Trends in Passerine Abundance in Denali National Park and Preserve, Alaska from 1995–2025
Mizel JD, Schmidt JH, Hughey JB, McIntyre CL. 2026. Trends in Passerine Abundance in Denali National Park and Preserve, Alaska from 1995–2025. Science Report. NPS/SR—2026/421. National Park Service. Fort Collins, Colorado. https://doi.org/10.36967/2317771
Here, we assess trends in the relative abundance of six forest-adapted and six shrub-adapted passerines from point count data collected along the Denali Park Road from 1995–2025. We found pervasive, positive trends among forest-adapted passerines, suggesting conifer expansion as a primary driver of changes in abundance within this assemblage. We found weaker evidence of changes in abundance among shrub-adapted passerines with only fox sparrow and savannah sparrow showing strong evidence of declines. Notably, we found no evidence of increasing abundance in this assemblage despite the observed expansion of deciduous shrubs within our sampling frame. This is consistent with previous work in Denali showing a weak response by shrub-adapted passerines to shrub expansion, possibly due to suboptimal structural characteristics of the expanding shrub cover, such as shorter height and a relatively diffuse distribution. Trends for forest-adapted passerines in Denali differed strongly from those estimated at the broader Bird Conservation Region (BCR) scale from North American Breeding Bird Survey (BBS) data, likely reflecting differences in the vegetation gradients captured by the two sampling frames. Where the BCR-level trends were stable, the trends in Denali were strongly negative (American robin) or positive (Swainson’s thrush and varied thrush). Where the BCR-level trends were strongly negative, the trends in Denali were strongly positive (dark-eyed junco, ruby-crowned kinglet, and yellow-rumped warbler). The BBS effort in Alaska is concentrated in below-treeline areas within the central boreal belt whereas our sampling frame along the Denali Park Road traverses both treeline and shrubline, making its passerine trends more susceptible to the effects of expanding trees and shrubs.
- Type
- Published Report
- Authors
- Mizel, Jeremy; Schmidt, Joshua; Hughey, Jared; McIntyre, Carol
- Date of Issue
- 2026-04
- Publisher
- National Park Service
- DOI
- 10.36967/2317771
- Units
- DENA , NRSS
- Keywords
- Breeding Bird Survey, landbirds, shrub expansion, songbirds, treeline