for 54% of all bird captures. Relatively high capture rates were observed in Sherman (H. B. Sherman Traps, Inc., Tallahassee, Flor.) and Tomahawk traps (Tomahawk Live Trap Co., Tomahawk, Wisc.) (4.1 and 9.8 birds/1,000 TN, respectively) in study 1, whereas pitfall and Ugglan (Grahnab, Ekhaga Marieholm, Hillerstorp, Sweden) traps had negligible captures (<0.1 and 0.0 birds/1,000 TN, respectively) in 4 studies that used them. On 11 occasions capture rates in 1 stand on 1 day in study 1 ranged from 50.0–100.0 birds/1,000 TN. Despite relatively high capture rates of birds in Tomahawk and Sherman traps in 2 studies, the 6 other studies had limited avian captures in both these and all other trap types used. Variability in avian capture rates within trap types across studies makes it difficult to predict the time of year when and habitats where avian captures could occur. Therefore, researchers should be mindful of potential negative impacts of small-mammal trapping on avian aspects of research when designing interdisciplinary studies that include both avian and small-mammal components conducted simultaneously at the same sites.

Additional Habitat, Diet and Range Information for the White-footed Vole (Arborimus albipes)

Abstract Little is known about the natural history of the white-footed vole (Arborimus albipes). We present new information on habitat, diet and range of this mammal as a result of 13 captures in the southern Cascade Range of western Oregon. The study area represents a range extension for the species. White-footed vole encounters were correlated less with distance to water than with basal area and density of alder (Alnus rubra) and percent cover of hazel (Corylus cornuta v. californica). Association with hazel has not been reported previously. Analysis of white-footed vole fecal samples provided the first documentation of mycophagy in this species and of consumption of hazel pollen from unopened catkins. This latter information supports previous speculation that the white-footed vole is semi-arboreal and provides corroborating evidence for the observed correlation with hazel.