The avian community of the Karen Mogensen Reserve, wealth of biodiversity within the poorly investigated and threatened environments of Northwestern Costa Rica

Northwestern Costa Rica is among the least known districts of the country in terms of ornithic fauna, despite being characterized by some of the most threatened forest ecosystems of Mesoamerica. Within this region, in the framework of an ongoing international cooperation program, we had the opportunity to investigate the Karen Mogensen Reserve, a protected area distinguished by the presence of a great variety of habitats. Surveys carried out over a 20-year period revealed an avian community composed of 204 species - a high species richness compared to similar areas of northwestern Costa Rica - of which 115 breeding in the zone and other 14 potentially breeding. We recorded four IUCN globally Vulnerable or Near-Threatened species, along with five species reported for the first time from the region, with range extensions of more than 100 km. Twenty-six species, mostly breeding in the area, are at their southernmost range borders, hence greatly susceptible to global environmental alterations, such as climate change. Besides, our study revealed the presence of two species endemic to a restricted area of Central America and four subspecies endemic to Costa Rica, along with breeding populations of two species that are geographically isolated from the main ones. Our analysis led to the ecological characterization of the resident avian community, showing that the 65% of the species is strictly associated to the understory or middle tree level, therefore more vulnerable to environmental change and susceptible of local extinction. These results stress the importance of the area for bird conservation within a vulnerable environmental context, and prompt the continuation of periodic bird surveys and the improvement of local conservations measures. The data collected will be an important tool for future studies aimed at evaluating the consequences of habitat fragmentation and to monitor the effects of climate change on the resident avifauna. We exhort the creation of programs that integrate bird monitoring, ecological research, conservation initiatives, and the involvement of the local communities, by promoting environmental education, capacity-building, and income generation. On this aim, the Karen Mogensen Reserve may represent a convincing model and valuable example to apply in similar contexts of the Neotropics. Eventually, the present study is a promising starting point for an exchange of ornithological knowledge between Italian and Costa Rican researchers.