Forecasting Avian Responses to Elwha River Restoration

Abstract

Riparian restoration increasingly employs dam removal, but with limited knowledge about post-removal ecological impacts. Comprehensive ecological study has occurred on few dam removals and rarely on associated terrestrial components. Research supporting the Elwha River restoration program, Washington, USA, helps fill this gap as the largest dam removal project to date. We developed forecasts of avian responses to post-removal forest restoration in Elwha reservoirs. We modeled abundance patterns for 8 species using avian inventory data and habitat variables at local, patch, and landscape scales. We evaluated models using Akaike’s Information Criterion and determined the relative importance of each variable and scale using multi-model inference. Local habitat variables best explained abundance patterns for most species. We forecasted avian responses to forest restoration in the drained Lake Mills reservoir with and without conifers. Planting conifers hastened forecasted avian responses. Forecasts suggest birds associated with deciduous forests and edge habitats will colonize restored habitats rapidly, but birds associated with conifers may not respond markedly for more than a century. Birds can provide a measure of early restoration progress, but comprehensive restoration of Elwha avifauna will take longer than the dams have been in place. This conclusion echoes a familiar theme in Pacific Northwest forest restoration: anthropogenic impacts occur rapidly, but full restoration is comparatively slow.