A Second Home May Shore up Island Scrub Jay's Future

January 1, 2011 by Meghan Bartels

Conservationists often worry about species that have very small home ranges, like an island, because one event can easily affect the entire area. The island scrub-jay is a perfect example of this type of species—in fact, it's the only bird in the continental U.S. whose habitat is limited to a single island—and scientists want to make sure the bird has a long and healthy future.

blue bird holding acorn Island Scrub-Jay © Colin Woolley

That might be tough to come by. The island scrub-jay lives on Santa Cruz Island, which is one of Southern California's Channel Islands and about 100 square miles large. Although it is not considered threatened, a recent island-wide survey indicated a total population size of fewer than 2,500 island scrub-jays, and scientists don't know if that number has been holding steady or slipping in recent years.

At the moment, Santa Cruz Island is a welcoming home for scrub-jays. In the past twenty years, after sheep and other grazers were removed, the island's vegetation has bounced back to offer the birds healthy habitat. West Nile virus, which has affected bird populations throughout California, has not yet been reported on the island, nor have rats, which also hurt bird populations.

But this could change with very little notice. Climate change will make the island warmer and drier, which could increase risk of wildfires. The island also does not have any formal protection measures to keep West Nile, rats, and other threats away. So scientists working on Santa Cruz Island, including members of the Smithsonian Migratory Bird Center, have come up with a plan to protect the island scrub-jay.

On Santa Cruz, the plan has four parts. The first is to establish a protected captive breeding population. This program will allow scientists to learn the tricks of successful scrub-jay reproduction and release without imminent risk of extinction and will serve as an emergency reserve if some danger does strike Santa Cruz's birds.

Second, the scientists have been vaccinating some of the island's scrub-jay population against West Nile virus. A similar initiative is already protecting wild California condors, a species that experienced a serious population decline in the middle of the 20th century. Not every bird has to be vaccinated to provide protection for the species. But, vaccination is a short-term strategy.

The third recommendation is to establish formal biosecurity protocols for Santa Cruz Island to target risks like wildfires and invasive species. In ecosystems as in so many other situations, preventing a disaster is usually much cheaper than cleaning up the mess after that disaster.

The scientists' final recommendation is to investigate the option of establishing a second island scrub-jay population on Santa Rosa Island, next door to Santa Cruz. Millennia ago, these two islands were part of one larger island, Santarosae, and scientists have some evidence suggesting that scrub-jays may have lived on Santa Rosa as recently as the late 1800s. Wildlife translocations, as such a measure is called, are undertaken with caution, but there is precedent for this type of response, particularly on Pacific islands. The scrub-jay situation would need extensive further study before a translocation, which could have profound effects on Santa Rosa Island's ecosystem.

That wouldn't necessarily be a bad thing. Sheep and cows are long-gone from Santa Rosa, and non-native deer and elk have recently been removed. These animals have decimated vegetation coverage on the island, especially oak chaparral habitat used by jays. Because island scrub-jays disperse seeds, particularly acorns, they could help speed up the recovery of the island's vegetation. And if the program were a success, scrub-jays would have a second population to serve as insurance for the Santa Cruz Island population, increasing the species' chances of survival if something were to happen on their current home island.

Island scrub-jays won't be moved to Santa Rosa Island tomorrow, and such a step may never be deemed the right solution. But scientists hope that by taking this island bird under their wings, they can ensure the survival of this rare species for years to come.

This article summarizes the information in this scientific paper:

Scott A. Morrison, T. Scott Sillett, Cameron K. Ghalambor, John W. Fitzpatrick, David M. Graber, Victoria J. Bakker, Reed Bowman, Charles T. Collins, Paul W. Collins, Kathleen Semple Delaney, Daniel F. Doak, Walter D. Koenig, Lynda l Laughrin, Alan A. Lieberman, John M. Marzluff, Mark D. Reynolds, J. Michael Scott, Jerre Ann Stallcup, Winston Vickers, and Walter M. Boyce. 2011. Proactive Conservation Management of an Island-endemic Bird Species in the Face of Global Change. BioScience 61(12).

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