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

Dense monocultures of Phragmites 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 in Phragmites-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 by Phragmites. Marsh Wren and Swamp Sparrow, however, are marsh specialists that prefer tall, reedy vegetation, and both species had significantly greater densities at sites with more Phragmites or cattail. Although the bird communities of cattail sites and Phragmites sites were similar, the abundance of Virginia Rails was positively correlated with percent cover of cattail but not Phragmites. The extent of pools was positively related to bird species richness in short-grass meadows but not in Phragmites plots. In Phragmites-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 that Phragmites 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.