LC
Blue Petrel Halobaena caerulea



Justification

Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
Brooke (2004) estimated the global population to number at least 3,000,000 individuals.

Trend justification
Analysis of the proportion of Blue Petrels in skua diets by Cerfonteyn and Ryan (2016) suggests that despite the initial rapid increase in breeding success, petrel numbers on Marion Island have not substantially recovered following the eradication of cats there in 1991. It is possible that recovery rates are being negatively affected by the predation of chicks and eggs by introduced house mice (Mus musculus) (Dilley et al., 2017). Additionally, surveys by Pacoureau et al., (2019) found evidence of a long-term decline in burrow occupancy of Blue Petrels at Mayes Island, Kerguelen, with a 70% reduction in burrow occupancy between 1992 and 2013. The Prince Edward Islands, which encompasses Marion Island, and the Kerguelen archipelago are thought to support a substantial proportion of the global population (Dilley et al., 2017), and therefore the overall population trend is suspected to be declining.

Distribution and population

The Blue Petrel is found throughout southern Oceans. Breeding sites include the Crozet Islands and Kerguelen Island (French Southern Territories), Marion Island and Prince Edward Island (South Africa), Macquarie Island (Australia) and South Georgia (Georgias del Sur). Adults are perhaps mainly sedentary, though young birds are more dispersive (del Hoyo et al. 1992).

Ecology

Breeding begins in September, occuring in colonies where it nests in long burrows excavated in soft soil under grass tussocks (del Hoyo et al. 1992). Foraging during the chick-rearing period at the Kerguelen Islands involves regular alternation between short trips in the vicinity of the island and long trips to Antarctic waters. Short trips enable an increase of chick-feeding frequency at the expense of energy reserves built up during long trips. Diet comprises of crustaceans (especially krill), fish, squids and some insects (del Hoyo et al. 1992, Cherel et al. 2002). The highest recorded blue petrel burrow in surveys by Dilley et al., (2019) was found at an elevation of 200m.

Threats

Impacts of rat and cat predation appears severe and cats appear to have contributed to or caused the extirpation from several islands (Carboneras et al. 2020). The eradication of cats on Marion Island in 1991 initially resulted in a rapid increase in breeding success (Cooper et al. 1995), however evidence now suggests that the population still hasn't fully recovered since the extirpation of cats (Cerfonteyn and Ryan, 2016). Since the removal of cats on Marion Island, it is now thought possible that the impacts of chick and egg predation by introduced house mice Mus musculus is hampering population recovery (Dilley et al., 2017). The European Rabbit may also severely impact Blue Petrels on the islands where it is present, shown by the eight-fold increase in Blue Petrel population on Ile Verte within six years of rabbit eradication (Brodier et al. 2011). Habitat degradation by the native Antarctic Fur Seals on South Georgia, which have dramatically increased in the past decades, causes the loss of breeding sites and also may cause the loss of nests (Prince & Croxall 1996).

Conservation actions

Conservation Actions Underway
Cats were eradicated on Marion Island in 1991, which led to an increase in Blue Petrel breeding success (Cooper et al. 1995). European Rabbits were eradicated on Ile Verte in 1992, which was followed by an increase in Blue Petrel population within six years of the eradication Brodier et al. 2011).

Conservation Actions Proposed
Research into the extent of nest predation by introduced house mice Mus musculus on petrel breeding success (Cerfonteyn and Ryan, 2016) .

Acknowledgements

Text account compilers
Clark, J.

Contributors
Fjagesund, T., Hermes, C., Stuart, A. & Newton, P.


Recommended citation
BirdLife International (2022) Species factsheet: Halobaena caerulea. Downloaded from http://www.birdlife.org on 17/08/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/08/2022.