https://www.academia.edu/Papers/UploadAbstractThe wetland of the Lakes Koronia and Volvi is of international importance, supporting high numbers of wintering migratory waterbirds. Although protected under the Ramsar Convention, pollution levels have increased enormously in the last two decades, damaging the natural environment. The aim of this thesis was to evaluate changes in the waterbird species populations recorded in the mid-winter counts since 1968 in the Ramsar Wetland of the Lakes Koronia and Volvi, in Northern Greece.
Data regarding waterbird populations were collected from the Hellenic Ornithological Society (HOS) and individual ornithologists who carried out the mid-winter counts. Data regarding environmental factors and pollution were collected from the Environmental Sector of the Ministry of Northern Greece and the Master Plan for the recovery of Lake Koronia. Data regarding fish populations were collected from the Fishing Directorate of the Prefecture of Thessaloniki. Data was presented in tables and graphs and analysis was performed to assess differences between waterbird populations and time. Individual species and groups of species of waterbirds were analyzed, as well as the total number of waterbirds. Fish populations vs. time and fish populations vs. fish-eating waterbirds were correlated. Variables characterizing pollution, climate and water use for irrigation vs. time, were analyzed. Data was not always sufficient for statistical analysis because of unavailability.
In 2002, Lake Koronia completely dried out with the result that large numbers of fish and waterbird deaths were documented. Wintering waterbirds populations also declined following this incident. After 2003, rainfall increased and the lake was regenerated. High numbers of waterbirds reappeared in the mid-winter counts of 2005. The fact that during the last few years Lake Koronia has again attracted a constant presence of pelicans, grebes and herons, is a good sign that the lake’s ecological status may be improving.
Lake Volvi has not been affected as much by pollution and drought. The area surrounding the lake is less densely inhabited, there are no industries and farmland irrigation occurs at a much lower level than Lake Koronia. However, fish species populations were gradually declining. Several duck species and coot are regularly counted in Lake Volvi, contributing significantly to the total waterbird counts. These species counts have dramatically declined in Lake Volvi since 1997. An occasional increase in wintering waterbirds observed in 2002 in Lake Volvi was due to fish-eating birds, mainly grebes. This is unlikely to be because of local factors, but more likely as a consequence of changes taking place elsewhere in Europe. The reasons leading to the above changes remain unclear, based on the present available data. Correlation of waterbird counts in Volvi and Koronia, with data from other Greek wetlands, would lead to useful conclusions and is one of several priorities for future analysis.
