Importance & Issues
Populations of many common and rare bird species in the Pacific Northwest are believed to be declining. Besides being important in their own right, landbirds are an important ecosystem component (e.g., providing seed dispersal and insect control) and are good indicators of the effects of local and regional changes in ecosystems. We use robust scientific methods to assess which species have declining, stable, or increasing populations in the North Coast and Cascades Network parks. Where possible, we formulate and evaluate hypotheses about causes of population change.
- Lewis & Clark National Historical Park
- Mount Rainier National Park
- North Cascades National Park Complex
- Olympic National Park
- San Juan Island National Historical Park
Our primary objective is to detect trends in the density of as many landbird species (including passerines, near-passerines, and galliformes) as possible throughout accessible areas of five North Coast and Cascades Network parks during the breeding season. As a secondary objective, the data we collect allow us to track changes in the breeding season distribution of birds throughout the parks, which may occur in response to climate change.
We monitor park bird populations by conducting annual counts of all bird species heard or seen during a seven-minute survey at over 1,000 sampling locations across the parks. The sample design for the three large parks (Mount Rainier, North Cascades, and Olympic National Parks) uses six panels of point-count transects (each comprising approximately 14 count stations) in each park.
At North Cascades and Olympic National Parks, each panel includes four low-elevation transects (transect starting points <650 m), four mid-elevation transects (transect starting points between 650 m and 1,350 m) and four high-elevation transects (transect starting points >1,350 m). At Mount Rainier National Park, the sample design is the same as at the other two large parks, except there are only two low-elevation transects in each panel, and the cutoff between low-elevation transects and mid-elevation transects is 800 m rather than 650 m. All transects start at points on park roads or trails and then extend perpendicularly (or as close to perpendicularly as topographic and physiographic features allow) in both directions away from the trail or road.
At the two smaller parks, Lewis and Clark National Historical Park and San Juan Island National Historical Park, rather than using transects, we survey birds in alternating years at count stations arrayed in regular grids that are distributed across the entire park.
At all parks, we use distance sampling to estimate detection probability and account for birds that may be present but undetected at count stations.
- Number of species detected
- Number of exotic species detected
- Number of Partners in Flight priority species detected
- Species frequency of occurrence (percent of point count stations where a species was detected) and density (individuals per hectare, by species) during the breeding season.
Parks in our Network can fill vital roles as both refuges for bird species dependent on late-successional forests and as reference sites for assessing the effects of land-use and land-cover changes on bird populations throughout the Pacific Northwest region. These changes may result from regional activities such as land conversion and forest management, or from broader-scale processes such as climate change.
Monitoring population trends at reference sites in national parks is important because parks are among the few areas in the United States where population trends due to large-scale regional or global change patterns are minimally confounded with local changes in land use. Results of long-term monitoring of landbirds in the North Coast and Cascades Network will also inform future management decisions in the parks, including those related to visitor impacts, fire management, and the effects of introduced species.