Because of the complex life cycle and the need for different habitats during the year, birds are very sensitive to external influences and changes in their habitats. It is therefore very important to monitor the situation and numbers in their population. It is of utmost importance to monitor the condition of their habitats, identify possible changes and threats to their habitats and to manage these areas sustainably. With systematic monitoring of bird populations, the Institute for Ornithology of the Croatian Academy of Sciences and Arts provides insight into qualitative and quantitative population status of birds of prey. Within the Lonjsko Polje Nature Park there are two ornithological reserves: Rakita and Krapje Đol. Birds of prey such as white-tailed eagle, the western marsh harrier and lesser spotted eagle are under high levels of threat. Within the park, the monitoring and ringing of birds of prey has been carried out, and the state of their populations has been systematically monitored. One of the biggest problems in this area is the succession because of abandonment of the traditional livestock breeding, which results in the reduction of pastures, which turn into thick vegetation and therefore have a negative impact on endangered populations of birds of prey.