Current view: Data table and detailed info
Taxonomic note
Puffinus newelli (del Hoyo and Collar 2014) has been split into P. newelli and P. myrtae (which see) (Handbook of the Birds of the World and BirdLife International 2018). Martínez-Gómez et al. (2015) found molecular evidence that Newell’s Shearwater Puffinus newelli and Townsend’s Shearwater P. auricularis are conspecific. Although they mention the morphological analysis in del Hoyo and Collar (2014: p386) which gave a Tobias score of 7 to newelli, these authors did not consider the characters in question: larger size (an effect size of 3.29 on tail length yielded a score of 2; new data in Shirihai et al. [2017] yields an effect size of 2.41, thus again a score of 2); cleaner-cut head pattern (score 1); bolder, squarer neck mark (score 2); all-white undertail-coverts (score 2); plus darker upperparts (scored 1 but uncounted).
(These characters and scores are revised below.)
Martínez-Gómez et al. (2015) also mentioned that ‘Howell (2012) proposed a separate treatment based on their differences in morphology, breeding chronology (Ainley et al. 1997; Bourne et al. 1988), and breeding ecology (Spear et al. 1995)’ [NB these citations in quotation marks are not in the reference list below]. Thus it appears that there are behavioural and ecological differences between the taxa in addition to the morphological ones. Martínez-Gómez et al. (2015) cited the case of Charadrius dealbatus as one in which morphological characters are strong but genetic ones non-existent, but they did not mention that del Hoyo and Collar (2014) accepted the morphological characters despite the genetic evidence. In the present case it seems appropriate to continue to consider that two species are involved, pending confirmation of the authors’ molecular work, clarification of the accuracy of the scoring used to maintain the split of newelli in del Hoyo and Collar (2014), and evidence of the behavioural and ecological differences between the taxa.
However, Martínez-Gómez et al. (2015) also found that P. n. myrtae, ‘Rapa Shearwater’, is genetically more distinct from newelli than newelli is from auricularis. On this basis they propose that myrtae be treated as a full species. Such an arrangement is supported by Shirihai et al. (2017), who noted:
Rapa Shearwater is much smaller (in all biometric characters) than the other two taxa…, and is furthermore highly distinctive in having a unique combination of white undertail-coverts (vs. dark in both newelli and auricularis) and whitish inner webs to the remiges, as well as a white face.
There is a contradiction here with del Hoyo and Collar (2014), where the undertail-coverts of newelli, compared to auricularis, are given as ‘white vs white-edged grey’. Further consideration of this point, by examining images online and Plate 16.1 in Howell (2012: 147), indicate that auricularis has marginally more extensive black undertail-coverts than newelli. However, the information contained in Howell (2012) and the references he cited, plus that conveyed in Howell’s Plate 16.1, lead to somewhat differently scored and parsed characters for newelli vs auricularis: larger size (effect size 2.41 [see above]: 2); cleaner-cut and blacker head- and neck-sides (2); more white on undertail-coverts (1); darker upperparts (1); somewhat different feeding ecology, using less upwelled, more stratified waters with more turbulent meteorological features (Spear et al. 1995; allow 1); breeding chronology (Ainley et al. 1997; no score allowed).
By this means newelli continues to achieve species rank under the Tobias criteria. We therefore retain P. newelli as a separate species from P. auricularis until independent genetic analysis supports Martínez-Gómez et al. (2015) and/or until a new full assessment of morphological characters, and of the behavioural/ecological evidence, can be undertaken.
Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Handbook of the Birds of the World and BirdLife International. 2018. Handbook of the Birds of the World and BirdLife International digital checklist of the birds of the world. Version 3. Available at: https://datazone.birdlife.org/userfiles/file/Species/Taxonomy/HBW-BirdLife_Checklist_v3_Nov18.zip.
Howell, N. G. 2012. Petrels, Albatrosses, and Storm-Petrels of North America: A Photographic Guide. Princeton University Press, Princeton, New Jersey, USA.
Martínez-Gómez, J. E., Matías-Ferrer, N., Sehgal, R. N. M. & Escalante, P. 2015. Phylogenetic placement of the critically endangered Townsend’s Shearwater (Puffinus auricularis auricularis): evidence for its conspecific status with Newell’s Shearwater (Puffinus a. newelli) and a mismatch between genetic and phenotypic differentiation. J. Orn. 156: 1025-1034.
IUCN Red List criteria met and history
Red List criteria met
Red List history
| Migratory status |
full migrant |
Forest dependency |
medium |
| Land-mass type |
|
Average mass |
- |
Population justification: There have been several population size estimates for this species (see Griesemer and Holmes 2011), but the most recent gives a minimum population estimate of 27,011 individuals (Joyce 2016), which roughly equates to 18,000 mature individuals. However, given the decline on Kauai and near extirpation from Maui, the population size could now be far smaller (D. Ainley in litt. 2016). The population size is therefore precautionarily placed in the band 10,000-19,999 mature individuals.
Trend justification: Once abundant, the species has undergone rapid declines in historic times due to overhunting and predation by introduced mammals and was believed to be extinct by 1908, before it was rediscovered in 1947 (Ainley et al. 1997). Radar survey data has shown that, since the hurricane Iniki hi Kaua'i in 1992, the number of individuals on the island may have declined by as much as 93.5% between 1993 and 2013, driven by key threats such as introduced predators, light attraction, collisions with powerlines and habitat alteration (Raine et al. 2017). It is considered that potentially 90% of the global population is from Kaua`i (see Griesemer and Holmes 2011). Using the minimum population estimate of 27,000 individuals (Joyce 2016), and assuming that trends for individuals breeding on other islands are stable, the population declines at >99% over three generations (46.5 years). It is uncertain whether the rate of decline has been consistently that high over the past three generations, though. Without targeted conservation work against the key threats to the species, it is plausible though that such declines may continue into the future.
Country/territory distribution
Important Bird and Biodiversity Areas (IBA)
Recommended citation
BirdLife International (2024) Species factsheet: Newell's Shearwater Puffinus newelli. Downloaded from
https://datazone.birdlife.org/species/factsheet/newells-shearwater-puffinus-newelli on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.
