POPULATION DECLINE OF THE LITTLE OWL(ATHENE NOCTUA SCOP.) IN THE CZECH REPUBLIC

摘要

A change of land use is oftencited as a causal factor in the decline of many spe-cies of farmland birds. Populations of the LittleOwl (Athene noctua Scop., 1769) have notablydecreased throughout Europe in the last 60 years,including the Czech Republic. The aims of thisstudy were to estimate the recent population trendof the Little Owl and to analyze the importance ofaltitude and grassland habitat within Little Owlterritories. The population trend of the Little Owlin the Czech Republic has still decreasing ten-dency. The population density dropped from 0.33breeding pairs (bps) 10 km~(-2)to 0.12 bps 10 km~(-2)in the first (1993-1995) and second (1998-1999)monitoring program, respectively. The decline isapparent also from results from last Little Owlmonitoring program which were carried out in2005-2006 on 35 study plots (4607 km2). Theaverage population density was estimated at 0.1bps 10 km~(-2). A distinct feature of these recentpopulations is that they occur in the places withrelatively high local density (core areas) in com-parison to the surroundings, which are unoccu-pied. At present, the Little Owl rarely breeds innatural tree cavities, but rather the majority ofnesting sites are situated in human artifacts, espe-cially within agricultural objects. Areas in whichthe Little Owl occurs have a significantly largerproportion of grasslands and are situated at loweraltitudes. We suggest that the changes in agricul-tural landscape associated with disappearanceof traditional farming management of grassland habitats, forceful pasturage and regular mowingwere the main factors in this long-term popula-tion decline. The recent decrease of Little Owlscould be also the consequence of the existence ofsmall isolated populations in which mortality isnot balanced by immigration from surroundingareas.