Miller and Ralph 



Chapter 20 



Inland Habitat Relationships in California 



The logistic regression model included density of old- 

 growth (dominant and co-dominant) tree cover, tree species, 

 and stand size as variables explaining the differences between 

 sites with no detections and those with murrelets present 

 (table 2). Stands with higher density classifications, and 

 with redwood as the dominant tree species, were more likely 

 to have murrelets present. Results also indicated a very 

 minor effect of smaller stands increasing the likelihood of 

 murrelet presence. We found, however, no significant effect 

 of stand size on the status of murrelets in the stands 

 (Undetected, Present, or Occupied), when tested by Chi- 

 square contingency table (df= 6, % 2 = 3.294, P = 0.7721) 

 (table 4). Using these variables accounts for virtually all of 

 the variability in the model. 



For stands with a status of Occupied (n = 37), compared 

 with all Unoccupied stands (n =115), old-growth tree density 

 and tree species were significant variables (table 3) for 

 predicting observations of occupied behaviors. Stands in 

 higher density classes with redwood as the dominant species 

 were more likely to be classified as Occupied. 



Among stands with murrelet detections (n = 62), we 

 found no differences in habitat variables between stands 

 with a status of Occupied (n = 37) and Present (n = 25). 



Park Study: Large Contiguous Stands 



Central California 



Big Basin Redwoods State Park was surveyed in a matrix 

 of 37 survey stations. The elevation ranged from 240-500 m 

 and we divided stations into four equal categories (table 5). 

 We found the mean detection levels and the number of 

 Occupied stations higher for stations in lower elevation 

 categories. The proportion of Occupied stations was not 

 significantly different (P > 0.05) among topography categories 

 (table 5). Occupied behaviors were observed in all topography 

 categories, and the only station with a status of Undetected 

 was on a major ridge. 



Table 2 Results of logistic regression analysis for stands in California (n = 

 152) with a status of murrelets Present (Present and Occupied) (a = 62) and 

 Undetected (a = 90). Only variables with significant contribution to the 

 model are presented 



'Coast redwood (Sequoia sempervirens) or Douglas-fir (Pseudotsuga 

 menziesii) >50 percent of stand. 



2 Percent dominant and codominant tree cover. 



Table 3 Results of logistic regression analysis for stands in California 

 (n = 752; with status of Occupied (n = 37) and stands with murrelets Present 

 or Undetected (UnoccupiedXn = 115). Only variables with significant 

 contribution to the model are presented 



'Coast redwood (Sequoia sempervirens) or Douglas-fir (Psuedotsuga 

 menziesii) >50% of stand. 



2 Percent dominant and codominant tree cover. 



Northern California 



We surveyed 352 stations in the 8 stands within northern 

 California parks. We found that topography had a major 

 influence on murrelet use (P < 0.0001). The mean detection 

 levels were three times higher in major drainages (table 6) 

 than on the major ridges. 



Table 4 Percent of stands by murrelet use or status in each size category of stands surveyed in California for 

 the Stand Study. Stands with a designation of Present had murrelet detections, but no observations of below 

 canopy, or Occupied behaviors 



Totals 



152 



90 



59.2 



16.4 



37 



24.3 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



211 



