Estimating the abundance of Long‐billed Curlews in Nebraska

ABSTRACT Long‐billed Curlews (Numenius americanus) are shorebirds of high conservation concern in North America. Populations have declined in the last 150 yr primarily due to habitat loss and conversion. We conducted a 2‐yr study to estimate the density and statewide abundance of breeding Long‐billed Curlews in Nebraska during 2008 and 2009. Surveys were conducted during the prenesting period in April when Long‐billed Curlews were likely to be detected. We used a simple random sample of roadside survey routes (N= 39), each consisting of 40 5‐min point‐counts at 800‐m intervals. We modeled detection probability and found that wind speed negatively affected detectability, but found no evidence of either year effects or observer bias. We estimated there were 0.0038 Long‐billed Curlews per hectare (0.38 Long‐billed Curlews per km²) along survey routes and, by extrapolation, estimated there were 23,909 (SE = 1685; 95% CI: 20,810—27,471) Long‐billed Curlews in Nebraska. Our population estimate suggests that ～15 to 22% of the United States population of Long‐billed Curlews is found in Nebraska. Curlews were not evenly distributed within our survey area, with the highest densities in the central Sandhills, an area dominated by grass‐stabilized sand dunes and shallow wetlands, and the lowest densities in predominantly agricultural areas. Because Long‐billed Curlews in Nebraska face many potential threats resulting from land‐use changes, monitoring of the breeding population should be continued. Our survey method was efficient and yielded interpretable results; other states or regions should consider adopting this approach for estimating curlew abundance.