Breeding Bird Responses to 

 Diameter-Cut Logging in 

 West-Central Idaho 



Dean E. S¥Sedini 



INTRODUCTION 



The structure of forest vegetation is an important bird 

 niche dimension (Anderson and Shugart 1974; Conner 

 and others 1983; James 1971; Karr and Roth 1971; 

 MacArthur 1964; Morrison and Meslow 1983b; Willson 

 1974). Alterations in structure caused by logging pro- 

 duce changes in the organization of associated bird 

 communities (Blake 1982; Conner and Adkisson 1975; 

 DeByle 1981; Franzreb and Ohmart 1978; Hagar 1960; 

 Kilgore 1971; Maurer and others 1981; Morrison and 

 Meslow 1983a; Scott and Gottfried 1983; Strelke and 

 Dickson 1980; Szaro and Balda 1979; Titterington and 

 others 1979; Webb and others 1977). 



Diameter-cut logging is the removal of all 

 merchantable trees above a specified diameter breast 

 height (d.b.h.)(Ford-Robertson 1971). This study exam- 

 ined relationships between breeding birds and a 

 commercial diameter-cut in a Douglas-fir forest in west- 

 central Idaho. The objective was to quantitatively assess 

 the effects of the logging on breeding bird populations 

 and community organization. All tree stems greater than 

 10 inches (25 cm) d.b.h. were felled within defined 

 cutting units. Logging began in September and was 

 completed in November 1976. 



STUDY AREA 



The study was made on two forested experimental 

 watersheds in the Silver Creek drainage, a tributary of 

 the Middle Fork of the Payette River. The area is about 

 56 miles (90 km) northeast of Boise in Valley County, 

 ID. Watershed SC-6, about 403 acres (163 ha) in size, 

 was partially logged in three separate blocks; watershed 

 SC-3, about 319 acres (129 ha), served as an unlogged 

 control. 



Watershed slopes are steep, dissected, and face 

 southeast. Soils are weakly developed and underlain by 

 granitic bedrock. Annual precipitation in the area 

 averages about 32 inches (80 cm); a large portion occurs 

 as snowfall (Megahan and Clayton 1983). 



Douglas-fir (Pseudotsuga menziesii var. glauca) and 

 ponderosa pine (Pinus ponderosa) are the dominant 

 overstory trees, with scattered stands of grand fir (Abies 

 grandis), lodgepole pine (Pinus contorta), and Engelmann 

 spruce (Picea engelmannii). Mallow ninebark 

 (Physocarpus malvaceous) and white spiraea (Spiraea 

 betulifolia) normally dominate the shrubby undergrowth, 

 but Scouler willow (Sali.x scouleriana). Rocky Mountain 



maple (Acer glabrum), snowberry (Symphoricarpos spp.) 

 and common chokecherry (Prunus virginiana) are often 

 present. Many forbs and graminoids occupy the ground 

 layer. 



Two habitat types (Steele and others 1981) are mainly 

 represented: Douglas-fir/ninebark, ponderosa pine phase, 

 and Douglas-fir/white spiraea, ponderosa pine phase. 



LOGGING PROCEDURE 



Trees on watershed SC-6 were cut commercially to a 

 10-inch (25-cm) minimum diameter (breast height) in 

 three separate and well-spaced cutting units (fig. 1). The 

 units, topographically defined and irregularly elongate in 

 outline, were 20, 22, and 45 acres (8, 9, and 18 ha). 

 Uncut buffer strips bordered the cutting units, 

 averaging 50 ft (15 m) to first- or second-order stream 

 channels, and 100 ft (30 m) to the third-order (main) 

 stream channel. All cutting units were on southerly 

 aspects. Logs were yarded by helicopter to minimize site 

 damage. Slash was lopped, scattered, and then broadcast 

 burned. An estimated 80 percent of the slash was 

 effectively burned. 



STUDY METHODS 



Two 20-acre (8-ha) study plots were established on 

 watershed SC-6 before logging; plot 1 was located within 

 the largest cutting unit; plot 2 was located within the 

 smallest unit. A third 20-acre (8-ha) study plot was 

 established on watershed SC-3 to serve as an unlogged 

 control. Birds were censused and otherwise studied each 

 year on all three of the study plots beginning in 1976 

 (prelogging) and ending in 1979 (third-year postlogging). 

 Overstory (tree) vegetation was sampled on the cutting 

 units before logging in 1976 and after logging in 1977. 

 Understory vegetation (shrubs, forbs, graminoids) was 

 sampled in 1976 (prelogging) and variously thereafter 

 until 1981 (fifth-year postlogging). 



Overstory Vegetation 



Overstory vegetation data and methodology are from 

 Geier-Hayes and Ryker (1983). A surveyed and marked 

 650- by 650-ft (200- by 200-m) grid system was 

 superimposed on the experimental watersheds. Grid 

 coordinates were used to permanently reference sampling 

 locations. Nine sample points, each equidistant from the 

 other, were located in each grid square. Overstory data 

 were derived from sample points that were located 

 within cutting unit boundaries. 



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