METHODS 



Tobalske collected field data on bird populations 

 and vegetation characteristics for this study. Our 

 statistical analysis was selected to quantify differ- 

 ences among stand conditions in the study area. 



Design 



During the 1989 and 1990 breeding seasons, bird 

 populations were censused with fixed-point counts 

 109 yards (100 m) in radius. Species detections 

 were by sight or sound, including birds in flight over 

 the plot. During both years, each point was visited 

 on three evenly spaced days between June 1 and 

 July 7. Counts were done between one-half hour 

 after sunrise and 10 a.m., for a period of 10 minutes 

 each. 



Count points were located with a coordinate grid 

 overlay placed on figure 2. After scaling distances 

 between lines on the grid to be 218 yards (200 m) 

 apart on the ground and numbering the points of 

 intersection sequentially, a random-numbers table 

 was read to select 10 points within each of three 

 stand conditions: clearcut, partial-cut, and unlogged 

 forest. Points were selected so that the radius of the 

 plot would not intersect another stand condition. 

 These points defined the census plots on the ground; 

 each was marked at the center with a survey flag. 



Because the CRNA (fig. 2) was difficult to map 

 accurately, a different method was used there to 

 select census points. Beginning at the southwest 

 corner of the natural area stand, a random number 

 was generated with a pocket calculator to determine 

 a compass bearing. After following this bearing for 



273 yards (250 m), a census plot was centered at the 

 destination. Subsequent plots were selected in the 

 same manner with a new bearing for all 10 points. 

 Bearings that would carry a plot within 109 yards 

 (100 m) of the boundary of the natural area were 

 ignored by returning to the origin and taking a new 

 bearing. 



Vegetation was sampled once per year during 

 July 1989 and 1990 at the 10 points in each stand 

 condition that were selected for bird censusing 

 (table 1). Sampling followed the guidelines of the 

 Ocular Method in Hahn and Jensen (1987) using 

 the General Plot Data and Ocular Plant Species 

 Data forms. Each plot had a 37-ft (11-m) radius, 

 with one plot at the center of each bird-count point. 

 Snags were included in all tree measurements. 

 Tree basal area was estimated with a "Relascope" 

 prism, and average dominant tree d.b.h. was deter- 

 mined through diameter-tape measurements 

 of five trees, or the maximum number lefl standing 

 if fewer than five. Percentage of cover was mea- 

 sured for trees, shrubs, graminoids, and forbs, using 

 horizontal estimates of the vertical projection of 

 each life form. Tree and shrub cover was further 

 sampled at three height categories: pole and larger, 

 sapling, and seedling tree classes, and tall, mid, and 

 low shrub classes. 



Analysis 



The mean count per point for each bird species 

 censused in 1989 and 1990 was calculated by 

 averaging data for the three yearly visits to each 

 point, giving 10 average counts for each bird 



Table 1 — Estimates of vegetation components within each of the four stand conditions at the Terrace Hill study 

 area and adjacent Coram Research Natural Area, Coram Experimental Forest, in 1989 and 1990 



Stand condition 



Clear- 



Partial- 



Unlogged 



Natural 



Proba- 



Vegetation component cut^ 



cut^ 



forest 



area 



bility2 



Tree basal area (ft^/acre) 8* 



35* 



104^ 



112^ 



0.001 



Tree d.b.h. of dominant tree (inches) 4* 



7* 



I4B 



15^ 



.001 



Tree total cover (percent) 3* 



24B 



59c 



63° 



.001 



Pole and larger (percent) 1* 



18^ 



44c 



48° 



.001 



Sapling (percent) 1* 



5* 



13^ 



13^ 



.001 



Seedling (percent 1 



2 



2 



2 



1.000 



Shrub total cover (percent) 13* 



379 



47B 



44B 



.006 



TalP (percent) 1* 



gAB 



IOAB 



13^ 



.016 



Mid3(percent) 10 



22 



25 



18 



.192 



Low^(percent) 2* 



gAB 





12^ 



.016 



Graminoid total cover (percent) 9 



11 



6 



4 



1.000 



Forb total cover (percent) 22 



18 



35 



42 



.032 



^Tree snags of all species and living paper birch trees were left standing where possible. 



^Low probability values indicate significantly different means among stand conditions, Bonferroni adjusted to control for 

 experimentwise error (SPSS Inc. 1983); superscript letters group similar means for each vegetation component. 

 ^Tall shrub, >10 ft (3 m); midshrub, 2 to 10 ft (0.6 to 3 m); low shrub, <2 ft (0.6 m) (Hahn and Jensen 1987). 



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