Mascarene Petrel Pseudobulweria aterrima Scientific name definitions

The Mascarene Petrel is just one of a suite of exceptionally rare petrels in the genus Pseudobulweria. Like its congener, the Fiji Petrel (P. macgillivrayi), this species is regarded as Critically Endangered on the IUCN Red List, and also in common with the Pacific species it was described in the mid-19th century before being ‘lost to view’ for more than 100 years. Unlike Fiji Petrel, however, the nesting grounds, on the island of Reunion in the southwest Indian Ocean, have been identified from nocturnal surveys, although an actual nest has never been found, so much of the species’ breeding biology remains to be elucidated. Historically, its range was potentially wider, as subfossil remains attributed to Mascarene Petrel have been found on the nearby island of Rodrigues; much more recently, in September 2002, an individual was found dead in the Black River Gorges National Park, on Mauritius. As September is already close to the known breeding season on Reunion, estimated to occupy the period November to March, and birds start to visit the colonies as early as July, nocturnal surveys for Mascarene Petrel on Mauritius clearly should be undertaken. Mascarene Petrel is a uniformly dark seabird with a rather bulky bill, a gap between the raised tubenose and swollen bill tip, and blackish-brown plumage that is slightly paler on the chin and upper throat, while the undersides of the remiges have slightly silvery bases.

Uniformly dark petrel  with rather bulky bill  , gap between raised tubenose and swollen bill tip gives pinched appearance to middle of bill. Plumage blackish brown, slightly paler on chin and upper throat; under surface of remiges slightly silvery at bases. Sexes similar. Reminiscent of Bulweria but larger, shorter-tailed and lacks pale wingbar; resembles several dark petrels, especially longer-winged Trindade Petrel (Pterodroma arminjoniana), which breeds on nearby Round Island (1 Brooke, M. (2004). Albatrosses and Petrels Across the World. Oxford University Press, Oxford, UK. Close ); separated from Great-winged Petrel (Pterodroma macroptera) by slightly smaller size, less steep forehead and paler legs; large bill, uniform upperwing and all-dark, hardly contrasting underwing, are helpful features in its separation from other dark petrels, but some species are tricky; all-dark Puffinus shearwaters have more slender bills (especially tricky is dark-morph Wedge-tailed Shearwater Ardenna pacifica); Parkinson’s Petrel (Procellaria parkinsoni) slightly larger with two-tone bill. Juvenile probably similar to adult, but fledglings have narrower bills than adults (2 Le Corre, M., Ghestemme, T., Salamolard, M. and Couzi, F.X. (2003). Rescue of the Mascarene Petrel, a critically endangered seabird of Réunion Island, Indian Ocean. Condor 105(2):387–391. Close ). In light winds, flight consists of unhurried, regular zigzags along overall straight course, with glides low over water regularly alternatmg with low arcs and banks into breeze, usually accompanied by bursts of rather deep, slow flapping, while in moderate winds flight swifter with less zigzaging and progress in continuous smooth arc, with gradual ascents (never > 5 m above waves) and descents, only moderate tilts into wind, and soaring is interspersed every few seconds by short bursts of quicker and shallower wingbeats, thereby differing markedly from the “pendulum-like” or “roller-coaster” progression of many gadfly petrels in similar conditions (3 Attié, C., Stahl, J. C. and Bretagnolle, V. (1997). New data on the endangered Mascarene Petrel Pseudobulweria aterrima: a third twentieth century specimen and distribution. Colonial Waterbirds 20(3):406–412. Close ).

Separation from similar species was well covered by Shirihai et al. (4 Shirihai, H., T. Pym, and V. Bretagnolle (2015). Mascarene Petrels at sea off Reunion, Indian Ocean. Dutch Birding 37(2):109–115. Close ), from which the following is taken. At a distance, Mascarene Petrel has a highly elongated and more pointed rear body and tail than Great-winged Petrel Pterodroma macroptera, one of the two principal confusion species. These two species have identical plumage patterns, although on average Mascarene shows a darker frame to the underwing and tends towards a weaker upperwing pattern. However, structural features are more important and reliable. Mascarene lacks the deep-chested appearance of the latter species, giving it a more slender outline, with more slender and parallel-sided wings that have rounder tips, which features combine to afford the bird a ‘crucifix’ shape, unlike the ‘anchor’ shape of Great-winged, although the mode of flight can strongly affect the bird’s outline. Mascarene is 15–20% shorter winged, has a shorter overall length and is at least 50% lighter in mass, but these differences can be appreciated only in side-by-side comparison and with previous experience. In light winds, Mascarene appears less energetic and more lethargic than a typical Pterodroma, flying lower above the sea surface, with shallower and briefer arcs against the wind. It also has a squarer head profile, with an almost 90° forehead slope. The bill has a diagnostic structure, including well-developed latericorn and maxillary unguis with a very short, less pointed hook. The other main confusion species is Jouanin’s Petrel, against which Mascarene should appear larger and heavier, while its proportionately longer wings are frequently held stiffly and its flight is less erratic. Jouanin’s flies low above the water, zigzagging, changing height and direction more rapidly in shorter glides and arcs. It usually projects a sleeker impression, is faster moving, and has an even more streamlined rear, while its more angular wings, and elastic wing action result in an effortless flight impression. Mascarene has a relatively shorter, less graduated tail than Jouanin’s: the posterior body, behind wings, including the exposed tail comprises one-third of the bird’s total length, whereas in Jouanin’s it is about half. Mascarene lacks the pale panel on the greater upperwing-coverts, often shown by Jouanin’s, but this is a very variable feature, and some Jouanin’s have rather uniform upperwings. Their underwings are even more similar, but Mascarene can show stronger contrast, whereas Jouanin’s has a more uniform underwing. However, two plumage features may offer real distinctions, although both are subject to individual variation: Mascarene has a unique pattern of delicate, straw-yellow fine markings on the neck, and Jouanin’s often has a dull greyish, slate-blue hue on the head and/or neck, and often the upperparts, especially the scapulars.

