Type of Material, Not Tree Hole Characteristics Shapes Uropodina Mites’ Species Composition in Excavated Tree Holes

Abstract

Uropodina mites are organisms regularly found in the breeding sites of vertebrates. However, studies devoted to the nest dwellers of hole-nesting birds have been performed nearly exclusively in artificial places, i.e., nest boxes. Here, we describe an assemblage of mites from the Uropodina group living in excavated tree holes. We performed this study in western Poland, sampling material from 49 tree holes excavated by great spotted and black woodpeckers. We divided the material extracted from the tree holes into three categories: wood debris, remnants of bird nests, and remnants of insects. In total, we found 12 species from the Uropodina group. The two most numerous species, Leiodinychus orbicularis and Chiropturopoda nidiphila, constituted ca. 93% of the assemblage. Two other species, Apionoseius infirmus and Uroobovella obovata, were also relatively frequent. Among the assessed factors (woodpecker species, tree hole characteristics, and type of material), only the presence of insect remains, predominantly bat guano, affected species diversity and mite abundance the most. Our study is the first to describe an assemblage of Uropodina species in excavated tree holes and discover two extremely rare mite species, Ch. nidiphila and Nanteria banatica, related to the presence of bat guano in these cavities.