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Island Eagles Relocation Project

Island FoxIn cooperation with a variety of agencies and organizations, we have been attempting to develop non-lethal means of removing predatory birds having an impact on threatened or endangered species. This situation usually arises when the imperiled species tends to nest or exist in small, relatively localized areas. Although predation is of course a normal occurrence in the wild, in these cases, individual predators can have a severe impact on the already depleted population of prey, or their reproductive attempts in a given breeding season.    Our method is to capture and move the individual of concern to a remote location in suitable habitat. In most cases, these are non-breeding individuals that would not be expected to be as highly motivated to return to the capture site as a breeding adult might. However, we have so far found that in a few cases where we have moved breeders outside the breeding season, they have shown no inclination to return during the life of the transmitters we apply, and survivorship of the birds we have followed has been excellent.

Currently, we are working to remove golden eagles from the northern Channel Islands in California in cooperation with the US Fish and Wildlife Service, National Park Service and the Nature Conservancy. Golden eagles have only recently colonized the islands, likely owing to an abundance of feral animals such as pigs (no large mammals are native to the islands). Unfortunately, UCLA researcher Gary Roemer has discovered that the eagles are having a severe impact on the island fox, a small endemic species of fox roughly the size of a house cat, with a separate subspecies on each island.  These foxes have no native predators, and they are disappearing precipitously from the islands.

To date, we have released thirty-one eagles. Because of the size of the eagles, we are able to outfit them with long-lived satellite transmitters, which allow us to remotely determine the location of each eagle, and give us a long-term look into their movements and survival. This is vastly more efficient than trying to track their movements using ground-based telemetry, as the latter’s signal can easily be lost if they move out of the immediate release area, sometimes requiring airplane flights to find them. The transmitters will fall off the eagles at roughly the end of the transmitter battery life.

Satellite telemetry map for the island eaglesThis map shows the movements of those golden eagles affixed with satellite transmitters while the transmitters lasted. None of the eagles appeared to attempt a return to the islands, including adults who previously bred there. Two adults did head southward during fall/winter, but returned to the north for the summer. No banded eagles have been recaptured or resighted on the Islands to date.

Select map to display enlarged view