Justification of Red List Category
This species qualifies as Critically Endangered as it has undergone an extremely rapid historical decline over three generations. The on-going declines appear to have ceased and the population is slowly recovering thanks to intensive conservation work, which may lead to the downlisting of this species in the future.
In 2012, the total population was estimated to number around 150-200 individuals, including 80-100 mature individuals (G. Taylor in litt. 2012).
Although intensive conservation management (predator control in particular), appears to have allowed the population to increase slowly since the late 1990s, the species has undergone a severe decline over the last century, in excess of 80% over the last 60 years (c. three generations). The species is very long-lived with two birds first captured as adults in October 1982 still breeding in 2015 (G. Taylor and D. Boyle pers. comm. 2016)
Pterodroma magentae was rediscovered in 1978 in the south-west corner of Chatham Island, New Zealand, 111 years after it was first collected at sea (Crockett 1994). Its prevalence in Moriori middens suggests it was once common and has undergone a massive historical decline (Imber et al. 2005). In 1994, only four breeding pairs were known, although it was suspected that others remained undetected, and that the population was still declining at this time. In 2004, surveys indicated a population of 120 individuals, including 15 breeding pairs (Hilhorst 2000, Brooke 2004, G. Taylor in litt. 2005). Just 16 chicks were known to have fledged from 1987-1988 to 2000 (Taylor 2000), but in 2002, a total of seven chicks were fledged (M. Ogle in litt. 2002). By 2006, there were 35 active burrows, an estimated 25 breeding pairs, and 11 known chicks, taking the total number of chicks fledged since 1987 to 63 (Stephenson 2006b). A total of 17 pairs were believed to have laid in the 2009/2010 breeding season (C. Miskelly in litt. 2008, 2010).
Between 2007 and 2011, a total of 59 chicks were successfully moved from the Tuku Nature Reserve in the south of Chatham Island to the nearby Sweetwater Conservation Covenant, where they all successfully fledged (Miskelly et al. 2009, G. Taylor pers. comm. 2016). Inshore waters (1-2 km offshore from the colony) around Otawae Point are thought to be important for non-breeders visiting the colony and during courtship at night (Imber et al. 2005). Its range at sea is known to extend across the entire South Pacific Ocean from the Tasman Sea to South America, based on recent tracking results using geolocators from 2008 to 2012 (G. Taylor in litt. 2016). During the breeding season, birds feed mainly south and south-east of the Chatham Islands; they then disperse widely during the non-breeding season, ranging from Tasman Sea to the west coast of South America (G. Taylor in litt. 2012).
It breeds in a fragmented colony under dense forest (Heather and Robertson 1997), 4-6 km inland. Burrows are up to 5 m long and breeding takes place from September to May (Taylor et al. 2012). Males occupy burrows for 1-3 years before pair formation and breeding; non-breeding females rarely visit the colony (Imber et al. 2005). Its diet is not well known, but includes squid (Imber et al. 1995) and fish (G. Taylor in litt. 2012). Recent ringing returns show that males return to the colony aged 3-10 years, females at 4-9 years, and first breeding is attempted at around five years of age (Department of Conservation 1999, Imber et al. 2005, G. Taylor in litt. 2012). The pairs form a life-long bond, one egg is laid per year, incubated by both parents, and fledging chicks climb trees from which they launch themselves to fly out to sea (C. Miskelly in litt. 2008, 2010).
Introduced species have previously represented the largest threat to this species, with pigs, cats and dogs predating adults and many other species, such as rats, hedgehogs, Weka and possums depredating nests and causing a loss of reproductive success. Intensive predator control efforts have dramatically reduced the incidence of predation, and the population is currently increasing due to these efforts. This includes poisoning and trapping for all rodents, the maintenance of cat trapping lines around all burrow clusters, removing 50-70 cats annually (Chatham Island Taiko Trust), and the use of pig-hunting dogs which, although identified as a threat themselves (Aikman and Miskelly 2004), are unlikely to be able to access the whole colony and have not been implicated in species mortality in recent years. This work is essential, and cessation of these actions would see population declines once again. Introduced livestock such as sheep and cows have previously caused habitat degradation however, livestock are now fenced out of the Tuku Nature Reserve, where almost all of the species breed. Habitat degradation is therefore limited to areas in which the petrel is effectively already extinct, but livestock presence prevents the regeneration of suitable habitat for the species.
This species is vulnerable to flooding, which is thought to lower breeding success in some seasons (Taylor 2000). Longer term climate change impacts on oceans, such as acidification, may also become a threat.
Molecular analysis has found that, while the sex-ratio is approximately even in petrel chicks and breeding adults caught on the ground, 95% of non-breeding adults are male. This suggests that low population levels may be causing unpaired male birds difficulty in attracting a mate, as their calls are too spread out to attract the infrequent females which pass by (Lawrence et al. 2008a).In the past, the Magenta Petrel has been subjected to a form of large-scale harvesting called ‘muttonbirding’ which is likely to have contributed to the population decline experienced by this species, however, this no longer occurs and is highly unlikely to return.
