Justification of Red List Category
This species is classified as Critically Endangered because it is assumed to have an extremely small breeding population and to be undergoing a continuing decline owing to predation and light-induced mortality. Effective conservation measures are urgently needed.
From their at-sea counts, Attie et al. (1997) suggest that the population may be around 1,000 individuals, implying 250 (45-400) breeding pairs, although 50-100 pairs was considered more likely (V. Bretagnolle in litt. 1999), i.e. 100-200 mature individuals. However, recent estimates indicate that the breeding population may be just a few dozen pairs (Tatayah et al. 2011). The recent sighting of 33 different individuals in 3 days at sea south of Reunion Is suggest that an unknown breeding population may exist somewhere, and that a more likely breeding population size is 100 pairs (Shirihai et al. 2014).
Suspected to be declining owing to predation and light-induced mortality.
Pseudobulweria aterrima is endemic to Réunion Island (to France). A subfossil mandible have been found in Rodrigues (Mauritius) and a dead bird have been found in Black River National Park, Mauritius (Tatayah et al. 2011), but there is no evidence that the species breed elsewhere than in Réunion Island.
The Mascarene Petrel, like the 3 other species of petrels and shearwaters of Réunion Island, is attracted by urban light. Attracted birds fall to the ground and would die if not rescued. The phenomenon was discovered in 1996 (Le Corre et al. 2002, 2003), and since then, an island-scale rescue campaigns resulted in the finding of 45 birds, among which 42 where banded and released successfully (Riethmuller et al. 2012, SEOR and LIFE+ Project unpublished data). Twenty of these rescued birds were fledglings attracted by light while on their maiden flight to the sea. These findings are currently the only direct evidence that the species still breed successfully at Réunion Island.
A National Action Plan was written in 2012 by Riethmuller et al. (2012) and currently, there is an LIFE + programme ongoing (see hereafter). Based on acoustic surveys, the species is known to breed at several places of the central part of Réunion Island between 500 and 1500 meters above sea level (mostly at Grand Bassin, commune of le Tampon and Entre Deux). All fledglings have been found in February, March and April, suggesting a seasonal breeding during austral summer. Nevertheless, the suspected breeding places are currently out of reach, which prevent any detailed estimation and study of the population.
Five breeding areas were described in 2001 (9-10 pairs in total, including one loose colony with four pairs), all restricted to a small area which is unlikely to harbour more than c. 40 breeding burrows in total (V. Bretagnolle in litt. 1999, 2005). Nevertheless, there has no been confirmation and/or recent surveys of such breeding areas and its exact location remains unpublished. Calls have been heard during the breeding season (austral summer) on cliffs at 1,000 m and fledglings have been caught in March (Tatayah et al. 2011). It is possible that they nest in mountain parts of the Black River Gorges, as the habitat is similar to that of their suspected nesting areas on Réunion (Tatayah et al. 2011).
All presumed breeding sites are on cliffs, presumably in healthy vegetation. Recent information confirms austral summer breeding, with laying around December, and fledging between February and March (Riethmuller et al. 2012).They are thought to return to nest sites nocturnally to reduce chances of predation (Tatayah et al. 2011). The species feeds at the surface (Shirihai et al. 2014).
Like the threatened Barau's Petrel Pterodroma baraui (also endemic to Réunion), the main threats are likely to be predation by feral cats and rats (Riethmuller et al. 2012) and urban light-induced mortality which mainly affects inexperienced juveniles (Le Corre et al. 2002). Thirty birds have been found stranded apparently after being attracted by light between 1996 and 2011; 28 were released successfully and two died (Le Corre 1999, Le Corre et al. 1999, M. Le Corre in litt. 1999, Le Corre et al. 2003, M. Riethmuller et al. 2012). Widespread light pollution such as street lamps and sport installations are responsible for the greatest majority of light-induced petrel mortality on Réunion (Le Corre et al. 2002, Le Corre et al. 2003); the roadkill specimen on Mauritius is further evidence of the problem (Tatayah et al. 2011). Light-induced mortality of the juveniles of this rare petrel is likely to affect the long-term population dynamics but their longevity will cause a lag before real population declines are identified (Le Corre et al. 2002). The feeding behaviour of the species makes it vulnerable to fishing activities (Shirihai et al. 2014). Pesticide residues may also pose a threat (Carboneras et al. 2014).
