Current expansion of the Barn Owl (<i>Tyto alba</i>) (Tytonidae, Aves) in Northern Eurasia

Abstract

   In the north of Eurasia, until the mid-twentieth century, the Barn Owl (Tyto alba) was sporadically distributed only in the Baltic states, in the west of Belarus and Ukraine, and in Moldova. Once, in 1942, a vagrant bird was caught in Turkmenistan also. At the end of the 20th century, reports appeared of rare recordings of barn owls in Eastern Europe, and since the beginning of the 21st century, pronounced expansion of these birds has been noted, observed in the south of Ukraine, Crimea, Ciscaucasia, and Transcaucasia. Different subspecies living in Central and Southern Europe and the Middle East are simultaneously expanding their nesting areas, namely: a. guttata, T. a. alba, and T. a. erlangeri. However, visual identification of subspecies and clarification of the direction of their expansion are complicated by the similarity of various forms and their significant individual variability associated with age, sex, intergradation with neighboring subspecies and other factors. The appearance of sedentary barn owls in new places is usually preceded by their post-nesting dispersion, directed in all directions and in some cases reaching 1–2 thousand km from the place of birth. Owing to the expansion of its range, barn owl populations have increased many times in a number of regions over the past decades, but accurate estimates of their numbers there are missing due to the rarity and sporadical nature of new finds, the very secretive lifestyle of these birds and insufficient knowledge of their ecology and ethology in the north of Eurasia. The article examines the taxonomy of various barn owl populations in Northern Eurasia and main diagnostic characteristics of some subspecies living in the north of Eurasia, as well as analyzes features of their historical and current distribution and expansion in Eurasia. The author also discusses possible causes and mechanisms of the barn owl dispersion and touches on information on the dynamics of their numbers in few regions.