Conservation Actions Underway
Ten years of intensive searching led to its rediscovery in 1978, but no burrows were found (Crockett 1994). In 1987, radio-transmitters attached to the tail-feathers of birds finally led to the discovery of three burrows (Imber et al. 1994b), and trapping for predators was immediately commenced (Imber et al. 1994a). Invasives control is ongoing for a range of different species, and cessation of these actions would see population declines once again. On-going searches located only three more burrows, but in 1999, at least 17 new burrows were discovered (Taylor 2000). Breeding areas have been protected by the Tuku Nature Reserve (Stephenson 2006a). Predator control was intensified in 1996 (Imber et al. 2005). All burrows are monitored annually for breeding attempts (Imber et al. 1994a, Taylor et al. 2012) and sometimes infra-red cameras are deployed at each nest to monitor activity and identify predators (Johnston et al. 2003). Since 2007, burrows have been monitored using automated PIT-tag readers, and most birds caught since 2001 have been fitted with PIT-tags (Taylor et al. 2012). Egg- and chick-rearing trials have been undertaken on the closely-related Grey-faced Petrel P. macroptera, and its diet analysed, to develop methods for captive rearing of P. magentae (Taylor 2000). The Chatham Island Taiko Trust was established in 1998 to provide legal status to the continuing work (Department of Conservation 2007), and has since provided substantial funding to much of the conservation work focussed on this species (M. Bell in litt. 2012). In 2006, a 3-ha safe colony with predator-proof fence, wooden burrows, and playback sound system was established at the Sweetwater Secure Breeding Site, and chicks have been transferred here prior to fledging to form a new colony (Taylor 2000, Stephenson 2006b). Eight chicks were successfully moved and fledged here in April-May 2007, as were a further 13 in 2008 and 13 in 2009 (C. Miskelly in litt. 2008, 2010). Over five summers, 58 chicks were transferred from Tuku Nature Reserve to Sweetwater (Chapman 2014). A chick that fledged in 2007 returned to Sweetwater in 2010, this was followed by another chick in 2011 and 12 chicks in 2012. The first two cohorts of chick transfers had a survival rate of approximately 60% (considerably higher than the 20-30% natural recruitment rate [Chapman 2014]). Birds bred at Sweetwater in 2013, with two eggs laid (Chapman 2014). The 1,200-hectare South Chatham Covenant, adjacent to the Tuku Nature Reserve and containing one known cluster of burrows, is now fenced, and is currently being surveyed to determine its actual area: as at Sweetwater ownership will remain with the existing landowners but the Covenant will ensure protection in perpetuity (C. Miskelly in litt. 2008, 2010). The 2011 target is to establish a self-sustaining population of at least 250 individuals. Birds have been fitted with geolocators since 2008/2009 (G. Taylor in litt. 2012). A recent conservation action has been to catch birds through the use of spotlights and trained petrel dogs to locate additional burrows and attempting to introduce known females to burrow clusters that contain unpaired males (G. Taylor in litt. 2012). This action has resulted in 6 successful new pairings (G. Taylor pers. comm. 2016). Passive Integrated Transponder (PIT) readers are used at Sweetwater to monitor breeding burrows (Chapman 2014).
Conservation Actions Proposed
Continue ground and dog searches and telemetry to locate further burrows, as well as night surveys for prospecting birds and to collect data on survival. Continue to use study holes at all active nest burrows to enable active intervention if chicks are undernourished or abandoned. Continue sustained predator and herbivore control. Continue to study the species's ecology, including its at-sea distribution. Consider maintenance of genetic diversity when planning future conservation actions (Lawrence et al. 2008b). Continue to translocate chicks to Sweetwater Conservation Covenant to build up secure population (M. Bell in litt. 2012).
38 cm. Medium-sized, dark brownish-grey and white petrel. Mostly uniform brownish-grey head, neck, upper breast, upperparts, upperwing, tail. White lower breast, belly, undertail. Brown underwing, paler under primaries. Black bill. Pink legs. Feet pink proximally, black distally. Similar spp. Phoenix Petrel P. alba is smaller, more brown. Atlantic Petrel P. incerta is bulkier with brown undertail. Voice Calls or-wik, si, si, si and orr.
Text account compilers
McClellan, R., Moreno, R., Pilgrim, J., Stuart, A., Symes, A., Taylor, J., Bird, J., Benstead, P., Ashpole, J, Calvert, R., Fjagesund, T., Hermes, C., Lascelles, B., Martin, R.
Ogle, M., Miskelly, C., Taylor, G.A., Bell, M., Lawrence, H.
BirdLife International (2020) Species factsheet: Pterodroma magentae. Downloaded from http://www.birdlife.org on 30/09/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 30/09/2020.