3 Dec 2020

Golden White-eye dodges danger of invasive snake

For years, conservationists feared that this tiny songbird would fall prey to invasive tree snakes that had decimated bird populations on nearby islands. Thankfully, biosecurity measures seem to be holding back the invasion, bringing hope for this Critically Endangered species.

The Golden White-eye pollinates many of the islands' plants © Peter / Flickr
The Golden White-eye pollinates many of the islands' plants © Peter / Flickr
By Jessica Law

In the middle of the Pacific Ocean, you will find buried treasure – not in the ground, but flitting through the forests of Saipan and Aguijan in the Northern Mariana Islands. The Golden White-eye Cleptornis marchei may weigh only 20 grams, but it is worth more than its weight in gold as part of the ecosystem. Feeding on insects, fruits and nectar, it pollinates many of the islands’ plants. It also helps another small bird species, the Rufous Fantail Rhipidura rufifrons, to find food by flushing out insects when foraging. The two species can often be spotted in an unlikely procession, with the fantail following along in the Golden White-eye’s wake.

Unfortunately, for many years this species has been living in the shadow of extinction, as the threat of the invasive Brown Tree Snake Boiga irregularis slithered closer and closer to its shores. The carnivorous, nocturnal snake was accidentally introduced to the island of Guam by a US military cargo ship at the end of World War II. With no natural predators, the devastation was rapid. Surveys reported a 90% decline in most bird species within nine years of the snake’s invasion, and three bird species went extinct completely.

Worryingly, all goods imported to the Northern Mariana Islands are shipped through Guam, since both are overseas territories of the USA. When the snake established itself on islands near Saipan – the Golden White-eye’s biggest stronghold – conservationists feared that it would become another on the long list of avian casualties. Sightings of the dreaded snake around Sapian’s port seemed to confirm these fears. This looming threat led to the species being classed as Critically Endangered in 2004.

However, recent reports show that there have been no confirmed records of Brown Tree Snake on Saipan for 20 years. It seems that biosecurity measures put in place to prevent the snake’s spread are working, and the predicted disaster has not come to pass. This, combined with the successful translocation of an “insurance population” of Golden White-eyes to the nearby island of Sarigan, means the bird’s future may not be as bleak as previously thought. It isn’t completely in the clear – it still has a very small range, and habitat degradation is a growing concern. But it is nonetheless a shining beacon of hope, showing us that no extinction is a foregone conclusion.