Distribution of the parasitic mite Bubophilus aegolius sp. n. (Acariformes: Syringophilidae) on the Boreal Owl Aegolius funereus (L) (Strigiformes: Strigidae) and the low effectiveness of infestation

The mite family Syringophilidae (Acariformes: Prostigmata) includes permanent parasites of birds exclusively, occupying their quill feathers where they reproduce and feed on living tissue fluids, piercing the quill-wall with their long and stiletiform chelicerae. The Boreal Owl, Aegolius funereus (L.) (Strigiformes: Strigidae) is parasitised by the Bubophilus aegolius, which is a new species of syringophilid mite described herein. In our study a total of 55 Boreal Owls were examined, including birds from Poland, Austria, Switzerland, Germany, Czechia, Slovakia, Sweden, Finland, and Norway. A total of four host specimens from Poland, Switzerland, and Finland were infested by Bubophilus aegolius (index of prevalence IP = 7.3; 95% confidence interval for prevalence (Sterne’s method) CI = 2.5–17.9). In the material consisting of 14 juvenile (in the 1st calendar year) and 41 adults (in the 2nd calendar year or older) birds, only juvenile hosts were infested (IP = 28.6%; CI = 10.4–57.4). Among 3,190 examined feathers (primaries (N = 1,100), secondaries (N = 1,430), rectrices (N = 660), quill mites were found only in four feathers, each feather from a single host specimen: in two small secondaries, S12, S13, and in two middle rectrices R1. This low prevalence may be related to the solitary behaviour of owls and the marginal role of horizontal transfers of parasites between hosts. Hypothetically, the low number of infested feathers on the host indicates low effectiveness (= high mortality) during transmission, where – in each case – only one fertilised female foundress (dispersal stage) was able to transfer from the parent to the offspring and enter a new quill feather.