Divergence in Avian Communities Following Woody Plant Invasions in a Pine Barrens Ecosystem

We compared avian communities and vegetation characteristics in invaded and uninvaded pine barren ecosystems to test whether invasive woody plants were altering native bird communities. We hypothesized that structural changes in vegetation caused by the invasion of fire-intolerant deciduous trees were altering bird communities in the Albany Pine Bush, east central New York State. We recorded bird calls at 55 stations during breeding season to estimate abundances of breeding birds in areas dominated by fire-dependent pine-shrub savanna and areas dominated by invasive hardwoods (black locust, Robinia pseudoacacia, and aspens, Populus tremuloides and P. grandidentata). Vegetation surveys were conducted surrounding each station to quantify woody plant composition and structure. Sites characterized as invaded had more vegetation layers, twice as much closed canopy, and higher tree stem densities in all but the largest (> 25 cm dia) size classes. Forty-seven bird species were recorded; thirty-three at both invaded and uninvaded sites. Grassland/shrubland birds, such as prairie warbler (Dendroica discolor), field sparrow (Spizella pusilla), red-breasted nuthatch (Sitta canadensis), and eastern towhee (Pipilo erythrophthalmus), were twice as frequent and three times as abundant at uninvaded sites. Native bird species characteristic of closed-canopy forest were more frequent and abundant at stations in invaded sites. Multivariate analyses indicate distinct associations of particular birds with unique combinations of vegetation characteristics that differed between invaded and uninvaded points. A campaign of adaptive fire management holds promise to restore critical avian habitat in protected areas of this threatened barrens ecosystem.