# Distribution of the Quill Mite Bubophilus asiobius Parasitizing Western Palaearctic Owls of the Genus Asio

## TL;DR

This study explores the distribution of the quill mite Bubophilus asiobius in Western Palaearctic owls, revealing its presence in various feather types and suggesting recent ecological interactions.

## Contribution

The study documents the mite's infestation in a broader range of feather types and suggests a recent, unstable host-parasite relationship.

## Key findings

- Bubophilus asiobius was found in multiple feather types of Long-eared and Short-eared Owls but not in Marsh Owls.
- Feather growth appears to be a key factor in mite colonization, with quill size and wall thickness influencing mite numbers but not suitability.
- The mite's presence in various feathers suggests a recent and ecologically unstable relationship with its host owls.

## Abstract

Birds and their parasites have coevolved over millions of years, forming intricate relationships that shape biodiversity. Until recently, little was known about the mites parasitizing owl feathers. Quill mites of the family Syringophilidae (Acariformes: Prostigmata) are highly specialised ectoparasites that reside within feather quills. Despite their widespread occurrence, their diversity, distribution and host associations remain poorly understood. This study investigated the distribution and ecological interactions of the quill mite Bubophilus asiobius in the feather quills of Western Palaearctic owls of the genus Asio: the Long-eared Owl (Asio otus), Marsh Owl (Asio capensis) and Short-eared Owl (Asio flammeus).

A total of 196 owl specimens were examined. Feathers were categorised as follows: primaries (P), secondaries (S), rectrices (T), primary greater upper-wing coverts (PGUppC), secondary greater upper-wing coverts (SGUppC), alula feathers (Af) and scapular greater coverts.

Prevalence was relatively low across hosts: 9.3% (CI = 4.9%–16.5%; N = 108) in Long-eared Owl, 9.3% (CI = 4.5%–18.5%; N = 75) in Short-eared Owl and 0% in Marsh Owl (N = 13). In total, 27,440 flight feathers and coverts were inspected. Bubophilus asiobius was detected in primaries, secondaries, rectrices, PGUppC, SGUppC, Af and scapular greater coverts of Long-eared and Short-eared Owls. No mites were found in Marsh Owls.

Our findings indicate that Bubophilus asiobius exploits a broader spectrum of feather types in its hosts. We documented infestations in primaries, small inner secondaries, rectrices, Af, as well as in the primary and secondary greater coverts and scapular greater coverts of both the Long-eared Owl and the Short-eared Owl. The frequent occurrence of mites in primaries, secondaries and rectrices suggests that these feather types provide particularly favourable conditions for colonisation. The primary factor determining mite spread appears to be the availability of newly growing feathers. During feather growth, female mites colonise available quills and penetrate the walls irrespective of their thickness, enabling unrestricted foraging. Thus, quill size and wall thickness influence the number of mites that can establish within a feather but do not limit feather suitability for infestation. An alternative explanation is that the association between Bubophilus asiobius and owls of the genus Asio represents a relatively recent and ecologically unstable host–parasite relationship.