Revision of Harry Potter and the fate of the European barn owl from Fri, 2018-06-15 16:31

The barn owl (Tyto alba) population in Belgium consisted of only a few brooding pairs 40 years ago. The “Kerkuilwerkgroep”, a group of highly engaged citizens, conducted a tremendous effort to protect the barn owl population by placing nest boxes around Flanders. These nest boxes are yearly monitored and checked for brooding success. As a result, the population of barn owls in Flanders has grown substantially, containing an estimated 2250 birds today. In addition, the group has collected specimens and extensive morphological and physiological data on barn owls from road casualties over the past 10 years. From these data, a shift in coloration of the owls has been noticed: while owls used to be exclusively dark, birds encountered today are more and more white coloured with ca 10% of the birds being even completely white. Plumage coloration and spottiness are genetically determined (Roulin and Dijkstra, 2003) and can result from local adaptation to habitat choice (wood vs areal habitat) (Dreiss et al., 2012). However, the change in color may also result from breeding with non-european birds: amongst the road casualties, more and more barn owls are encountered from captivity which may be linked to the Harry Potter hype. The barn owls of Harry Potter and his friends play a prominent role in the movies, which have led to a huge commercial breeding trade of barn owls from around the globe. Unfortunately, many bred owls are released when owners realise that they are not the most easy pet to keep. The number of released birds in Flanders since 2000 ranges from 850 – 1700 birds. Although only a fraction of these birds survive in the wild, their impact on the genetic diversity of the resident population may be substantial. These birds from captivity are very often imported from other continents and represent different subspecies of Tyto alba. Within Europe, genetic diversity of Tyto alba decreases from southwestern to northeastern Europe, consistent with a postglacial range expansion (Antoniazza et al., 2010) from a single refugium located on the Iberian peninsula (Antoniazza et al., 2014). Our own recent work using mitochondrial DNA and including COI sequences from Genbank from owls around the world show highly supported clades that grouped specimens per continent. This suggests that strong genetic breaks are present between owls originating from different continents. In the current project, we aim to characterise the genetic diversity of the current Tyto alba population in Belgium and compare this to the genetic diversity from before the Harry Potter hype. This comparison will highlight whether/how much genetic material from foreign subspecies has entered our local population. In the best case scenario, Harry Potter has contributed to the growth of Tyto alba in Europe with no detrimental effects for the species; in the worst case scenario, the import of “exotic” barn owls into Europe has substantially altered the genetic composition of Tyto alba which would provide a scientific basis for a stronger regulation on the import and release of barn owls. Such a regulation is non-existent at this moment. In addition, the suggested approach may yield a SNP panel for the quick identification of exotic specimens, which may facilitate decisions on whether birds in sanctuaries can be released in the wild or have to be euthanised. This project merges the tremendous knowledge on barn owls obtained from good citizen science with state-of-the-art technologies applied at RBINS which may lead to an important contribution to conservation research.