Classifying and Photographing Habitat at Breeding Bird Survey (BBS) Point Count Locations Throughout the Sierra Nevada

The Breeding Bird Survey (BBS) is an annual, volunteer-based point count survey coordinated by the Biological Resources Division of the USGS and the Canadian Wildlife Service. The survey consists of a continent-wide array of roadside point count transects, or routes. Each route is 24.5 miles long, and comprises 50 point counts at 0.5 mile intervals. Expert volunteer observers conduct point counts once each year during the peak of the breeding season, recording numbers of every species detected within a quarter mile radius. BBS data provide the most extensive, long-term data set available on landbird population trends, and are therefore tremendously valuable for conservation planning.

Despite the clear value of the BBS, at least two factors presently limit the survey's usefulness for monitoring changes in bird populations across the Sierra Nevada bioregion:

• In most analyses of BBS data, the route, rather than the individual point, has been treated as the unit of analysis; trends for particular species are calculated according to cumulative results from all 50 points along a route. Twenty-five mile long routes nevertheless often cross multiple major habitat types. This broad-brush habitat approach cannot be improved upon until reliable, ground-truthed habitat data exist for individual point count locations.
  
  
• BBS point counts are conducted exclusively at roadsides, which often include a large proportion of fragmented and edge habitats, and may poorly represent the larger landscape. This focus on roadside habitats surely biases resulting descriptions of avian community composition, by over-counting species associated with roadside habitats, and under-counting species associated with habitats that are poorly represented along roadsides. Moreover, abundance trends for many species may actually differ by habitat, such that the non-representative nature of route locations actually biases trend information, as well as descriptions of community composition.
  

To address these problems in the Sierra, we are collaborating with USDA Forest Service personnel to produce ground-based habitat descriptions and collect archival photographs at each of the 50 counting stations along all of the 48 BBS routes that lie partly or entirely within the Sierra Nevada's national forests. Classifying and photographing the habitat at these 2,400 points will fulfill multiple goals:

• By determining which habitats are or are not well sampled by the BBS, we can facilitate the improvement of avian monitoring efforts throughout the Sierra's national forests. A detailed understanding of which habitats are currently well sampled or poorly sampled by the BBS (in relation to the habitat makeup of the larger landscape) will allow future monitoring efforts to focus scarce resources on those habitats most in need of monitoring.
  
  
• Meaningful interpretation of BBS results requires more detailed information about the particular habitats being sampled. Habitat classifications for each point will facilitate habitat-specific analyses of BBS results, and may even allow analysis of habitat-specific trend data.
  
  
• Our archival digital photographs will serve as benchmarks for assessing future ecological change througout the Sierra.

2002 crew members Mariely Morales and Jeff Firman.

For more information, contact Rodney Siegel.

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