Effects of Oil and Gas Development on Waterfowl Nesting Ecology in the Bakken Formation of North Dakota

Abstract

The Prairie Pothole Region (PPR) is one of the most important areas on the continent for grassland-nesting birds. Thirty percent of the PPR overlaps the Bakken shale formation where rapidly accelerating oil and gas development has the potential to impact millions of breeding waterfowl. While oil and gas development has negatively affected other ground-nesting birds such as sagebrush passerines and Greater Sage-Grouse (Centrocercus urophasianus) in Wyoming, the potential impact on breeding waterfowl in the PPR is unknown. In addition, the PPR landscape is already heavily fragmented by agriculture, and increasing land conversion and disturbance from petroleum extraction may further exacerbate deleterious effects. The availability and quality of upland nesting habitat directly influences duck nest density and success, which have been shown to ultimately drive waterfowl populations. In this study, I located and monitored waterfowl nests in survey plots that were stratified by intensity of energy development as measured by the number of well pads within four square miles. Over three years, we systematically searched 8,657 hectares of grassland and monitored 4,774 duck nests. Blue-winged Teal (Spatula discors), Gadwall (Mareca strepera), and Mallard (Anas platyrhynchos) comprised 75% of nests. I used program MARK through the RMARK package to build models of nest survival based on ecological variables measured at local and landscape scales, as well as various metrics of oil and gas activity. Metrics included age of nest when found, nest initiation date, species, year, Robel pole measurement, distance to nearest active oil well, county road, and major road, active oil well intensity, and number of wells at various distances (from 500 to 4000 meters in 500-meter increments) from each nest. Typical metrics such as number of wells and roads did not negatively affect waterfowl nest success and my top-ranked model, major roads showed a positive relationship suggesting that nests closer to major highways have higher nest survival. Then, I investigated the effects of oil and gas development on nest density and area avoidance as estimated at two spatial scales: 1) a year-specific analysis of landscape-level density using survival-corrected nest densities calculated at the block level (four square miles) and 2) a within-replicate Monte-Carlo randomization analysis to evaluate used vs. available nest-site relationships in reference to locations of oil and gas activity at the replicate level (32 ha). Additional metrics included in the landscape-level density analysis were number of wetland basins, basin hectares, percent grassland within four square miles, and various