Good news: The frigatebird, one of the world’ rarest seabirds, has returned to remote Ascension Island in the south Atlantic Ocean after 150 years. At the start of December, ornithologists sighted frigatebirds guarding two nests with eggs, the first signs that the species has bred on the island since Charles Darwin visited in 1836. Since then, a small colony of about 10,000 birds has survived on Boatswain Bird Island, a rocky outcrop that has left them easily exposed to disease and oil spills.
But here’s the bad news. The island’s entire population of feral cats has been killed, in a program costing more than more than £500,000 under the auspices of the Royal Society for the Preservation of Birds (RSPB) and the British Foreign Office.
The cats were only there because of humans. In the 19th century, Ascension Island had a population of more than 20 million seabirds. The frigatebird was thought particularly important as it was only found on the island; the males of the species have a distinctive red sac on their chests that is inflated during courtship. With humans came other unintentional settlers — rats — who began to kill off the birds’ chicks. Cats were accordingly imported but they too started to kill the chicks so that, when Darwin arrived on the island, only a few frigatebirds remained and these were also soon killed after he left. Boatswain Bird Island where the last colony of birds lived was inaccessible to cats.
Starting in December of 2006, the RSPB started its program to kill the wild cats. Islanders who had pet cats were instructed to collar and microchip them. Traps were set for the feral cats who were put down after being caught.
It’s thrilling to learn that a species has been brought back from the very edge of extinction. But the fate of the cats, who were of course not on Ascension Island by any of their own doing, is at least questionable. Could not the cats, once trapped, have been transported to an off-island shelter and put up for adoption?
On another island in the south Atlantic, South Georgia (2000 miles off the southern tip of Argentina), scientists are hoping to eradicate the population of rats. Their plan, part of the Habitat Restoration Project, involves not bringing in cats but scattering rat poison (dropped from three helicopters) over the island. Species endemic to South Georgia, such as the South Georgia Pipit, have retreated to offshore inlets and island that are rodent-free, but this is likely to change. Due to global warming, two glacial barriers are disappearing and the fear is that additional species of ground-nesting birds — including storm petrels, prions, diving petrels and blue petrels, who have all but abandoned the main island — will be threatened by the rats.
Conservationists acknowledge that at least some birds are likely to perish by consuming the rat poison. But such “collateral damage” is inevitable, the German news magazine, Der Spiegel notes.
In other words, as in the case of the killing of feral cats to bring back the frigatebird population, innocent animals are perishing as humans seek to undo the damage they caused. If anyone needs a lesson in how humans wreak havoc on wildlife and then create more in attempting to undo the damage, the cases of Ascension Island’s frigatebirds and the feral cats, and of the animal life on South Georgia, provide plenty to learn from.
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