Ecology and demography of the Galapagos Hawk
in Neotropical Program: Student Education and Research: Ecuador:Status: Active, started in 2008
All projects within this project:- Feeding ecology of the Galapagos Hawk after goat eradication (2009 – )
- Survivorship of the Galapagos Hawks after goat eradication (2008 – )
Goals:
Long-term monitoring of the Galapagos Hawk and its prey populations to document and understand the consequences of eradicating invasive mammals, like goats and rats, introduced to the Galapagos islands and the subsequent recovery of the biological community. Potential consequences include a shift in prey availability for the hawk as the biological community changes, and changes in the dispersal, demography and unusual social system of the hawks themselves.
Background:
The Galapagos Hawk is found only on the Galapagos Islands, and nowhere else on earth. It is the only diurnal raptor found on in the islands, which are located 600 miles off the Pacific coast of Ecuador. Studies of the species started in the early 1970’s. Since 1998 the hawks have been studied extensively and continually by a team led by Prof. Patricia Parker from the University of Missouri Saint Louis (UMSL) and collaborators in Ecuador. Since 2008, The Peregrine Fund has collaborated with UMSL, Galapagos National Park Service (GNPS), and the Charles Darwin Foundation (CDF) to study the endangered Galapagos Hawk and build local capacity for research and conservation by supporting and training Ecuadorian students in raptor research and ecological methods.
Three goats were introduced to Santiago Island in 1813 and by the early 1970s the population of this exotic herbivore had reached an estimated 100,000 individuals. Overgrazing resulted in ecosystem degradation and loss of endemic biodiversity (plants and animals found only there). Land iguanas had became extinct and giant tortoises were severely decimated by a combination of human persecution, food competition with goats and predation by wild pigs (Sus scrofa) and black rats (Rattus rattus).
The removal of invasive species is expected to have a positive impact by allowing endemic biological communities to recover. However, there may be unforeseen negative consequences, particularly when the eradicated species had replaced the function of an extinct component of the original ecosystem. This situation exists on Santiago Island, which is now largely without vertebrate herbivores after the successful eradication of goats in 2006. Santiago is believed to be the largest island in the world ever purged of exotic ungulates, where native herbivores had been driven extinct (Land iguanas) or nearly so (Giant tortoises) leaving the island largely without vertebrate herbivory.
Our study is part of a long-term research program of this unique island raptor and its prey populations to test several possible consequences of the eradication of ungulates and the subsequent recovery of the biological community.
On most island, the hawk exhibits a unusual “cooperative polyandrous mating system” in which each breeding territory includes one female who typically mates with two or more males, with all males helping to raise the chicks. The membership of these territorial groups on Santiago can vary greatly from just pairs to groups of up to eight males. The hawk also breeds on eight of the human-uninhabited islands, and breeding populations have been lost from three of the now human-inhabited islands.
Santiago Island is an un-inhabited island located in the center of the Galapagos archipelago with a peak elevation of 907 m (about 3000 feet). The study is conducted at two study sites on Santiago: James Bay (Western Santiago) encompassing 25-28 breeding territories and Sullivan (Eastern Santiago) with 6-8 territories. Between 1998 and 2010, 198 territorial adults and 390 juveniles were banded. Efforts are made every year to band all adults and young hawks at both study sites.
This project has two primary components, each led by an Ecuadorian graduate student. The survivorship component initiated in 2008 and the feeding ecology component initiated in 2009. The Peregrine Fund and UMSL also collaborate with The Galapagos National Park Service and the Charles Darwin Foundation in conducting hawk population surveys across the whole archipelago. We also provide scientific advice to the Galapagos National Park Service on how to mitigate the effects of eradication of invasive mammal species (particularly rats) on the hawk populations from various islands where ecological restoration efforts are underway.
Recent Results:
2010- Survivorship study completed and Ecuadorian MSc student graduated
- Surveys for un-paired adults (“floaters”)were conducted for 8 days for a total of 128 surveys
- Census, assessments of reproductive activity and evaluation of group membership of territorial hawks were completed on James Bay and Sullivan Bay
- Nine hawks were banded and blood samples collected for genetic and health evaluation
- Assisted CDF and GNPS in hawk surveys on Rabida, Pinzon, Bainbridge, and Bartolome islands prior initiation of rat eradication.
2009
- Feeding ecology study initiated with involvement of one Ecuadorian MSc student.
- Surveys for floaters were conducted for 14 days for a total of 224 surveys
- Census, assessments of reproductive activity and evaluation of group membership of territorial hawks were completed on James Bay and Sullivan Bay
- 107 hawks were banded and blood samples collected for genetic and health evaluation
2008
- Survivorship study initiated with involvement of one Ecuadorian MSc student
- Surveys for floaters were conducted for 6 days for a total of 70 surveys
- Census, assessments of reproductive activity and evaluation of group membership of territorial hawks were completed on James Bay and Sullivan Bay
- 53 hawks were banded and blood samples collected for genetic and health evaluation
Project Links:
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Location Note:
Santiago Island, Galapagos Islands, Ecuador
Species involved
- Galapagos Hawk — Buteo galapagoensis
People involved in this project:
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
Combined Federal Campaign # 10639
