Reasons for the breeding failures of the Egyptian vulture in Bulgaria and Greece

31.07.2016

The present study aimed to investigate the reasons for breeding failures in the steeply declining population of Egyptian vulture in Bulgaria and Greece (holding ca. 50% of the Balkan population of the species), so that its results may be further used to inform a more effective and adequate conservation of the species. The study was conducted in the period 2006-2015 for Bulgaria and 2011-2015 for Greece based on the observations compiled through the implementation of the monitoring activities of Egyptian vulture breeding territories in both countries, the nest guarding programme and the use of camera devices (trail cameras) installed in selected nests.

The average percentage of unsuccessful pairs per year in Bulgaria and Greece was 38% (n = 366 breeding attempts), with 37% per year for Bulgaria (for a period of 10 years) and 48% for Greece (for a period of 5 years). In total, 54% of unsuccessful pairs (n = 132) did not initiate breeding attempt at all, while 46% initiated a breeding attempt but failed in different stages of the breeding period. In 54% (n = 61) reasons for breeding failure remained unknown, for 26 % the reason for breeding failure was evidenced, and for 20% the reason was suspected based on expert’s opinion. For both evidenced (n = 16) and suspected (n = 12) causes for breeding failure, natural causes were much more frequent than human-induced causes. In the case of known causes of breeding failure (n = 16), natural drivers were represented by lack of experience in pairs (25%), predation (25%), diseases (12.5%) and weather conditions (6%), while in the case of human-induced causes they were represented by persecution (19%; registered only in Bulgaria and aiming at nest robbing and taxidermy) and poisoning (12.5%). In terms of the period, ca. 60% of the failures occur during incubation stage.

In Bulgaria (2006-2015), the lack of experience in pairs was the most frequent natural cause (40%, n = 10), followed by diseases (20%) and bad weather conditions (10%), while persecution (30%) was the most frequent human-induced cause for breeding failure. In Greece (2011-2015), most of the evidence collected (67%; n = 6) was related to natural causes for breeding failure (predation of chicks), while only 33% referred to human-induced causes (mainly poisoning of adults).

Considering the high proportion of cases with unknown causes of breeding failures, further research with more robust methodology is needed. Appropriate measures to reduce the rate of breeding failures are suggested, such as securing the nests and supplementary feeding programmes.

The full report is available here.

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