A population viability analysis on the declining population of Little Owl (Athene noctua) in Denmark using the stochastic simulation program VORTEX

When a bird population is facing extinction, ecologically artificial conservation actions such as feeding and captive breeding may be considered as temporary efforts to rescue the population remains until environmental conditions for a self-sustaining population have been restored. Population viability analysis can be used to evaluate different management options for endangered bird populations. Here we use the program VORTEX to explore different management strategies using the Danish population of Little Owl (Athene noctua) as a model species. The Little Owl is declining in several countries, including Denmark, where lack of food during the breeding season has been identified as the main reason for the decline. Four scenarios were run, simulating 25 years of population dynamics: (1) "do nothing" scenario, (2) captive breeding scenario where individuals are supplemented to the population, (3) food supplementation or habitat improvement scenario and (4) scenario combining captive breeding and food supplementation/habitat improvements. In scenarios where no management actions were taken the population went extinct within 12 years. When supplementing individuals continuously the population remained extant but the population size remained small. Food supplementation/habitat improvements can restore the population, though there must be capacity to secure food/habitat for a minimum of 100 individuals to minimize genetic losses. By combining food supplementation and the release of captive bred individuals, the population has a chance of being restored and become independent of human aid. This study exemplifies how management scenarios can be used to guide managers to make informed decisions.