Growth of two Atlantic Coast Piping Plover populations

Species listed under the U.S. Endangered Species Act are required to meet stated recovery goals for delisting. These goals often are developed early in the species' conservation history and may need to be updated or refined as new information becomes available. The Atlantic Coast Piping Plover (Charadrius melodus), which was listed more than 30 yr ago, has not met recovery goals through much of its range. Initial recovery goals included maintaining a reproductive output of 1.5 fledged chicks per pair for 5 yr. This goal was based on modelling that assumed equal survival rates for adults throughout the range, but recent studies suggest that demographic rates may vary with latitude. To investigate latitudinal variation, we developed demographic and population growth estimates for 2 breeding populations of Piping Plovers on the U.S. Atlantic Coast on Fire Island, New York (40.7°N), and on the Outer Banks of North Carolina (35.3°N) in 2013–2017. Breeding success (nest success and pre-fledge chick survival) varied annually but was lower in North Carolina than New York. Average adult true survival in New York (= 0.73, SE = 0.04) was similar to average survival in North Carolina (= 0.69, SE = 0.07). Annual post-fledging survival for both sites, however, was variable and often higher than had been previously reported for Atlantic Coast Piping Plovers (0.43–0.66 for New York; 0.31 and 1.0 for North Carolina). While the estimated reproductive output needed for a stationary population for both sites was similar (1.10 chicks per pair for New York, 95% CI: 0.83–1.41; 1.08 for North Carolina, 95% CI: 0.67–1.59), only the New York population achieved or exceeded these values during our study. Our findings suggest that understanding annual and latitudinal demographic variability would be helpful in refining recovery goals.