Simple SummaryWe report on the occurrence of parasitic quill mites of the family Syringophilidae on the well-known avian group birds-of-paradise. Our investigation resulted in the discovery of two new species of mites belonging to the subfamily Picobiinae, which has never before been recorded on birds-of-paradise. We hypothesise that the interspecific sexual behaviour of paradisaeids, which involves copulation with non-closely related host species, may have facilitated the spread of syringophilid mites between different and unrelated host species. These findings highlight the potential role of sexual behaviour in the distribution and transmission of parasitic quill mites among avian hosts.AbstractWhile birds-of-paradise (Passeriformes: Paradisaeidae) are a well-known group of birds, our understanding of their parasites is still limited. This study reports on parasitic quill mites of the subfamily Picobiinae (Acariformes: Syringophilidae), which have never before been recorded on this group of birds. The mite specimens presented in this paper were collected from birds-of-paradise that had been captured in Papua New Guinea and Indonesia in the years 1910–1911 and are now deposited in the Bavarian State Collection of Zoology, Munich, Germany. Two syringophilid species are described as new to science: (i)Picobia frankeisp. n. from the magnificent riflebirdLophorina magnifica, the glossy-mantled manucodeManucodia ater, and the crinkle-collared manucodeManucodia chalybatus, and (ii)Gunabopicobia garylarsonisp. n. from the twelve-wired bird-of-paradiseSeleucidis melanoleucusand the lesser bird-of-paradiseParadisaea minor. We hypothesise that the presence of both picobiine species on phylogenetically unrelated paradisaeids may be caused by the sexual behaviour of these birds, where interspecific copulations may play a role in the switching of parasites between non-closely related host species.