The Remarkable Bird Monitoring Legacy at Prespa Unveiled

Long-term monitoring of living organisms provides valuable insights into large-scale ecological processes. These processes, which have been influenced by human actions, are often too slow to be observed in short-term projects. Birds have proven to be excellent indicators of such changes, whether they are sudden and obvious, like the loss of the virgin forest, or slow and discreet, like the gradual movement of tree lines to higher elevations. Monitoring wintering waterbirds in Prespa, particularly over the past three decades, has allowed the Macedonian Ecological Society to become more proficient in this task.

Wintering waterbirds in the Prespa region are highly responsive to climate change. In the last three years, during the mid-winter census in January, a decline in the number of waterbirds on the Macedonian side of Greater Prespa Lake has been observed. To provide a comparison, the total numbers of censused waterbirds for 2021, 2022, and 2023 were 11,063, 7,683, and 8,017, respectively. This decline is attributed to warmer winters and the global decline of the most common waterbird, the Coot. The contribution of changing water levels in Greater Lake Prespa to this decline is still uncertain.

The breeding colony of the Great Cormorant on Golem Grad Island in Prespa has experienced a noticeable decline in size between 2020 and 2022. Similar trends have been observed in the Grey Heron colony on the island. However, it turned out that the size of the Yellow-legged Gull colony was underestimated, with the actual number of active nests surpassing our expectations. An ongoing study on the diet of Great Cormorants during the breeding season reveals that their main prey is the endemic Prespa Bleak, although they occasionally consume large Carp specimens.

Bird populations in the meadows surrounding Greater Prespa Lake also face challenges, including succession with willows and rose hips. The population of Montagu’s Harrier appears to be strong with approximately 10 pairs, and ducks find suitable nesting cover in the lush tussocks. Smaller birds, such as Stonechats and Yellow Wagtails, serve as indicators of meadow conditions, with varying abundance in drier and wetter meadows, respectively.

The Rock Partridge, a species of interest for both hunters and conservationists, is studied due to its susceptibility to habitat changes and hunting. Although currently abundant in Galicica National Park, threats could impact its population in the future. Two individuals of this species were fitted with GPS transmitters to study their movement. One bird demonstrated the importance of transboundary efforts as it spent a significant amount of time in the Albanian part of the mountain. Unfortunately, the other bird was shot by an unknown poacher in the area. More birds will be fitted with transmitters to gather additional insights into their lifestyle.

The study and monitoring of birds have been conducted using sound scientific methodology, allowing future researchers to follow the same approach and draw valid conclusions. The data collected can be re-analysed with new analytical techniques and placed in an updated context. This provides valuable information for informing conservation measures, setting goals, establishing priorities, and setting quantitative targets. These efforts have also involved training future professionals and are being supported by the Prespa Ohrid Nature Trust -PONT, which recognises the importance of long-term funding for successful conservation outcomes.

Metodija Velevski and Danka Uzunova

Macedonian Ecological Society