Predicting population responses to environmental conditions or management scenarios is a fundamental challenge for conservation. Proper consideration of demographic, environmental and parameter uncertainties is essential for projecting population trends and optimal conservation strategies. We developed a coupled integrated population model-Bayesian population viability analysis to assess the (1) impact of demographic rates (survival, fecundity, immigration) on past population dynamics; (2) population viability 10 years into the future; and (3) efficacy of possible management strategies for the federally endangered Great Lakes piping plover Charadrius melodus population. Our model synthesizes long-term population survey, nest monitoring and mark–resight data, while accounting for multiple sources of uncertainty. We incorporated latent abundance of eastern North American merlins Falco columbarius, a primary predator of adult plovers, as a covariate on adult survival via a parallel state-space model, accounting for the influence of an imperfectly observed process (i.e. predation pressure) on population viability. Mean plover abundance increased from 18 pairs in 1993 to 75 pairs in 2016, but annual population growth (λt) was projected to be 0.95 (95% CI 0.72–1.12), suggesting a potential decline to 67 pairs within 10 years. Without accounting for an expanding merlin population, we would have concluded that the plover population was projected to increase (λt = 1.02; 95% CI 0.94–1.09) to 91 pairs by 2026. We compared four conservation scenarios: (1) no proposed management; (2) increased control of chick predators (e.g. Corvidae, Laridae, mammals); (3) increased merlin control; and (4) simultaneous chick predator and merlin control. Compared to the null scenario, chick predator control reduced quasi-extinction probability from 11.9% to 8.7%, merlin control more than halved (3.5%) the probability and simultaneous control reduced quasi-extinction probability to 2.6%. Synthesis and applications. Piping plover recovery actions should consider systematic predator control, rather than current ad hoc protocols, especially given the predicted increase in regional merlin abundance. This approach of combining integrated population models with Bayesian population viability analysis to identify limiting components of the population cycle and evaluate alternative management strategies for conservation decision-making shows great utility for aiding recovery of threatened populations.
Bibliographical noteFunding Information:
U.S. Fish and Wildlife Service, Grant/ Award Number: F17AC00427; National Science Foundation, Grant/Award Number: EF-1702635; U.S. Fish and Wildlife Service and the Michigan Department of Natural Resources ; USDA National Institute of Food and Agriculture
We are grateful to all who have been involved in annual plover banding and monitoring efforts for nearly 25 years. We thank the University of Michigan Biological Station for continued support of piping plover research efforts and G. DiRenzo for statistical insight. We greatly appreciate the IPM-BPVA example and template code provided by M. Schuab and M. Kéry at their integrated population modelling workshop held at Patuxent Wildlife Research Center. We also appreciate the insightful written comments provided by the Associate Editor J. Rhodes, D. Gibson and an anonymous reviewer. We thank the Great Lakes Restoration Initiative for support of S.P.S. for fieldwork and the USDA National Institute of Food and Agriculture (Hatch project 1007020) for support of F.J.C. S.P.S. was also supported by U.S. Fish and Wildlife Service (Cooperative Agreement Award F17AC00427) and the National Science Foundation (Award EF-1702635). Funding for data collection was provided by the U.S. Fish and Wildlife Service and the Michigan Department of Natural Resources. All capture, handling and observation of piping plovers were approved by the University of Minnesota Institutional Animal Care and Use Committee and federal endangered and threatened species and banding permits.
- Charadrius melodus
- conservation scenarios
- integrated population model
- management strategies
- piping plover
- population viability analysis
- predator control