Cat and Mouse vs. Bird on a Tropical Island

The island of Fernando de Noronha has always had a small number of bird species, which makes the few that survive here all the more unique, and all the more important to protect.

I’ve been here for the past few weeks, getting to know the island, its birds, and the invasive species I came here to study.

As a small oceanic island nestled just south of the equator in the Atlantic Ocean, its always been hard for species to find their way to Fernando de Noronha. In fact only four species of land birds ever made it: a fly catcher, a vireo, a dove, and a rail. Even more bizarrely, at some point in the past a rat species (Vespucci’s rat) managed to combination raft and swim what is today some 220 miles to colonize the island.

This means that unlike on most remote islands, the land birds here evolved alongside a rat species, conferring some resistance to subsequent rat invasion. It wasn’t enough though for the rail, which is now extinct.

The flycatcher (Elaenia ridleyana) and vireo (Vireo gracilirostris) have been here so long they have evolved into new species distinct from those on the mainland. Although common across the island, they are by virtue of their isolation classified as endangered on the Brazilian threatened species list due to their small area of distribution.

New species are arriving with humans; sparrows (Passer domesticus) only arrived in 1989 and are now abundant.

An endemic flycatcher (Elaenia ridleyana) calls from a tree on Fernando de Noronha
An endemic flycatcher (Elaenia ridleyana) calls from a tree on Fernando de Noronha. (Photo by James Russell)

Seabirds have also found the island, using it as a valuable breeding site. Twelve species of seabird breed at Fernando de Noronha, representing all major tropical seabird groups. Historical records on first arrival describe “innumerable trees full of so many sea- and land-birds that they were beyond count.”

Today habitat loss, human disturbance, and—most importantly—introduced predators such as cats, rats, and the tegu (a large Brazilian lizard), mean seabirds on Fernando de Noronha are largely restricted to the smaller secondary islands around the coast.

A small colony of masked boobies (Sula dactylatra) hold on to one point on the main island, but signs of cats are present all around. The red-billed tropicbird (Phaethon aethereus) is perilously in decline, with fewer than 10 now seen around the island. Fifteen Audubon’s shearwaters (Puffinus lherminieri) are banished to rocky cliffs on a tiny offshore island, within the swimming range of rats.

A masked booby (Sula dactylatra) breeds on the edge of a cliff, their last stronhold on the main island of Fernando de Noronha. (Photo by James Russell)

There is hope for the protection of all these species on this isolated Brazilian island if the introduced predators can be managed. On other islands around the world, much bigger than Fernando de Noronha, eradication of cats and rats has led to rapid re-colonization of new habitat by seabirds.

Imagine once again visiting an island where you could not even count the number of birds you see. I am excited by the potential for successful conservation on the island, the motivation of the local people, and the continuation of our work when I next return to Fernando de Noronha in 2016.

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Meet the Author
Conservation biologist Dr. James Russell works throughout the world on remote islands and other sites to provide conservation solutions by applying a combination of scientific methods. Follow James on National Geographic voices for regular updates on his own work or other exciting developments in island conservation.