Treesearch

Studies of the foraging behaviors of birds have been largely descriptive and comparative. One might then expect studies with similar objectives to have similar study designs but that is not the case. Papers in this symposium that focused specifically on study design contain a diversity of biological perspectives. Similarly, there is no accord among statisticians on experimental design and data analysis of multivariable systems. Further, biological and statistical considerations in study design are not always in agreement.

We examined the relationship between nest site availability and density of secondary cavitynesting birds by blocking cavities in an oak-pine (Quercus spp.-Pinus sp. ) woodland. In 1986 and 1987we blocked 67 and 106 cavities, respectively, on a 37-ha plot. The combined density of secondary cavity-nesting birds did not decline in either year by a greater proportion on the treatment plot than on a control plot, indicating that cavities were not limiting. In habitats where timber management has not substantially reduced availability of natural cavities, managers should not assume nest site...

The foraging characteristics of Hammond’s and Western flycatchers in northwestern California varied with different stages of the breeding cycle during the breeding seasons (early April-mid August) in 1984 and 1985. The species’ behaviors did not always vary in parallel nor were all foraging behaviors distributed equally during the breeding cycle. For example, the direction of aerial foraging movements for both species did not differ between stages, In contrast, the predominant type of foraging activity (either hover-glean or flycatch) differed by stage of the breeding cycle for Western...

Abstract - In-stream water quality regulations of California state that silvicultural disturbances must not increase turbidity levels more than 20 percent above naturally occurring background levels. These regulations fail to take into account the natural variation of turbidity and suspended sediment concentration along a short stretch of an undisturbed stream. At Janes Creek and Miller Creek in northwestern California, natural variations in turbidity and suspended sediment concentration along stream reaches of 292.6 and 110.6 meters were -.015 to 3.73 times that of the 20 percent man-induc...

Abstract - The risk of debris slides resulting from logging must often be appraised by foresters planning timber harvests. The Board of Forestry of the State of California commissioned the development of a Mass Movement Checklist to guide foresters making such appraisals. The classification accuracy of the Checklist, tested using 50 logging-related debris slides and 50 logged sites that had not produced debris slides, was correct at 60 sites in northwestern California. Its low accuracy is attributed to low variability of several constituent variables. Although the Checklist may be useful...

Ponderosa pine, Jeffrey pine, mixed conifer, and white fir forests of the Cascade and Sierra Nevada Ranges of California have been important resources and were extensively altered by timber harvest between 1850 and 1950. Many historical logging operations were small in size and of short duration. Other operations encompassed thousands of acres and existed for relatively long periods of time. Before settlement of California by Europeans, there were extensive forests in the Cascade and Sierra Nevada Ranges of California, much of it suitable for timber production. The forests were dominated...

Fire managers of southern California chaparral often assume that the amount of dead material in chaparral shrubs is closely related to canopy age. Analysis of chamise (Adenostoma fasciculatum), sampled from southern California shrublands, indicates that the ratio of dead to live components is not related reliably to age of shrub canopy. Further statistical description of the data indicates that fractions of dead material greater than 0.40 are rare. The results provide grounds for seriously questioning current assumptions about the strong relationship between age and fraction dead in...

Nearly 70 years of research and application are reviewed and assessed. Results of direct control projects can be characterized as generally effective, temporary, quite variable, and unpredictable in reducing subsequent tree mortality. Some causes of this characterization are variable and difficult stand conditions and logistics, lack of good beetle population measurements and prediction, unknown attributes of tree and stand dynamics and of beetle population dynamics, and unforeseen post-application factors. The control method used did not appreciably change this characterization: fell-peel-...