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 winteringgrassland birds, which are declining throughout their breeding range, yet oil and gasdevelopment is widespread in the park. My objective was to evaluate the effects ofresource extraction on the park's grassland birds and make managementrecommendations based on my findings.In January-March 2007 and 2008, I surveyed 5 active, 4 abandoned, and 4 roadsites to investigate the relationship between distance from disturbance (well pads, accessroads) and bird abundance. I also compared abundance among the 3 site types. At eachsite I recorded bird numbers and species in 10-m distance bands along all transects (4transects/well, 2 transects/road), each extending 300 m from the road or pad.At road sites bird abundance was positively correlated with increased distancefrom road edge, but I found no linear relationship at active or abandoned well sites.However, mean bird abundance in the first (0-30-m) distance interval of active welltransects was less than half that at the second interval, and was the lowest value for allactive intervals except the ninth. First-interval abundance at active wells was lower thanabundance at any abandoned well interval. Road transects likewise showed lowabundance in the initial interval, although unlike at active wells abundance increasedsteadily with distance from the center of disturbance.This trend of lower overall numbers at the first interval of active well transectswas driven largely by 1 species, the meadowlark. A combination of high noise levelsnear active well pads (up to 80 dB) and lack of tall vegetation (on average 30% lower than the 60-90-m interval) from which to sing may have contributed to low numbers ofmeadowlarks, which were the only birds to sing regularly during my study period.While most birds appear to be minimally affected by resource extraction at PadreIsland, to ensure minimal impacts on sensitive species I recommend: 1) reducing noise atactive sites, 2) limiting disturbance to vegetation near pads and roads, 3) maintainingexisting perch sites, 4) restoring all vegetation to its pre-extraction condition, 5) limitingroad construction.