The Black-winged Monarch (Monarcha frater): Geographic variation, taxonomy, a "new" population, and an enduring mystery in migration

The Black-winged Monarch (Monarcha frater) inhabits low-mid elevation forests across New Guinea and far north-eastern Australia. Of its four recognized subspecies, M. f. canescens is migratory, breeding in tropical north-eastern Australia from approximately November–March. The non-breeding range of M. f. canescens, apart from some individuals overwintering in Australia, has been unknown for > 100 years. Data from 194 New Guinean and Australian specimens and a literature review have not solved this mystery; the narrow latitudinal range of the intratropical migration may inhibit use of GPS loggers in resolving the migration route. Field work in central and western parts of southern New Guinea is needed. Specimen data, however, revealed an essentially overlooked population in north-western New Guinea east of the Bird's Head Peninsula phenotypically indistinguishable from nominate M. f. frater of that Peninsula. Future genomic analysis of the complex will be largely done from toepad skin because frozen tissue samples for DNA analysis exist only of four individuals of what we suggest should be elevated to species rank as M. periophthalmicus. We discuss how genomic analysis might distinguish among alternative taxonomic hypotheses of one, two or three species. We suggest English names for what we consider to be three diagnosable taxa worth recognizing at species rank in this group: Arfak Monarch corresponding to M. frater (Bird's Head Peninsula and the "new" population of north-western New Guinea); Pearly Monarch for M. canescens (Australia and still unknown non-breeding range), and Masked Monarch for M. periophthalmicus (including kunupi, elsewhere in New Guinea).