Natal down

Undescribed

Juvenile

Like adult, except in bill proportions.

Adult

Entirely blackish brown, with silvery wash to underside of the remiges; chin and throat may be slightly paler than the rest of the head and body. Sexes similar.

No published information.

Bill

Black (1 Brooke, M. (2004). Albatrosses and Petrels Across the World. Oxford University Press, Oxford, UK. Close ).

Iris

Dark brown (1 Brooke, M. (2004). Albatrosses and Petrels Across the World. Oxford University Press, Oxford, UK. Close ).

Legs and Feet

Tarsi pink, and distal two-thirds of feet black with pale pinkish base to the inner toes (1 Brooke, M. (2004). Albatrosses and Petrels Across the World. Oxford University Press, Oxford, UK. Close , 5 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ).

Linear Measurements

Overall length 35–36 cm (6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close ) or 31–35 cm (7 Howell, S. N. G., and K. Zufelt (2019). Oceanic Birds of the World. Princeton University Press, Princeton, NJ, USA. Close ).

Linear measurements (in mm, means plus standard deviation, of seven specimens, from Attié et al. 3 Attié, C., Stahl, J. C. and Bretagnolle, V. (1997). New data on the endangered Mascarene Petrel Pseudobulweria aterrima: a third twentieth century specimen and distribution. Colonial Waterbirds 20(3):406–412. Close , and range and means of 22 specimens, Safford and Hawkins 5 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ):

Mass

160–270 (mean 209.6) g (2 Le Corre, M., Ghestemme, T., Salamolard, M. and Couzi, F.X. (2003). Rescue of the Mascarene Petrel, a critically endangered seabird of Réunion Island, Indian Ocean. Condor 105(2):387–391. Close , 5 Safford, R., and F. Hawkins, Editors (2013). The Birds of Africa. Volume 8. The Malagasy Region. Christopher Helm, London, UK. Close ).

Wingspan

84–90 cm (6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close , 7 Howell, S. N. G., and K. Zufelt (2019). Oceanic Birds of the World. Princeton University Press, Princeton, NJ, USA. Close ).

Considered by some authors to be race of Tahiti Petrel (P. rostrata) (8 Jouanin, C., and J.-L. Mougin (1979) Order Procellariformes. Pages 48-121 in Check-list of birds of the world, Volume 1, wecond edition (E. Mayr and G. W. Cottrell, editors). Museum of Comparative Zoology, Cambridge, Massachusetts, USA. Close ); external morphology and skeletal aspects indicate close relationship, but molecular data refute conspecificity (9 Bretagnolle, V., Attié, C. and Pasquet, E. (1998). Cytochrome-b evidence for validity and phylogenetic relationships of Pseudobulweria and Bulweria (Procellariidae). Auk 115(1):188–195. Close , 10 Gangloff, B., H. Shirihai, D. Watling, C. Cruaud, A. Couloux, A. Tillier, E. Pasquet, and V. Bretagnolle (2012). The complete phylogeny of Pseudobulweria, the most endangered seabird genus: systematics, species status and conservation implications. Conservation Genetics 13(1):39–52. Close ).

None.

Monotypic.

Réunion Island and surrounding seas; subfossil remains suggest that it formerly occurred on nearby Rodrigues (3 Attié, C., Stahl, J. C. and Bretagnolle, V. (1997). New data on the endangered Mascarene Petrel Pseudobulweria aterrima: a third twentieth century specimen and distribution. Colonial Waterbirds 20(3):406–412. Close ). An adult recorded on Mauritius in September 2002 (11 Tatayah, R.V., Jones, C.G., Birch, D. and Salamolard, M. (2011). First record of Réunion Black Petrel Pseudobulweria aterrima on Mauritius. Bulletin of the British Ornithologists' Club 131(1):64–66. Close ).

