Impact of reed harvesting and Smooth Cordgrass Spartina alterniflora invasion on nesting Reed Parrotbill Paradoxornis heudei

摘要

The Reed Parrotbill Paradoxornis heudei is an endemic reedbed-inhabiting passerine of east Asia. In the Shanghai municipality, which harbours significant populations of this species, almost all reedbed surfaces are annually harvested. Furthermore, the reedbeds are being invaded by Smooth Cordgrass Spartina alterniflora, an introduced species that can outcompete the native Common Reed Phragmites australis. In this paper, we have shown that Reed Parrotbills do not nest in areas dominated by Smooth Cordgrass and avoid using them. In the areas that are primarily composed of Common Reed, the densities of birds are higher in the unharvested sections. The birds appear to select nesting sites with low Smooth Cordgrass densities, tall reed stems, and relatively equal densities of both dry and green stems. Reed harvesting activity results in vegetation that is too low for bird nesting. However, no nests were found in areas where the reeds had not been harvested for several years and had high densities of dry reed stems; these results could be attributed to the fact that the high density of broken stems reduced the vegetation cover. On the basis of our results, we recommend implementation of four years harvesting-cycle rotation and avoidance of reclamation in reedbeds which have not been invaded by Smooth Cordgrass.