Long Term Progress in Riparian Restoration with Concurrent Avian Declines in the Southern San Francisco Bay Area (CA)

ABSTRACT

The restoration of riparian habitats aims to provide habitat for birds and other environmental benefits; yet the evaluation of long-term outcomes is rare. To address this knowledge gap, we used bird and vegetation data from Coyote Creek Field Station (CCFS), in the southern San Francisco Bay Area, to assess the progress of two riparian revegetation projects (1987 Revegetation, 1993 Revegetation) over nearly two decades. Restoration success was measured by changes in 1) vegetation structure and composition, and 2) avian abundance, diversity, and community composition. We compared the two revegetated areas to a remnant riparian reference site and a managed floodplain overflow channel in three time periods (1996–1998, 2004–2006, 2012–2014) using ANOVA, Tukey’s HSD tests, and beta diversity analysis of avian community composition. Over time, the restored areas became more similar to the remnant riparian reference site in four of seven indices. The avian community became more similar across the habitat areas over time, although differences remained. Migratory birds declined across all habitat areas, while resident and wintering birds declined in one revegetated habitat only. Overall we found that different types of data told different stories, indicating both convergence with the reference site and ongoing differences. Our findings highlight the need for multifaceted approaches to evaluating restoration success.