The Birds at the End of the World

The Birds at the End of the World

Euan Furness talks to Dr Michael Brooke, Curator of Ornithology at the Cambridge University Museum of Zoology, about his work finding birds in remote places

Even today, hundreds of scientists around the world are discovering new and amazing things that have been hiding right under our noses. Some are also discovering things that were not really hiding at all but were just a very long way away from anyone interested in them. The ‘frontiers of science’ do not always have to be metaphorical.

Consider this: where would you look for a seabird colony that nobody else could find? The coast would seem like a good start but, at least in the case of Hornby’s storm petrel (a blackbird-sized seabird closely related, believe it or not, to albatrosses), you would be a long way off target. That is because this particular seagoing bird lives deep in the Atacama Desert, more than seventy kilometres inland in a more than 80,000 square kilometre chunk of Pacific South America which, with the exception of the poles, is generally considered to be the driest place on earth.

The extreme aridity of the Atacama stems from its position between the Andes to the east and the Chilean Coastal Range to the west. These mountain ranges block almost all moisture from reaching the desert. It is probably no surprise, then, that nobody was looking for storm petrels on these high peaks. There was a search at lower altitudes, but no higher than around fifteen-hundred meters above sea level (merely the height of Ben Nevis). Given that nobody had ever seen a Hornby’s storm petrel nest until April 2017, it is worth asking why the Atacama Desert was being looked at in the first place.

“Naturally mummified fledglings [young birds] would occasionally turn up in the desert, so we got the impression that they must be nesting there somewhere,” says Dr Michael Brooke. “There were also records of birds in the region from the early 1900s nitrate mining era.” Mike is the Cambridge University Museum of Zoology’s Curator of Ornithology and a long-time researcher of birds that live in the most remote parts of the world.

Mike searched the Atacama Desert for the elusive Hornby’s storm petrel twice: once in 1999 and once in 2000, each time spending (literally) forty days and forty nights in the wilderness, a task which sounds almost biblical. Although it would be another sixteen years before anybody found what Mike had been looking for, his work was not fruitless. When he explained to a passing truck driver that he was searching for “golondrina de mar” (literally, “sea swallow”) Mike was directed to a salt mine beside an ancient dried-up salt lake (called a salar). There, at the back of the repair garage, were half a dozen juvenile Markham’s storm petrels: another species, almost as elusive as Hornby’s.

Acting on Mike’s report, a group of scientists from South America led by Fabrice Schmitt returned to the mine several years later and found a breeding colony of Markham’s storm petrels nesting between the salty slabs of Salar Grande.

There aren’t many places in the world quite like the Atacama Desert, but there are plenty more remote. Most of these are islands and Mike has been to a lot of them too, always with birds on the brain.

Henderson Island is located about half way between Auckland and Ecuador: almost as far from any major landmass as it is possible to get. Probably partly because of this isolation, and definitely partly by good luck, Henderson has remained almost untouched by human influence with one notable exception: the Polynesian rat (Rattus exulans) which was introduced by human settlers expanding across Polynesia almost 1000 years ago. The island, one of the Pitcairn Islands, was claimed by the British in 1819 (by which time the Polynesians were long gone) and in the absence of any human occupants to object to imperial rule it has remained British ever since.

The Sir Peter Scott Commemorative Expedition to Henderson Island took place in 1991-92 and was composed of all manner of scientists including botanists, geologists, archaeologists and, of course, ornithologists (including Mike). Although much focus was on the investigations into Polynesian settlement, the expedition also surveyed the populations of two little-known seabirds: the Murphy’s petrel (Pterodroma ultima) and the Henderson petrel (Pterodroma atrata). Like many island animals, both turned out to be suffering from the impact of the rats.

“The parent petrels proved totally incompetent at chick protection,” Mike tells me, and they aren’t the only ones: island birds have a long history of not understanding what rodents are or how to avoid them. On Gough Island, a sub-Antarctic island in the Atlantic, even giant birds like albatrosses can be killed by swarms of invasive mice. The mice here have grown larger than anywhere else in the world, but they weren’t here at all before humans came. The birds simply never learned how to defend themselves.

Wondering whether the terrible breeding success of the petrels might have been a one-off, Mike returned to the island in 2003 to re-survey the population. The story was the same, but all hope was not lost.

“In the noughties, the idea of getting the rats off Henderson Island was beginning to look technically feasible,” Mike explains. However, that did not make it
a simple job: Henderson Island presented a couple of confounding factors which made dropping poisoned rat-bait more complicated.

The first problem was the land crabs. These were immune to the rat poison but would potentially eat so much of the bait that there wouldn’t be enough left to kill off all of the rats. The second problem was the rails (a group of water birds, like moorhens). Like many islands, Henderson was home to an endemic species of flightless water-bird (the Henderson crake) which, unlike the crabs, could quite easily be killed by the rat poison; a potential disaster.

Mike returned to Henderson Island in 2009 to see if these problems could be solved. Finally, it was decided that removing the rats should be possible.

In August 2011, seventy-five tonnes of poisoned rat bait were dropped onto the island at a cost of £1.5 million
while a batch of rails were held captive, protected from access to the bait. For seven months not a single rat was seen. However, this happy state did not last; a National Geographic crew visiting the island in March 2012 saw a rat, and by April the rat population was growing rapidly. Genetic sampling showed a bottleneck of eighty individuals, down from the eighty-thousand before the extermination attempt, but enough that the population could recover.

Since then, Mike has been trying to figure out what went wrong and how a second attempt might be made to remove the rats. “Just a very small percentage of rats, for whatever reason, prefer to eat natural food to the bait pellets,” he suggests. “Could you add some attractant, the equivalent of chocolate truffles, to the bait?”

This failure hasn’t stopped Mike from studying the Henderson Island birds; if anything it makes study more urgent. Thanks to RSPB (Royal Society for the Protection of Birds) staff, GPS trackers have been placed on Murphy’s petrels to find out where they’ve been feeding, and have revealed an extraordinary trip. The birds forage at sea for
as many as twenty days at a time, flying in loops as long as fifteen-thousand kilometres which take them more than four-thousand kilometres from their home while their mate protects a single egg back on Henderson Island. Mike explains this more thoroughly in “Far from Land”, his new book published in March 2018.

There has not yet been a second extermination attempt on Henderson Island; the first one was expensive enough, and in light of its failure a second one would have to be even more thorough. We can only hope that, when the rats are finally removed, some of these extraordinary birds are still around to be appreciated by generations to come. Whether it is in the Atacama Desert, the Pitcairn Islands or elsewhere, such rare creatures are worth remembering. As long as there are scientists who are willing to go to the ends of the earth (or as close to them as they can get) to find and protect them, there is hope that birds like these will flourish, safe from human impact.

Euan Furness is a 3rd year Zoologist at Clare College. Artwork by Sean O’Brien