Little Shearwater Puffinus assimilis


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). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very 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
Based on data reviewed by Brooke (2004), the global population is thought to number over 100,000 pairs, assumed to equate to over 200,000 mature individuals. Thus, the population is placed in the band 100,000-499,999 mature individuals. The total population is therefore assumed to number c.300,000-750,000 individuals.

Trend justification
The population is suspected to be in decline owing to predation by invasive species.

Distribution and population


Predation by introduced rats Rattus spp. and feral cats Felis catus represents the greatest current and future threat, due to their presence across large portions of the species's breeding range in New Zealand and Australia. There is suggestive evidence that rat predation has resulted in previous local extinctions of Little Shearwaters on some South Pacific Islands. Rat predation affects different subspecies differently, and there is a risk that some races (Puffinus assimilis assimilis in particular) may become locally extinct in the future. The continued presence of non-native predators on many islands is likely a contributory factor to preventing recolonisations. The species is listed as Vulnerable in Australia primarily due to predation by invasive species (Brooke 2004). The species is also directly persecuted and hunted for its eggs, meat and for use as fish bait in parts of the range. Although this harvest only affects a minority of the population at present, it should be regarded as a future focus for conservation efforts (Onley and Scofield 2007).


Text account compilers
Miller, E., Fjagesund, T., Symes, A., Taylor, J., Martin, R.

Recommended citation
BirdLife International (2021) Species factsheet: Puffinus assimilis. Downloaded from on 19/01/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from on 19/01/2021.