Very little known. Marine and probably pelagic; has been tentatively linked with cool waters. Breeds on inland cliffs and ravines within forest in mountainous parts of Réunion between 500 m and 1,150 m (12 Tatayah, R.V., Jones, C.G., Birch, D. and Salamolard, M. (2011). First record of Réunion Black Petrel Pseudobulweria aterrima on Mauritius. Bulletin of the British Ornithologists' Club 131(1):64–66. Close ,6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close ), with one record of an adult at 1,700 m (2 Le Corre, M., Ghestemme, T., Salamolard, M. and Couzi, F.X. (2003). Rescue of the Mascarene Petrel, a critically endangered seabird of Réunion Island, Indian Ocean. Condor 105(2):387–391. Close ).

Few data yet published, other than a single record from Mauritius of a roadkilled bird in Black River Gorges National Park in September 2002, although it has been suggested that this might indicate that P. aterrima breeds on the island (12 Tatayah, R.V., Jones, C.G., Birch, D. and Salamolard, M. (2011). First record of Réunion Black Petrel Pseudobulweria aterrima on Mauritius. Bulletin of the British Ornithologists' Club 131(1):64–66. Close ). A specimen, whose whereabouts were long unknown, said to have been collected alive by fishermen near Mumbai, in western India in June 1940 (13 Ripley, S. D. (1982). A Synopsis of the Birds of India and Pakistan together with those of Nepal, Bhutan, Bangladesh and Sri Lanka. Second edition. Bombay Natural History Society and Oxford University Press, Bombay, India; and Oxford, UK. Close ,14 Robertson, A.L.H. (1994). Occurrence of some pelagic seabirds (Procellariiformes) in waters off the Indian subcontinent. Forktail 10:129–140. Close ), has recently been traced to the Raffles Museum of Biodiversity Research, at the National University of Singapore, and its identity confirmed as the very similar Jouanin’s Petrel Bulweria fallax, which species was not described until the mid 1950s (15 Morioka, H., and C. M. Yang (1996). A catalogue of the bird specimens in the Singapore zoological reference collection. Raffles Bulletin of Zoology Supplement 4:1–141. Close ,16 Praveen J., and L. K. P. Kelvin (2013). Mascarene Petrel Pseudobulweria aterrima from Mumbai: a correction. Indian Birds 8(5):129–130. Close ,17 Praveen, J., R. Jayapal, and A. Pittie (2013). Notes on Indian rarities–1: Seabirds. Indian Birds 8(5):113–125. Close ). Nevertheless, a recent study using global location sensors found that Mascarene Petrels start their post-breeding dispersal on average in the first days of March, and return to their colonies around mid August; in between these times, the 14 birds that were tracked were mostly found over the Mascarene and Seychelles plateaux (n = 5), or in the Arabian Sea (n = 4), but two each migrated to the Bay of Bengal and the seas south of Sri Lanka, and the other moved as far as northwestern Australia (18 Saunier, M., J. Dubos, P. Pinet, L. Humeau, C. Caumes, P. Souharce, Y. Soulaimana Mattoir, M. Riethmuller, M. Le Corre, and A. Jaeger (2019). Phenology, at-sea distribution and activity of a critically endangered seabird, the Mascarene Petrel. Available from: https://www.researchgate.net/publication/336982873_Phenology_at-sea_distribution_and_activity_of_a_critically_endangered_seabird_the_Mascarene_Petrel [accessed Nov 18 2019]. Close ). In the seas around Réunion, the species has been recorded up to 1,320 km from the island during the period November–March (6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close ).

No information available, but has recently been observed scavenging at surface on floating offal (6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close ).

Whistling calls mentioned in literature (1 Brooke, M. (2004). Albatrosses and Petrels Across the World. Oxford University Press, Oxford, UK. Close ), with peak calling activity recorded between 25 December and 30 January, although it has been suggested that these dates can be attributed to unpaired males (6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close ). Calling generally commences around 20:00 hours, later than Tropical Shearwaters Puffinus bailloni breeding in the same mountains (6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close ).

Very few data available. Overall season approximately November–March (1 Brooke, M. (2004). Albatrosses and Petrels Across the World. Oxford University Press, Oxford, UK. Close ), but is present offshore from at least July–September (3 Attié, C., Stahl, J. C. and Bretagnolle, V. (1997). New data on the endangered Mascarene Petrel Pseudobulweria aterrima: a third twentieth century specimen and distribution. Colonial Waterbirds 20(3):406–412. Close ,6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close ), with incubation in December, while a bird recently photographed at sea in late December was believed to have an egg in the uterus and was presumably returning from pre-laying exodus (6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close ), and fledgings recorded 1 March–4 April suggesting incubation occurs October–December (6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close ). Breeding grounds went undiscovered until late 1990s; presumably nests in burrows in ground (perhaps also crevices) within dense vegetation on cliffs, although until November 2016 no nest had ever been found (BirdLife International 2017). Sometimes in small loosely spaced colonies (largest just four pairs), with a total of five breeding sites definitely known to harbour just 9–10 pairs.

