Conservation measures undertaken to improve the population status of eastern imperial eagle (Aquila heliaca) in Bulgaria

Abstract This study presents the results of conservation measures undertaken and their impact on the eastern imperial eagle population in Bulgaria. The species is distributed in the south-eastern part of the country, as there is only one known pair in central Bulgaria. During the period 2009-201 3, 28 different breeding territories were occupied. The population increased by 20%, as the number of pairs that occupied breeding territories increased from 20 in 2009 to 24 in 201 3. In general, the mean values of the breeding parameters of the eastern imperial eagle population for the period 2009-201 3 were as follows: productivity (P) 1 .03±0.1 8; breeding success (BS) 1 .1 8±0.21 ; and fledgling success (FS) 1 .68±0.1 6. The annual survival rate of breeders varied from 0.795 to 0.932. The most important factor causing the mortality of immature eagles was electrocution. Shooting and poisoning have become important mortality factors, too. Guarded pairs had a higher mean breeding success (1 .32±0.88) than non-guarded pairs (1 .06±0.91 ). As a whole, 39% of all artificial nests installed in the period 2009-201 3 were occupied by birds of different species. During the period 2008-201 3, a total of 23 juvenile eastern imperial eagles were tagged with satellite/GPS transmitters. In addition, 608 hazardous electric poles in the territories of seven pairs were insulated. Supplementary feed was provided for 1 4 pairs once a week during the autumn-winter seasons (October - March). A total of 483 supplementary feedings took place, 450 ofwhich also included monitoring in order to record the effectiveness of this activity. Abstrakt Štúdia prezentuje výsledky ochranárskych opatrení a ich vplyv na populáciu orla královského v Bulharsku. Druh sa vyskytuje v juhovýchodnej casti krajiny, v centrálnom Bulharsku je známy len jeden pár. V období 2009-201 3 bolo obsadených 28 rôznych hniezdnych teritórií. Populácia narástla o 20 %, pocet párov s hniezdnymi teritóriami sa zvýšil z 20 v roku 2009 na 24 v roku 201 3. Stredné hodnoty parametrov hniezdenia orlov královských boli v období 2009-201 3 nasledovné: produktivita (P) 1 ,03 ± 0,1 8; hniezdna úspešnost (BS) 1 ,1 8±0,21 , úspešnost vyletenia mládat (FS) 1 .68±0,1 6. Rocná miera prežitia hniezdiacich jedincov bola 0,795-0,932. Najdôležitejším faktorom, spôsobujúcim mortalitu mladých orlov boli usmrtenia po zásahu elektrickým prúdom spolocne s nelegálnymi odstrelmi a otravami. Strážené páry mali vyššiu hniezdnu úspešnost (1 ,32±0,88) ako nestrážené páry (1 ,06±0,91 ). Celkom bolo obsadených vtákmi rôznych druhov 39 % umelých hniezd inštalovaných v období 2009-201 3. V období 2008-201 3 bolo celkom 23 mladých orlov královských oznacených satelitnými vysielackami s GPS jednotkou. V teritóriách siedmich párov bolo izolovaných 608 nebezpecných stlpov elektrického vedenia. V jesennom a zimnom období (október až marec) sa raz za týžden realizovalo prikrmovanie 1 4 párov orlov. Celkom sa zrealizovalo 483 prikrmovaní, na 450 z nich bolo súcastou sledovanie efektivity tejto cinnosti.