Impact of the spread ofPhragmites on the distribution of birds in Connecticut tidal marshes

Abstract

Dense monocultures ofPhragmites australis (common reed) have been rapidly expanding in Connecticut’s tidal wetlands at the expense of cordgrass (Spartina spp.) and cattail (Typha spp). Bird and vegetation surveys in 40 salt and brackish marshes showed that there were significantly fewer species of birds and state-listed species inPhragmites-dominated wetlands than in short-grass marshes. Seaside Sparrow. Saltmarsh Sharp-tailed Sparrow, and Willet, three marsh specialists adapted to nesting in short graminoids, had low frequencies in plots dominated byPhragmites. Marsh Wren and Swamp Sparrow, however, are marsh specialists that prefer tall, reedy vegetation, and both species had significantly greater densities at sites with morePhragmites or cattail. Although the bird communities of cattail sites andPhragmites sites were similar, the abundance of Virginia Rails was positively correlated with percent cover of cattail but notPhragmites. The extent of pools was positively related to bird species richness in short-grass meadows but not inPhragmites plots. InPhragmites-dominated wetlands, the height and density of reed stands may inhibit bird use of any pools that are present. Muskrats create pools that may enhance bird species richness, but populations of this mammal have dwindled during the same time period thatPhragmites increased in connecticut’s marshes. Although a few species may benefit from reed invasion, it has a negative impact on some marsh bird species that have already declined. These findings support the continued need for marsh restoration and the control of common reed.