|Title:||Ecological aspects of Pygmy Cormorants Phalacrocorax pygmeus at Prespa, Greece, May-August 1996|
|Author(s):||Frank J. Willems & Etienne de Vries|
During the 1996 breeding season ecological research was carried out to investigate feeding ecological aspects and colony size of the Pygmy Cormorant Phalacrocorax pygmeus, a vulnerable bird species, at Prespa National Park, northwestern Greece.
As the breeding colony was inaccessible, colony size was estimated by counting colonial activity during one whole day in May, June and July, resulting in an estimate of 515-675 breeding pairs. These numbers are higher than any previous estimate. A possible explanation for this rise might be increased fish densities.
The numbers of foraging waterbirds were counted 9 times in a total of 33 plots during the period of May till July. Combining these counts with measurements of disturbance rate and several biotic parameters, it was found that densities of Pygmy Cormorants at feeding sites are negatively correlated with human disturbance and water depth.
A diet study was carried out by analysing pellets collected from a resting tree near the colony. Pellet contens were analysed using empirically derived regression equations from a reference collection of fish caught at Lakes Mikri and Megali Prespa. Nine different fish species were determined, yet 89 % of the fish mass consisted of Carp Cyprinus carpio (58%) and Ohrid Roach Rutilus ohridanus prespensis (31%).
The report contains: