Leader (2011) recommended that, due to differences in plumage and structure, Apus pacificus should be split into four separate species:
Pacific Swift Apus pacificus with subspecies kurodae Sálim Ali's Swift Apus salimali Blyth's Swift Apus leuconyx Cook's Swift Apus cooki.
Subsequently, Päckert et al (2012), during a study designed to provide a wider molecular phylogeny of Old World swifts, found through molecular analysis that cooki is more closely related to Dark-rumped Swift Apus acuticauda than to Apus pacificus pacificus. They refrained from giving particular taxonomic recommendations due to limitations of sampling and suggested more genetic research needs to be carried out on the other forms currently assigned within Apus pacificus.
Dickinson & Remsen (2013) suggested that there may be some doubt regarding Leader's use of kurodae in preference to kanoi.
Pending further research and clarification, we retain the 'traditional' classification here.
Refs:
Leader, P.J., (2011) Taxonomy of the Pacific Swift
Apus pacificus
Latham, 1802,complex. Bull. Brit. Ornithol. Club 131, 81–93.
Päckert, M., Martens, J., Wink, M., Feigl, A. & Tietze, D.T. (2012) Molecular phylogeny of Old World swifts (Aves:
Apodiformes, Apodidae, Apus and Tachymarptis) based on mitochondrial and nuclear markers. Molecular
Phylogenetics and Evolution 63: 606‐616.
Dickinson, E.C. & Remsen, J. V. Jr. (2013) The Howard & Moore Complete Checklist of the Birds of the World. Vol. 1 Non-passerines. (4th edn.)
