Survivorship of the Galapagos Hawks after goat eradication

in Neotropical Program: Student Education and Research: Ecuador: Ecology and demography of the Galapagos Hawk:

Status: Active, started in 2008

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Goals:

Investigate survivorship of floater and territorial hawks after goat eradication, and understand the consequences of an ungulate eradication program on the Galapagos Hawk population from Santiago Island.

Background:

The study analyzed changes in hawk survivorship and population size attributable to the goat eradication on Santiago Island. We evaluated the impact of intrinsic and ecological factors interacting with the polyandrous breeding system on the survivorship of the Galapagos hawk. The contribution of sex, territorial group size and body size (factors directly related to the breeding system) and their relationship to survivorship over the years before, during, and after eradication was evaluated. To gain insights into the underlying mechanism by which goat eradication may have affected hawk survivorship, we tested the importance of the vegetation structure of the territory. We also analyzed population sizes of the floater fraction of the population (mostly consisting of juveniles), asking whether patterns of changing abundance were related to the goat eradication.

Recent Results:

This project was completed in 2010. Jose Luis Rivera completed his MSc in Biology at the University of Missouri Saint Louis. Main findings were:

  • Juvenile floaters showed a drastic decline in 2007, 2008 and 2010. This decline was attributed to the completion of goat eradication in 2006, and subsequent habitat changes.
  • Adult survivorship declined after the goat eradication. Additionally, group size positively affected adult survivorship in this cooperative polyandric raptor, presumably reflecting the benefit of shared defense and offspring provisioning during harsher conditions.
  • Changes in hawk survivorship after goat eradication are an example of unforeseen consequences of an eradication program aimed at ecosystem restoration

Project Links:

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Location Note:

Santiago Island, Galapagos Islands, Ecuador

Species involved

People involved in this project:

Rick Watson Ph.D. Vice President and Director of International Programs
Hernan Vargas Ph.D. Program director – Neotropical Science and Student Education
Patricia Parker UMSL, University advisor
Jose Rivera MSc student

Cooperating Partners:

  • Arkansas State University
  • Charles Darwin Foundation
  • Galapagos National Park Service
  • Offield Family Foundation
  • Swiss Friends of the Galapagos
  • The Galapagos Conservancy
  • University of Missouri Saint Louis
  • Whitney R. Harris World Ecology Center