O'Donnell 



Chapter 14 



Effects of Station Placement and Observer Bias 



ABOVE CANOPY ACTIVITES 

 D BELOW CANOPY ACTIVITIES 



O 



o 



35- 

 30 - 



B 



D 



Figure 1 Relationship between percent of open sky at survey stations and 

 observations of marbled murrelets flying above and below the canopy. Data from 

 nine sites in northwestern California. 



detected murrelets by sound at greater distances from stations 

 placed in open meadow, than at stations closely surrounded 

 by forest, accounting for difference in numbers of detections 

 between sites. Detection distances for murrelets that were 

 heard and not seen varied considerably between sites in 

 northwestern California (O'Donnell, unpubl. data). The 

 locations of stations ranged from closed canopy forest to 

 large, open prairies. The maximum detection distances at 

 stations in more open areas was generally greater than for 

 stations within the forest. 



Discussion 



Observer Variability 



There can be little doubt that variability exists between 

 observers in their ability to see and hear murrelets. While 

 some differences between observers cannot be eliminated, 

 adequate training and evaluation can greatly improve 

 individual abilities and increase comparability between 

 observers. A training and evaluation protocol (Ralph and 

 others 1993) was developed to accomplish this goal. The 

 training program helps trainees to develop their ability to 

 detect murrelets in the forest and to accurately record 

 observations according to protocol. The evaluation, a 

 simultaneous survey conducted by trainees and a qualified 



evaluator, insures that trainees are able to survey murrelets 

 at acceptable levels of proficiency. In California, Oregon, 

 and Washington, all persons conducting murrelet surveys 

 for management or research purposes must successfully 

 complete an evaluation process. Since inception of the training 

 and evaluation program in 1991, approximately 500 persons 

 have been evaluated in California alone (Burkett, pers. comm.), 

 providing a large pool of qualified observers. 



Site Characteristics 



Factors influencing an observer's ability to hear and see 

 murrelets can largely be controlled by sensible placement of 

 survey stations. Because such a high proportion of murrelets 

 are detected by call alone, survey stations should not be 

 placed near sources of loud noise. Similarly, since behaviors 

 suggestive of breeding activity are determined primarily 

 from visual observations of murrelets, it is important to 

 place survey stations in areas that have the greatest view of 

 open sky (Ralph and others 1993). 



Acknowledgments 



I thank Steve Courtney, Dave Forma, Debbie Kristan, S. 

 Kim Nelson, Peter Paton, C. John Ralph, and Sherri Miller 

 for comments on this manuscript. 



140 



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



