Africa
13 Jun 2017

After 130 years, the Mascarene masquerade is over

With the help of infrared binoculars, GPS and a heck of a lot of rappel rope, we've managed for the first time to scale the sharp, inaccessible cliffs where the Mascarene Petrel nests, and see one of these Critically Endangered birds' nesting colonies for ourselves

Mascarene Petrels in their burrow © LIFE+Petrels
By Alex Dale

It's easy to appreciate how the Beck's Petrel's breeding grounds have managed to evade human eyes for so long, given that their potential range spans the length of a vast, little-explored archipelago.

But what if we were searching for the breeding grounds of a different petrel species - one whose range is confined to a single, remote island? That would be a piece of cake (or chum, if you prefer) in comparison, right?

Well, not necessarily. We're in Reunion, a small, French-owned volcanic island in the Indian Ocean, situated between Madagascar and Mauritius. It is here, and only here, that you'll find the Mascarene Petrel Pseudobulweria aterrima, another Critically Endangered seabird, and indeed one of the 15 rarest and most threatened bird species in the world, with an estimated global population of just 100-200.

A rare shot of a Mascarene Petrel, taken during a prospecting mission at sea. © LIFE+Petrels

Even so, with such a limited range, you wouldn't necessarily expect the Mascarene Petrel to pull a disappearing act. Yet, like the Beck's Petrel Pseudobulweria becki, this ocean-faring bird is so elusive that it once went unseen for many decades. The dramatic discovery of a grounded bird on the island in the 1970s was the first sighting for nearly a century, and it would be another 25 years before another specimen turned up. In between these long droughts, all we’ve had to go on is its haunting nocturnal calls, which have inspired many Creole tales and legends on the island.

Which is a problem, because if there's one thing we know for sure about one of the world's most poorly-understood birds, it's that the Mascarene Petrel is in trouble. The species' already slim numbers are suspected to be thinning further still as a result of two man-made factors. The first is light-induced mortality – a result of the birds getting disorientated and crashing as a result of urban lights. A public awareness campaign on the island organised by Reunion National Park - “Nights Without Lights” - has already done much to reduce the death toll.

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The other threat, however, will prove a lot harder to dim – namely, nest predation by introduced mammals such as cats and rats. Invasive species are a leading cause of island-endemic bird extinctions worldwide, but BirdLife's recent successes in French Polynesia, where we've managed to eradicate introduced mammals on five of six targetted islands, serves as inspiration that their spread can be halted.

However, the situation for every species is different, so before we can develop an effective conservation strategy for the Mascarene Petrel, we need to better understand its ecology and breeding habits. No mean feat, when you're talking about a rare, strictly nocturnal seabird suspected to nest in burrows high up on sharp, inaccessible cliff edges.

Here it is: the first Mascarene Petrel breeding burrow to be seen by human eyes.

However, this past November, following more than 15 years of research from an international team of ornithologists, an EU-funded LIFE+Petrels project team managed to successfully discover an active Mascarene Petrel breeding colony for the first time ever. It's a major breakthrough in our bid to better understand how to protect this species, and it was made possible thanks to a combination of old-school fieldwork and cutting-edge technology.

“The Mascarene Petrel is only active at night, so to track its movements we needed the help of a new technological device - military infra-red binoculars” says Patrick Pinet,  Scientific Manager of the LIFE+Petrels project. “As far we know it's the first time this tool was used for wildlife conservation”.

The tool was acquired by the LIFE+ Petrels team thanks to a partnership with Mercantour National Park, an alpine wildlife refuge on the French-Italian border. They were used, in conjunction with acoustic recordings and thousands of hours of observational fieldwork, to pinpoint cliff edges where the birds could frequently be seen landing – indicating a likely breeding colony.

Once one such spot was identified, in a remote area of the south of the island, the next step was for a human expedition team to brave the steep, treacherous terrain to verify the colony. “We spent five hours walking in vertically sheer cliff tropical woodland up to 700m, after that we made a rappelled down 50 feet to reach the place we identified with IR binoculars” recalls Pinet. “The breeding colony is located in a crumbling, infirm volcanic cliff where you wouldn't want to stay for long”.

An IR shot of the petrels inside their burrow. © LIFE+Petrels

Because of the steep cliffs, the explorers could not rely on GPS alone to locate the suspected colony, and so were forced to remain in contact with the rest of the team down below, who parlayed instructions to them via walkie-talkies. Fortunately, the team got lucky and found the colony at the first time of asking – perhaps guided by their nose, since the colony's strong fishy smell could be detected from a distance of around 30 meters. The discovery of these burrows means the team can now move onto brainstorming practical ways to secure the species' future.

“The first, and most urgent step, is to protect the breeding colony from invasive predators” says Pinet. “The second step is to take further measures to ensure the species' continued survival.

“We are currently considering two options: the first is to build a barrier around an established colony to keep predators out. The second is the construction of an artificial colony close to the sea, to avoid the issues created by urban light.”