Feather position predicts colonisation by the quill mite Bubophilus asiobius in the flight feathers of the long-eared owl Asio otus

Host moult continually restructures the microhabitats available to feather-associated parasites, but the relative roles of temporal accessibility and mature-feather morphology in determining parasite distribution remain poorly understood. I investigated this problem in the quill mite Bubophilus asiobius inhabiting flight feathers of the Long-eared Owl Asio otus , separating feather colonisation from subsequent colony development. I examined 8424 feathers from 117 owls across 36 equally represented positions; 46 feathers were colonised and contained 7846 mites. Internal quill volume and wall thickness were additionally measured in 3600 feathers from 50 owls. Colonisation was strongly non-random among feather positions (within-host permutation test, P = 0.0002). Feather position predicted colonisation substantially better than quill morphology (AUC = 0.75 vs 0.59), while the full model reached AUC = 0.76; within-host permutation confirmed that position contributed information beyond morphology (P = 0.005). Among colonised feathers, mite abundance was positively associated with internal quill volume (Spearman's rho = 0.30, P = 0.045), whereas the association with wall thickness was not statistically significant (rho = 0.27, P = 0.066). These results support a two-stage model of microhabitat use in a permanent wildlife ectoparasite: colonisation is associated primarily with feather position, which may partly reflect transient access to developing quills during host moult, whereas internal quill volume may influence colony size after establishment. Thus, parasite distributions observed in mature plumage may retain a signature of short-lived colonisation opportunities created by host feather replacement.