Estimates of dispersal propagule loads on woodpecker natural history collection specimens

Bird-mediated dispersal is presumed to be important in the dissemination of many different types of organisms, but concrete evidence remains scarce. This is especially true for biota producing microscopic propagules. Tree-dwelling birds, such as woodpeckers, would seem to represent ideal dispersal vectors for organisms growing on standing tree trunks such as epiphytic lichens and fungi. Here we utilize bird natural history collections as a novel source of data for studying dispersal ecology of plants, fungi, and micro-organisms. We screened freshly preserved specimens of three Finnish woodpecker species for microscopic propagules. Samples were taken from bird feet as well as chest and tail feathers. Propagules were extracted using a sonication-centrifugation protocol and the material obtained was studied using light microscopy. Diverse biological material was recovered from all specimens of all bird species, from all positions sampled. Most abundant categories of discovered biological material included bryophyte fragments, fungal spores and vegetative propagules of lichens. Also freshwater diatoms, bryophyte spores, algal cells, testate amoebae, rotifers, nematodes, pollen, and insect scales were identified. The method developed here is applicable to living specimens as well, making it a versatile tool for further research. Our findings highlight the potential of bird-mediated dispersal for diverse organisms and showcase the use of natural history collections in ecological research.