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Adult female Mascarene petrel, (Pseudobulweria aterrima), with large egg bump. This species is critically endangered.
Adult female Mascarene petrel, Pseudobulweria aterrima, with large egg bump (arrow), photographed south of Réunion Island in the southern Indian Ocean. This species is critically endangered with a small and steadily-declining population. Photograph: Hadoram Shirihai/BirdLife International.
Adult female Mascarene petrel, Pseudobulweria aterrima, with large egg bump (arrow), photographed south of Réunion Island in the southern Indian Ocean. This species is critically endangered with a small and steadily-declining population. Photograph: Hadoram Shirihai/BirdLife International.

Pregnant Mascarene petrel shows off ginormous egg bump as she soars over open seas: picture

This article is more than 9 years old

Ornithological paparazzi snapped photos of the critically endangered seabird south of Réunion Island in the southern Indian Ocean.

A critically endangered Mascarene petrel, Pseudobulweria aterrima, with a very pregnant egg bump is taking centre stage by storm in the ornithological world on Thursday. This mysterious seabird was expected to lay her egg – and she lays only one egg per season – within hours after being photographed on 22 December 2012 by ornithological paparazzi.

Adult Mascarene petrel, Pseudobulweria aterrima. This individual lacks an egg bump. Photograph: Hadoram Shirihai/BirdLife International.

The bird, who looked fit and healthy, was photographed as she glided languidly over open seas about 25 miles south of the island of Réunion in the southern Indian Ocean. She appeared calm as she geared up for her upcoming sweat-breaking egg-laying ordeal deep within her nesting burrow on the cliffs of Réunion. (Petrels produce exceptionally large eggs compared to other similarly-sized bird species.)

Geographic position of Réunion, Indian Ocean. Photograph: Hadoram Shirihai/British Ornithologists' Club

The reclusive female Mascarene petrel and 17 of her friends, along with the usual rabble of look-alikes and pretenders, were lured into camera range (“position 2”, on map below) by the scent produced by a trail of “chum” – a smelly mixture of fish oil, entrails and bait (chum sometimes also includes floating chunks of beef fat, or suet). This concoction is dripped over the side of a boat when it is dozens of miles or more offshore.

Study area: at-sea GPS positions where Mascarene Petrels, Pseudobulweria aterrima, were recorded (red). Most were heading towards land as dusk approached. Position 1: two on 17 December 2012. Position 2: 14 birds on 18 December 2012 and 17 on 22 December 2012. Approximate locations of calling birds marked purple. Photograph: Google/DigitalGlobe

The mother-to-be was clad in a chic ensemble of fresh all-dark plumage. A pop of colour was provided by unique and delicate straw-yellow markings on her neck, accentuating her lovely features; her square-shaped head and powerful hooked bill that was adorned on its top base with a perky tubed nose. Her athletic look was emphasized by her long wings, fairly uniform in width, that featured rounded tips. When sitting on the surface of the sea, the tips of her wings projected distinctly beyond the length of her tail.

She was first spotted whilst approaching the boat.

Initial sighting of the egg-carrying female Mascarene petrel.
Initial sighting of the egg-carrying female Mascarene petrel. Photograph: Hadoram Shirihai/Tubenoses project.

“Against the background of a pinkish-orange sunset, with Réunion Island in the distance, I spotted a petrel through my camera’s viewfinder”, said Hadoram Shirihai in a press release. Mr Shirihai was the ornithological paparazzo and first author on the article published today in the Bulletin of the British Ornithologists’ Club.

“Almost immediately I saw the outline of an egg, a huge bump at its belly. I called out to the other expedition members -- ‘she has an egg, she has an egg...’. She flew close to the boat which gave me the unique chance to photograph her just before the sun set. It was a magical moment, and to think that in less than an hour she would probably lay her egg and contribute to the future survival of this threatened species.”

The swollen area is just above the cloaca, indicating that it is indeed an egg and not an abnormality or growth.

Adult Mascarene petrel, Pseudobulweria aterrima, off Réunion, December 2012; note unique jizz of heavy bill, well-projecting neck and head, long posterior body, graduated tail, and long slender almost even-width wings with rounded tips. Photograph: Hadoram Shirihai/BirdLife International.

The expectant mother looked relaxed during her pre-holiday outing, and seemed to be enjoying the unexpected free meal in the company of her companions.

“These are first photos of Mascarene petrel taken at sea. Up until now the only shots are of grounded birds, brought down due to artificial lighting on Réunion, the breeding island”, said fellow ornithological paparazzo and expedition member, Tony Pym, a co-author of the paper. (Note: more than 70% of grounded birds were found in the yellow area on study area map, above.)

Rare and elusive, the Mascarene petrel is one of the world’s least-known seabirds.

“With some estimates of only a few dozen breeding pairs of Mascarene Petrel our at-sea records suggest there are more individuals than thought, and that unknown colonies somewhere on the island have ensured the future of this species, at least for now”, added Vincent Bretagnolle, another co-author.

“This exciting discovery provides important information on a very poorly known and globally threatened seabird”, said Roger Safford, BirdLife International’s Preventing Extinctions Programme Manager, who was not part of the expedition.

“The finders are to be congratulated on their dedication. Their discovery was no accident, combining meticulous planning and research.”

The ornithologists chartered a privately-owned 10-metre sports fishing boat in Grand Bois, close to St. Pierre in southern Réunion. The boat usually drifted near the chum trail, which allowed the birds to move freely along the slick and to feed undisturbed, whilst providing excellent angles for observing and photographing seabirds that had already been attracted as well as late arrivals to the feast.

In total during the expedition, 33 Mascarene petrels were observed, and 12 were photographed. In the newly published paper, the species’ flight and behaviour are described, and a detailed comparison is made to other very similar “confusion species”, all for the first time.

The Mascarene petrel is classified as Critically Endangered on BirdLife International’s IUCN Red List because it is estimated to have an extremely small breeding population. This nocturnal species is assumed to be undergoing a continuing decline due to predation by human-introduced pests, particularly cats and rats, and mortality caused by light pollution.

“For most Critically Endangered species like Mascarene petrel there is still hope for their survival,” noted Dr Safford in a press release.

“BirdLife and its partners are working to save the world’s most threatened species from extinction. With the right conservation action, often underpinned by sound science, we have improved the populations and fortunes of many species. “

“Mascarene petrel is set to benefit from direct conservation action on Réunion. The Parc national de La Réunion authorities have been awarded funds from EU LIFE+ this year to reduce threats and undertake conservation actions for the petrel. This will involve working on the ground with local conservation organisations such as SEOR (Société d’Etudes Ornithologiques de La Réunion).”

Adult Mascarene petrel, Pseudobulweria aterrima, south of Réunion Island in the Indian Ocean. This species is critically endangered. Photograph: Hadoram Shirihai/Tubenoses project.

Sources:

Shirihai H., Pym T., San Román M. & Bretagnolle V. (2014). The Critically Endangered Mascarene Petrel, Pseudobulweria aterrima: identification and behaviour at sea, historical discovery of breeding sites, and breeding ecology on Réunion, Indian Ocean, Bulletin of the British Ornithologists’ Club, 134 (3) 194-223. [open access]

Press release.

Many thanks to Adrian Long, Head of Communications at BirdLife International, for assisting me with this piece and the tweeters on the British Ornithologists’ Union twitter feed for freely hosting the PDF.

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When she’s not out birding, GrrlScientist can also be found here: Maniraptora. She’s very active on twitter @GrrlScientist and sometimes lurks on social media: facebook, G+, LinkedIn, and Pinterest.

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