Replacing Sources with Sinks: When Do Populations Go Down the Drain?

Authors

  • Jason C. Keagy,

    Search for more papers by this author
    • 1

      Institute for Integrative Bird Behavior Studies, The College of William and Mary, Williamsburg, VA 23187, U.S.A.

    • 2

      Department of Biology, The College of William and Mary, Williamsburg, VA 23187, U.S.A.

  • Sebastian J. Schreiber,

    Corresponding authorSearch for more papers by this author
    • 1

      Institute for Integrative Bird Behavior Studies, The College of William and Mary, Williamsburg, VA 23187, U.S.A.

    • 3

      Department of Mathematics, The College of William and Mary, Williamsburg, VA 23187, U.S.A.

  • Daniel A. Cristol

    Search for more papers by this author
    • 1

      Institute for Integrative Bird Behavior Studies, The College of William and Mary, Williamsburg, VA 23187, U.S.A.

    • 2

      Department of Biology, The College of William and Mary, Williamsburg, VA 23187, U.S.A.


Address correspondence to S. Schreiber, email sjs@math.wm.edu

Abstract

We investigate the scenario in which some amount of higher quality habitat is destroyed and is then replaced by some undetermined amount of lower quality habitat. We examined how much low-quality habitat would need to be created to maintain the equilibrium population abundance in the entire geographic area. Using a source–sink model, we find that (1) the number of hectares of created habitat per hectare of destroyed habitat must equal the ratio of the high-quality habitat's productivity to the low-quality habitat's productivity, however, (2) if the created habitat is a sink, then there is a threshold fraction of destroyed high-quality habitat below which the initial population abundance cannot be maintained through the creation of habitat. We illustrate these results using data on Red-winged Blackbirds (Agelaius phoeniceus) in two different regions where high-quality habitat is being replaced by or converted into lower quality habitat.

Ancillary