Prolegomenon to further studies in the Chrysococcyx 'Malayanus' group (Aves, Cucilidae)

In its present state, the corpus of knowledge constituting our understanding of the Chrysococcyx 'malayanus' group is too unorganized to be used directly as the foundation for a modern systematic appraisal. A n attempt is here made to rectify this by overhauling the available facts. Stemming from this exercise, a few simple preliminary adjustments to the nomenclature and taxonomy of the group are suggested. The taxa here recognized are C. minutillus (with subspecies peninsularis subsp. nov., albifrons, cleis subsp. nov., minutillus and barnardi), C. russatus (subspecies aheneus, jungei, misoriensis and russatus), C. rufomerus, C. crassirostris and C. ruficollis. The type description of Cuculus malayanus Raffles, 1822 being recognizable as a femalephase Chrysococcyx x. xanthorhynchus (Horsfield, 1821), C. 'malayanus' becomes known as C. minutillus Gould, 1859, the next available name. Chalcococcyx niewenhuisi Vorderman, 1898 is transferred from the synonymy of C. crassirostris to that of C. minutillus. Chalcococcyx poecilurus Gray, 1862 is disassociated from the populations currently under this name (hereafter called C. russatus misoriensis) and held in abeyance as a nominal taxon whose reality and relationship to misoriensis require further investigation. The records of 'malayanus' from Cambodia and Cochinchina are questioned. Those from the Philippines are also examined: whereas the extant specimens are all referable to the Bornean form C. russatus aheneus, most of the unsupported records are judged from their descriptions to have been based on female-phase C. xanthorhynchus amethystinus. A n aheneus-like indivudual netted on the crest of the Main Range in Malaya indicates a situation requiring further study. C. m. minutillus is not known to breed outside northern Australia. Records of this form from the Lesser Sundas, the Moluccas, Celebes (Peleng I.) and southern New Guinea (Utanata R.) are here regarded as being of non-breeding visitors; the holotype of niewenhuisi from Halmahera is presumed to have been one such. C. m. barnardi and the southern populations of C. r. russatus are also migratory ; one specimen of the former and several of the latter are here reported from southern New Guinea, to which region they are doubtless non-breeding visitors. A russatus-like form from Timor requires further study. The ranges of C. rufomerus and C. crassirostris are possibly largely governed by the distribution of their putative host Gerygone dorsalis; old, poorly documented records of crassirostris from Sorong, Halmahera, Ternate, Ambon and Gorong, whence no species of Gerygone has been reported, are considered to require confirmation. Attention is drawn to the interesting relationship between C. minutillus and C. russatus as these species are here construed. In Borneo they appear to enjoy breeding sympatry without hybridizing (C. m. cleis, C. r. aheneus), whereas in Australia they appear to be hybridizing on secondary contact (C. m. minutillus, C. r. russatus). Such a situation has parallels elsewhere in zoology. Finally, it is suggested that the colour of the bare periophthalmic ring or eyerim of adult females is of taxonomic significance within the group; however, for females of several forms the colour of this character remains unrecorded.