Shifting threats faced by the San Clemente sage sparrow

Authors

  • Brian Hudgens,

    Corresponding author
    1. Institute for Wildlife Studies, 55 Ericson Court Suite #1, Arcata, CA 95521-8912, USA
    • Institute for Wildlife Studies, 55 Ericson Court Suite #1, Arcata, CA 95521-8912, USA.
    Search for more papers by this author
  • Frederic Beaudry,

    1. Department of Wildlife, Humboldt State University, 1 Harpst Street, Arcata, CA 95521-8222, USA
    2. Institute for Wildlife Studies, 2515 Camino Del Rio South Suite #334, San Diego, CA 92108-3716, USA
    Current affiliation:
    1. Environmental Studies Division, Alfred University, 1 Saxon Drive, Alfred, NY 14802, USA.
    Search for more papers by this author
  • T. Luke George,

    1. Department of Wildlife, Humboldt State University, 1 Harpst Street, Arcata, CA 95521-8222, USA
    Search for more papers by this author
  • Sara Kaiser,

    1. Institute for Wildlife Studies, 2515 Camino Del Rio South Suite #334, San Diego, CA 92108-3716, USA
    Current affiliation:
    1. Department of Neurobiology and Behavior, Cornell University, W345 Seeley G. Mudd Hall, Ithaca, NY 14853-2702, USA.
    Search for more papers by this author
  • Nicole M. Munkwitz

    1. Department of Wildlife, Humboldt State University, 1 Harpst Street, Arcata, CA 95521-8222, USA
    2. Institute for Wildlife Studies, 2515 Camino Del Rio South Suite #334, San Diego, CA 92108-3716, USA
    Current affiliation:
    1. 347 Satley Hill Rd, Alfred Station, NY 14803, USA.
    Search for more papers by this author

  • Associate Editor: David King

Abstract

Threats to a species' persistence are likely to change as conservation measures reduce some threats, while natural and anthropogenic changes increase others. Despite a variety of potential underlying mechanisms, extinction threats will be manifested through one of the 3 components of population dynamics: reducing population growth potential, increasing population variability, or lowering the population ceiling. Consequently, effective management can be guided by monitoring programs and population models that examine each of these components. We examined the potential for a coupled monitoring and modeling effort to guide management of species-at-risk while accounting for evolving risks using the case study of the threatened San Clemente sage sparrow (Amphispiza belli clementeae). Originally listed due to a low population ceiling imposed by severe habitat loss, we found that the major threat to San Clemente sage sparrow persistence has shifted to low population growth potential driven by high juvenile mortality. We further found that successful mitigation of high juvenile mortality will shift the primary threat to drought frequency, which is predicted to increase on San Clemente Island as a consequence of global climate change. The latter shift is a consequence of the boom-bust ecology exhibited by San Clemente sage sparrows in response to rainfall—likely a common characteristic of short-lived terrestrial vertebrates in arid environments. Our ability to successfully recover this species hinges on a comprehensive monitoring and modeling program incorporating all 3 components of population dynamics informing changes in management priorities to reflect shifting threats. Our study indicates that the next critical step to recovering sage sparrows is to understand and mitigate the causes of high juvenile mortality. In response to these predictions, the United States Navy has funded a radio-telemetry study to determine the cause(s) of juvenile mortalities. © 2011 The Wildlife Society.

Ancillary