Landbird inventory for Mount Rainier National Park (2003-2004)

Wilkerson, Robert; Siegel, Rodney; Schaberl, Jim

The NPS established the Natural Resource Inventory and Monitoring Program (I&M) to help park units collect scientifically credible ecological resource information and to develop or improve field and analytical monitoring techniques. As a first step, 5-year inventories were initiated in the North Coast and Cascades Network (NCCN) to gather core sets of data describing park vascular plants and vertebrate resources. In 2003 The Institute for Bird Populations (IBP) collaborated with personnel at Mount Rainier National Park to initiate a two-year, park-wide, inventory of landbirds. The broad goals of the inventory were to elucidate spatial patterns of abundance across the park for a large suite of species, and to produce information that will assist park managers and cooperators in designing the park‘s long-term landbird monitoring program.During our two field seasons (2003 and 2004), we counted 6,026 individual birds during 969 point counts conducted along 134 transects. Transects were well distributed across the park. We documented 95 bird species (including the Hermit-Townsend‘s Warbler hybrid) in the park during the field season. Seventy-eight of these species were detected during at least one point count, while the remaining 17 were recorded as incidental observations only at times other than during point counts. We also conducted detailed habitat assessments at each of the 969 survey points. We present 'naïve' habitat-specific density estimates, unadjusted for differences in detectability, for all 78 species recorded during point counts. We also present habitat-specific density estimates, adjusted for species- and habitat-specific differences in detectability, for 45 species that were detected at least five times during point counts, as well as lists of all species detected in each of 17 habitats we sampled in the park. Although the results were rarely found to be statistically significant, we rank habitats with regard to a) the number of species detected in each (species richness) and b) the overall density of birds (all species pooled) estimated to occur in each, and find some substantial and perhaps surprising differences across park habitats. In particular, the two lowest elevation habitats harboring deciduous tree components ranked first (10.65 birds/ha—Conifer Deciduous Mix) and third (8.55 birds/ha—Red Alder) in overall density of birds. The three major mid- and high-elevation forest types all ranked higher than the three major low- to mid-elevation forest types in overall density of birds. Mid- to high-elevation forest types include Pacific Silver Fir (7.82 birds/ha), Subalpine Fir (7.31 birds/ha), and Mountain Hemlock (7.00 birds/ha). Mid- to low-elevation forest types include Douglas-fir (6.53 birds/ha), Mixed Douglas-fir/Western Hemlock (6.48 birds/ha), and Western Hemlock (6.35 birds/ha). Surprisingly, the two shrub habitats ranked among the lowest four habitats, with Mid-elevation Shrub at 4.88 birds/ha and High-elevation Shrub at 4.79 birds/ha. Park-wide bird density (all species pooled) was lower at Mount Rainier (6.2 birds/point) than both North Cascades (7.6 birds/point) and Olympic (6.6 birds/point). When pooled bird density is examined across shared habitats, Mount Rainier is lower when compared to North Cascades but is slightly higher than at Olympic in 8 of 10 habitats. The difference between Mount Rainier and Olympic in pooled bird density is noticeable in higher elevation habitats, with Mount Rainier having a density of 1.16 more individuals/ha than Olympic.

Landbird inventory for Mount Rainier National Park (2003-2004)

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