|Scientific Name:||Pterodroma magentae|
|Species Authority:||(Giglioli & Salvadori, 1869)|
|Red List Category & Criteria:||Critically Endangered A2ce ver 3.1|
|Reviewer/s:||Butchart, S. & Symes, A.|
|Contributor/s:||Bell, M., Lawrence, H., Miskelly, C., Ogle, M. & Taylor, G.|
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.
|Range Description:||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 are 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 (C. Miskelly in litt. 2008, 2010). 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 in 2008/2009 and 2010/2011 (G. Taylor in litt. 2012). 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).|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||In 2012, the total population was estimated to number around 150-200 individuals, including 80-100 mature individuals (G. Taylor in litt. 2012).|
|Habitat and Ecology:||
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 (C. Miskelly in litt. 2008, 2010). 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 (Heather and Robertson 1997) 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 (particularly three rat species, pigs, cats, Weka, possums and stray dogs [Johnston et al. 2003, Imber et al. 2005]) take eggs, chicks and adults, or compete for, destroy or cause the desertion of burrows. Flooding of burrows may also lower breeding success (Taylor 2000). Loss of forest habitat from accidental fire represents a threat (Aikman et al. 2001). Historically, the pastoralisation of Chatham Island probably caused the final destruction of the major colonies. Prior to 1900, local Moriori and Maori caught thousands of chicks for food (Crockett 1994, Stephenson 2006b). 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). There are no at-sea threats that are known to be seriously and imminently impacting this species (G. Taylor in litt. 2012). Some closely related species have been caught on long-lines, thus there may be impacts on this species. Longer term climate change impacts on oceans, such as acidification, may also become a threat. Its highly dispersed non-breeding movements lower risks to the species of localised threats such as oil spills (G. Taylor in litt. 2012).
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). 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 for breeding attempts (Imber et al. 1994a, Department of Conservation 1999) 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 all birds have been fitted with PIT-tags (Taylor et al. in press). 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). 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 to locate additional burrows and attempting to introduce known females to burrow clusters that contain unpaired males (G. Taylor in litt. 2012).
Conservation Actions Proposed
Continue ground 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).
|Citation:||BirdLife International 2012. Pterodroma magentae. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 25 May 2013.|
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