Tidal-flow restoration provides little nesting habitat for a globally vulnerable saltmarsh bird

摘要

Tidal marshes are among the most threatened habitats on Earth because of their limited natural extent, a long history of human drainage and modification, and anticipated future sea-level rise. Tidal marshes also provide services to humans and support species of high conservation interest. Consequently, millions of dollars have been spent on tidal marsh restoration throughout North America. Southern New England has a long history of tidal marsh restorations, often focused on removal of the invasive plant Phragmites australis. Working in 18 Connecticut marshes, we examined the bird community in 21 plots in restoration sites and 19 plots in reference sites. Restoration plots were divided into those in marshes where management involved restoring tidal flow and those where direct Phragmites control (e.g. cutting, herbicide) was used. Saltmarsh sparrows Ammodramus caudacutus, which are considered globally vulnerable to extinction, were less common where tidal flow had been restored than at reference sites and nested in only one of 14 tidal-flow restoration plots. No abundance differences were found for large wading birds, willets Tringa semipalmata, or seaside sparrows Ammodramus maritimus. Vegetation at sites where tidal flow had been restored showed characteristics typical of lower-elevation marsh, which is unsuitable for nesting saltmarsh sparrows. We conclude that, although tidal-flow restorations in Connecticut control Phragmites and restore native saltmarsh vegetation, they produce conditions that are largely unsuitable for one of the highest conservation priority species found in eastern U.S. salt marshes.