Mortality Factors of Dalmatian Pelicans (Pelecanus crispus) Wintering in Macedonia, Greece

Abstract

A survey of dead Dalmatian Pelicans (Pelecanus crispus) at Kerkini Lake, Greece, the major wintering site in Europe of this world-endangered species, was undertaken to investigate the causes of high mortality that occurred during 1991–93. In February 1991, 30% of the population wintering on the Lake (30 individuals) were found dead, the majority (85%) having died of natural causes. A loss of this magnitude does not reflect only locally or on the genetic stock of the species but is also a matter of grave concern relative to its conservation world-wide.Most mortality of the Pelicans coincided with subzero temperatures and the Lake freezing over — conditions that direct fish to deep waters, and make them unavailable to the Pelicans. Necropsies were carried out on the carcasses of 13 Pelicans, including stomach and gizzard, etc., contents' analysis, and gross pathological, bacteriological, toxicological, and parasitological, examinations. All the carcasses found at Lake Kerkini were dehydrated and emaciated. No food was found in the digestive system of the Pelicans, but there was a heavy parasite burden. Species of seven helminth genera were detected in the carcasses, three of them (Bolbophorus, Contracaecum, and Synhimantus) being reported for the first time in Greece. Contracaecum spp. in large numbers (up to 875 worms per bird), were found in the digestive system of all the carcasses. Most parasites were observed to penetrate the wall of the gizzard, causing haemorrhages and ulcers. No evidence of chlorinated hydrocarbon contamination or bacterial infection was found. Mycotic lesions were detected in the air-sacs of one Dalmatian Pelican, which may have contributed to the death of that particular individual in connection with the parasite burden.