61 ACTA ZOOLOGICA BULGARICA Acta zool. bulg., Suppl. 3, 2011: 61-70 Introduction The Eastern Imperial Eagle inhabits a large area of the Palearctic region along the forest-steppe belt, although its distribution is highly scattered (DEL HOYO et al. 1995). World population consists of a few thousand breeding pairs only, and the species is classified as ‘Vulnerable’ by the IUCN Red List of Threatened Species (BIRDLIFE 2009). In spite of the high conservation priority of this species, only a fraction of the populations is monitored regularly (HORVÁTH et al. 2002), although the quality of avail- able data increased considerably during the last dec- ade, especially for the largest eastern populations (e.g. BELIK et al. 2002, KARYAKIN et al. 2008). Long- term monitoring of Eastern Imperial Eagle popula- tions, which would enable us to evaluate changes in the population size, distribution, breeding success or mortality (FERRER 2001), are extremely rare and probably only two significant populations have been monitored continuously over the decades. One of these populations in the Naurzum Reserve in North- Kazakhstan remained stable since 1978 (BRAGIN 1999, KATZNER et al. 2006), while the other popu- lation in the Carpathian Basin in Central Europe increased significantly since 1977 (DANKO, CHAVKO Population Dynamics of the Eastern Imperial Eagle (Aquila heliaca) in Hungary between 2001 and 2009 Márton Horváth 1 , Iván Demeter 1 , Imre Fatér 1 , Gábor Firmánszky 2 , András Kleszó 3 , András Kovács 1 , Tamás Szitta 3 , Imre Tóth 4 , Tamás Zalai 5 and János Bagyura 1 1 MME BirdLife Hungary, Budapest, Költő u. 21., H-1121, Hungary; E-mail: horvath.marton@mme.hu 2 Aggtelek National Park Directorate, Jósvafő, Tengerszem oldal 1., H-3758, Hungary 3 Bükk National Park Directorate, Eger, Sánc u. 6., H-3304, Hungary 4 Körös-Maros National Park Directorate, Szarvas, Anna-liget 1., H-5540, Hungary 5 Hortobágy National Park Directorate, Debrecen, Sumen u. 2, H-4024, Hungary Abstract: The Eastern Imperial Eagle (Aquila heliaca SAVIGNY 1809) reaches the western border of its range in the Carpathian Basin, which is the largest known population outside Russia and Kazakhstan. An increasing trend of this population in Hungary and also in the nearby areas of Slovakia has been reported since the 1980’s, when the number of breeding pairs supposedly reached the historical minimum. In this study we evaluated the dynamics of the Hungarian Imperial Eagle population between 2001 and 2009. As a result of the continuous increase of the population the monitoring program revealed 105 nesting pairs by 2009. While an expansion of the breeding area towards lowland agricultural habitats was observed, the ratio of pairs inhabiting the historical mountainous breeding habitats decreased from 50 % to only 15 % during the study period. The frequency of the two- and three-chick broods in respect to single-chick broods increased in comparison to the 1980-2000 period showing a higher average annual productivity of the population (1.15 fledglings per nesting pair). Besides the favourable changes in population trend and productivity, the area expansion in the recently occupied lowland habitats also raised several new threats to the population, such as the increased number of illegal poisoning incidents and more frequent collisions with vehicles. Key words: population dynamics, breeding success, agriculture, raptor, Hungary