CRITICALLY ENDANGERED. Recently rediscovered: known from ten specimens (most of them subsequently lost) taken in the 19th century, two more in the early 1970s, and a freshly dead bird found in January 1995 (3 Attié, C., Stahl, J. C. and Bretagnolle, V. (1997). New data on the endangered Mascarene Petrel Pseudobulweria aterrima: a third twentieth century specimen and distribution. Colonial Waterbirds 20(3):406–412. Close ), with a total of 26 birds thought to be of this species seen at sea around Réunion between 1978 and 1995 (3 Attié, C., Stahl, J. C. and Bretagnolle, V. (1997). New data on the endangered Mascarene Petrel Pseudobulweria aterrima: a third twentieth century specimen and distribution. Colonial Waterbirds 20(3):406–412. Close ). A total of 33 birds were observed at sea during the fourth week of December 2012 (6 Shirihai, H., T. Pym, M. San Román, and V. Bretagnolle (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. Close ), but many fewer during the same month in 2014 (19 Flood, R. L., E. Cook, M. Danzenbaker, D. Koch, J. Shemilt, and K. Zufelt (2015). Barau’s Petrel, Mascarene Petrel and other tubenoses off Réunion, Indian Ocean, in December 2014. Dutch Birding 37(5):295–301. Close ). Current population size estimated by BirdLife International to be just 100–200 mature individuals and is thought to be decreasing. However, data collected at sea during the period 1978–1995 suggested a population of c. 1,000 individuals (3 Attié, C., Stahl, J. C. and Bretagnolle, V. (1997). New data on the endangered Mascarene Petrel Pseudobulweria aterrima: a third twentieth century specimen and distribution. Colonial Waterbirds 20(3):406–412. Close ), or 45–400 pairs (1 Brooke, M. (2004). Albatrosses and Petrels Across the World. Oxford University Press, Oxford, UK. Close ), although subsequently it was felt that a total of 50 to 100 pairs was more likely, while a recent survey of the known breeding area found ten fledglings. Nevertheless, it remains true that several potentially suitable areas have not been surveyed. All of the known breeding areas occur within the boundaries of a proposed national park (2 Le Corre, M., Ghestemme, T., Salamolard, M. and Couzi, F.X. (2003). Rescue of the Mascarene Petrel, a critically endangered seabird of Réunion Island, Indian Ocean. Condor 105(2):387–391. Close ). Eggs, chicks, and perhaps also adults are likely to suffer predation by feral cats (Felis catus), dogs and rats (Rattus), as well as by the introduced Small Indian Mongoose Herpestes javanicus (12 Tatayah, R.V., Jones, C.G., Birch, D. and Salamolard, M. (2011). First record of Réunion Black Petrel Pseudobulweria aterrima on Mauritius. Bulletin of the British Ornithologists' Club 131(1):64–66. Close ); local people may take some for food (shearwaters are commonly eaten on Réunion). The other major factor is widespread light pollution, such as from street lamps and sport installations, which is responsible for considerable light-induced petrel mortality on the island—eight P. aterrima (four of them just fledged) have been recovered having been attracted to lights, one of which died while the others were successfully released (2 Le Corre, M., Ghestemme, T., Salamolard, M. and Couzi, F.X. (2003). Rescue of the Mascarene Petrel, a critically endangered seabird of Réunion Island, Indian Ocean. Condor 105(2):387–391. Close ); since 1996, there has been a campaign to quantify this mortality and to rescue as many birds as possible, with more than 90% of the petrels (of various species) found having being successfully released (20 Le Corre, M., A. Ollivier, S. Ribes, and P. Jouventin (2002). Light-induced mortality of petrels: a 4-year study from Réunion Island (Indian Ocean). Biological Conservation 105(1):93–102. Close ). The bird recently found dead on Mauritius was probably also a victim of such light-induced mortality (12 Tatayah, R.V., Jones, C.G., Birch, D. and Salamolard, M. (2011). First record of Réunion Black Petrel Pseudobulweria aterrima on Mauritius. Bulletin of the British Ornithologists' Club 131(1):64–66. Close ). Pesticide residues could be significant, as in the case of the Trindade Petrel Pterodroma arminjoniana at neighboring Mauritius. The location of additional breeding areas is of immediate priority, followed by evaluation of numbers, major threats, and conservation requirements.