Managing individual nests promotes population recovery of a top predator

Threatened species are managed using diverse conservation tactics implemented at multiple scales ranging from protecting individuals, to populations, to entire species. Individual protection strives to promote recovery at the population- or species-level, although this is seldom evaluated. After decades of widespread declines, bald eagles, Haliaeetus leucocephalus, are recovering throughout their range due to legal protection and pesticide bans. However, like other raptors, their recovery remains threatened by human activities. Bald eagle nests are commonly managed using buffer zones to minimize human disturbance, but the benefits of this practice remain unquantified. Within Voyageurs National Park (VNP), Minnesota, USA, managers have monitored bald eagle populations for over 40 years, and since 1991, have protected at-risk nests from human disturbance using buffer zones (200 and 400 m radius). We aimed to (1) quantify the recovery of bald eagles in VNP (1973–2016), and (2) provide a first-ever evaluation of the individual- and population-level effects of managing individual nests. To do so, we developed Bayesian Integrated Population Models combining observations of nest occupancy and reproductive output (metrics commonly collected for raptors) to estimate nest-level probabilities of occupancy, nest success, and high productivity (producing ≥2 nestlings), as well as population-level estimates of abundance and growth. The breeding population of bald eagles at VNP increased steadily from <10 pairs in the late 1970s to 48 pairs by 2016. At the nest-level, management significantly improved occupancy and success. At the population-level, management led to 8% and 13% increases in nest success and productivity rates, respectively, resulting in a 37% increase in breeding pair abundance. Synthesis and applications. There is a clear need to evaluate how management approaches at multiple scales assist in species recovery. Our study uses an Integrated Population Model to reveal the population-level benefits of a widely used, individual-based management action (protecting nests using buffer zones) on a recovering raptor.