Conservation Actions Underway
Since 1996, there has been a campaign to quantify urban light-induced mortality and to rescue as many birds as possible (Le Corre 1999, Le Corre et al. 1999, Le Corre et al. 2002). The rescues have been successful, with over 90% of the petrels (of various species) found on Réunion being released again (Le Corre et al. 2002). From 1996-2002, a public appeal aimed at rescuing downed birds produced eight petrels, of which seven were banded and released (Le Corre et al. 2003). One ringed individual Mascarene Petrel released after being rescued has been resighted alive several years later (Riethmuller et al. 2012). La Société d'Études Ornithologiques de la Réunion is working in partnership with EDF Réunion to reduce light pollution on Réunion (Bizien 2013). Surveys have identified the location and characteristics of the breeding area, however, no concerted attempts have been made to assess the impact of introduced predators and predator control has not been trialled (V. Bretagnolle in litt. 2005, Riethmuller et al. 2012). A series of expeditions to remove rats from around one of the last breeding colonies of this species on Réunion was launched in August and September 2014 (Jan and Fouillot 2014). Cat control measures have also been introduced around colonies. A LIFE-funded project from 2014 to 2020 aims to limit the decline of Mascarene and Barau's Petrels through techniques including: the development of appropriate conservation actions, predator control in remote areas, awareness-raising, and improving ecological knowledge of these species (LIFE+ PETRELS 2014). Massive prospecting efforts, using innovative or demonstrative tools including infrared binoculars, sniffer-dogs, VHF and 5g Argos tags and acoustic survey with Song Meter, are engaged to discover the breeding colonies.
Conservation Actions Proposed
Continue conservation actions engaged in the LIFE+ PETRELS Project for known breeding areas, and execute predators trapping and rat control, legal protection and monitoring of at least one or two burrows. Continue rescue programme of young birds attracted by lights (M. Le Corre in litt. 1999, Le Corre et al. 2002). Investigate light-reduction programmes either through light-shielding or light restriction during the fledgling period (Le Corre et al. 2002). Continue to search for further breeding grounds and, once found, evaluate population numbers, major threats and conservation action required (M. Le Corre in litt. 1999, Le Corre et al. 2002). Install an artificial breeding colony to create a suitable area free of predators, and display Mascarene Petrel throughout the night during the breeding season to encourage individuals to recolonize these sites.
36 cm. Medium-sized, dark gadfly petrel. Dark chocolate-brown with slightly paler chin, upper throat and underwing. Black bill. Pink tarsi. Black feet, webs with pale patch towards base of inner web. Similar spp. Like Bulwer's Petrel Bulweria bulwerii and Jouanin's Petrel B. fallax but more robust, smaller with heavier bill, shorter tail and lacking wing-bar. Dark phase of Trindade Petrel Pterodroma arminjoniana has longer wings. Great-winged Petrel Pterodroma macroptera has a larger wingspan with a longer, more pointed 'hand' it is stockier in appearance with a large, rounder head and broader rear (Shirihai et al. 2014).
Text account compilers
Ashpole, J, Butchart, S., Lascelles, B., Bird, J., Moreno, R., Anderson, O., Symes, A., Ekstrom, J., Martin, R, Tarzia, M, Stattersfield, A.
Riethmuller, M., Dubos, J., Pinet, P., Lequette, B., Bretagnolle, V., Le Corre, M.
BirdLife International (2018) Species factsheet: Pseudobulweria aterrima. Downloaded from http://www.birdlife.org on 23/09/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/09/2018.