Postcatastrophe Population Dynamics and Density Dependence of an Endemic Island Duck

Authors

  • NATHANIEL E. SEAVY,

    1. Hawaii Cooperative Studies Unit (Pacific Aquaculture and Coastal Resources Center, University of Hawaii at Hilo), United States Geological Survey, Pacific Island Ecosystems Research Center, Kilauea Field Station, Hawaii National Park, HI 96718, USA
    Search for more papers by this author
    • Point Reyes Bird Observatory Conservation Science, 3820 Cypress Drive 11, Petaluma, CA 94954, USA

    • E-mail: nseavy@prbo.org

  • MICHELLE H. REYNOLDS,

    1. United States Geological Survey, Pacific Island Ecosystems Research Center, Kilauea Field Station, Hawaii National Park, HI 96718, USA
    Search for more papers by this author
  • WILLIAM A. LINK,

    1. United States Geological Survey, Patuxent Wildlife Research Center, Laurel, MD 20708, USA
    Search for more papers by this author
  • JEFF S. HATFIELD

    1. United States Geological Survey, Patuxent Wildlife Research Center, Laurel, MD 20708, USA
    Search for more papers by this author

Abstract

ABSTRACT  Laysan ducks (Anas laysanensis) are restricted to approximately 9 km2 in the Northwestern Hawaiian Islands, USA. To evaluate the importance of density dependence for Laysan ducks, we conducted a Bayesian analysis to estimate the parameters of a Gompertz model and the magnitude of process variation and observation error based on the fluctuations in Laysan duck abundance on Laysan Island from 1994 to 2007. This model described a stationary distribution for the population at carrying capacity that fluctuates around a long-term mean of 456 ducks and is between 316 to 636 ducks 95% of the time. This range of expected variability can be used to identify changes in population size that warn of catastrophic events. Density-dependent population dynamics may explain the recovery of Laysan duck from catastrophic declines and allow managers to identify population monitoring thresholds.

Ancillary