Impacts of oil and gas development on wintering grassland birds at Padre Island National Seashore, Texas

摘要

Padre Island National Seashore provides important habitat for declining wintering grassland birds, yet oil and gas development is widespread in the Park. Our objective was to evaluate the effects of resource extraction on the wintering grassland birds of the Park. In January-March 2007 and 2008, we surveyed 5 active and 4 abandoned well sites and 4 road sites to investigate the relationship between distance from disturbance (well pads, access roads) and bird abundance. At road sites, bird abundance was positively correlated with increased distance from road edge, but we found no linear relationship at active or abandoned well sites. However, mean bird abundance in the first (0-30 m) distance interval of active well transects was less than half that at the second interval, and was the lowest value for all active intervals except the ninth. First-interval abundance at active wells was lower than abundance at any abandoned well interval. Road transects likewise showed low abundance in the initial interval, although unlike at active wells, abundance increased steadily with distance from the center of disturbance. This trend of lower overall numbers at the first interval of active well transects was driven largely by Sturnella magna (Eastern Meadowlark) and S. neglecta (Western Meadowlark). A combination of high noise levels near active well pads and lack of tall vegetation from which to sing may have contributed to low numbers of meadowlarks, which were the only birds to sing regularly during the study period. We recommend: (1) reducing noise at active sites, (2) limiting vegetation disturbance near pads and roads, (3) maintaining existing perch sites, and (4) limiting road construction.