373 ACTA ZOOLOGICA BULGARICA Acta zool. bulg., 66 (3), 2014: 373-384 Terrestrial Ecology and Behaviour Research Article Introduction The Gyps vultures represent a scavenger guild composed of 8 species distributed in the Old World and specialised in feeding exclusively on carcasses of medium and large-sized mammals (Johnson et al. 2006). Of them, only the Griffon Vulture (Gyps fulvus Hablizl, 1783) is breeding in Europe (but also in Asia and until recently in North Africa). Its distribution in Europe, which in the past stretched north up to Germany and Poland, is currently restricted to the Mediterranean, with a population of more than 25 000 pairs (>95% of which in Spain), where it breeds in the Iberian Peninsula, the south of France, the Alps, the Apeninnes, the Balkans, Crimea and Caucasus (Cramp, simmons 1980, Ferguson-Lees, Christie 2001). In the Balkans, the Griffon Vulture was widely distributed and breeding in all countries across the peninsula in the 19th century (Cramp, simmons 1980). In Bulgaria, until the frst quarter of the 20th century, the species had a wide distribution throughout the country, being reported as numerous in many areas (reiser 1894). It was recorded as breeding in most large mountain ranges, namely Stara Planina (throughout), Rila, Pirin, Vitosha, and the Rhodopes, as well as the Provadiya-Royak plateau, but also in the lowlands and on cliffs at the Black Sea coast (e.g. Cape Kaliakra) and along the Danube River (DemerDzhiev et al. 2007, stoyanov 2010). At that time probably more than 1000 pairs bred in Bulgaria. Long-term Population Status, Breeding Parameters and Limiting Factors of the Griffon Vulture (Gyps fulvus Hablizl, 1783) Population in the Eastern Rhodopes, Bulgaria Dimitar Demerdzhiev 1 , Hristo Hristov 2 , Dobromir Dobrev 1 , Ivaylo Angelov 3 and Marin Kurtev 3 1 5 Leonardo da Vinchi Str., 4000 Plovdiv, Bulgaria; E-mail: dimitar.demerdzhiev@bspb.org 2 6480 Madzharovo, Bulgaria; E-mail: grifonvul@abv.bg 3 Gorno Pole 6480, Bulgaria; E-mail: ivaylo.d.angelov@gmail.com Abstract: The Griffon Vulture in Bulgaria declined during the frst half of the 20th century, from widespread and abundant to localised and very rare. In the 1970s the species was on the brink of extinction, represented by probably few scattered pairs in northeastern Bulgaria and less than 10 pairs in the south of Bulgaria, where one population, common to Bulgaria and Greece, survived in the Eastern Rhodope Mountains. Here we report the results of a 25-year long survey (1987-2011), which documents the steady increase in the population from 10 pairs distributed in 2 colonies, to 56 pairs in 7 colonies. During the study period, 450 juveniles fedged from totally 646 occupied nests, with mean breeding success of 0.77±0.14 and mean pro- ductivity of 0.71±0.16, indicating average values for Europe. The main limiting factor is the mortality after consumption of illegally set poisoned baits, targeted against carnivores, followed by shooting, collision and exhaustion. The human-wildlife confict in large areas and the increasing illegal use of poison baits in Greece are extremely hard to handle with. As a main conservation action for managing the Griffon Vultures we recommend the implementation of large-scale diverse public awareness campaign targeted at schools, kindergartens, governmental institutions, stock breeders, hunters and local communities. Key words: Population status, breeding, limiting factors, Griffon Vulture, Bulgaria