Survival rate and mortality of juvenile and immature eastern imperial eagles (Aquila heliaca) from Bulgaria studied by satellite telemetry

A long-living species like A. heliaca has a natal dispersal period lasting several years. This period is crucial for the survival and conservation of the eagles. In this study we present mortality factors and the survival rate of juvenile and immature A. heliaca from Bulgaria as established by satellite telemetry. A total of 20 juvenile A. heliaca were fitted with GPS / Argos transmitters in their nests in Bulgaria. Fourteen birds were tracked till their death and the bodies were found. Tracking allows the survival rate of juvenile and immature A. heliaca to be estimated for the first time. It is 59.1% for the first calendar year, 83.3% for the second calendar year and 80.0% for the third calendar year. The main mortality factor for juvenile and immature A. heliaca from the Bulgarian population is electrocution, which caused 59.0% of the mortality cases. Other threats identified are shooting, poisoning and collisions. Most of the fatalities of these tracked eagles occurred in Bulgaria (50%) and Turkey (43%). Thus, Turkey is a key country for conservation of the Bulgarian population ofA. heliaca during its dispersal period. Eagles from Bulgaria have been recorded dispersing further south, to Sudan and Saudi Arabia. Conservation efforts are needed both inside and outside Bulgaria in order to reduce mortality. International collaboration and the exchange of experiences should be part of any conservation strategy or plans focused on the eastern imperial eagle. Abstrakt: U dlhožijuceho druhu A. heliaca trva disperzia z miesta vyliahnutia niekoľko rokov. Je to obdobie veľmi doležite pre prežitie a ochranu orlov. V tejto studii prezentujeme faktory mortality a preživanie mladých a imaturných A. heliaca z Bulharska na zaklade studia satelitnou telemetriou. Celkom bolo v hniezdach v Bulharsku vysielackami GPS / Argos oznacených 20 mladých A. heliaca. Strnasť vtakov bolo sledovaných až do smrti vratane nalezov kadaverov. Ide o prve taketo studium preživania mladých a imaturných jedincov A. heliaca. Preživanie ma hodnotu 59.1 % v prvom kalendarnom roku, 83.3 % v druhom a 80,0 % v treťom kalendarnom roku. Hlavným faktorom mortality sledovaných jedincov z bulharskej populacie je smrť v dosledku zasahu elektrickým prudom, ktorý sposobil 59,0 % pripadov mortality. Ďalsie identifikovane hrozby su zastrely, otravy a kolizie. Vacsina pripadov mortality sledovaných orlov nastala v Bulharsku (50%) a v Turecku (43%). Preto je Turecko kľucovou krajinou pre ochranu bulharskej populacie A. heliaca pocas jeho disperzie. Orly z Bulharska sa rozptyľuju aj ďalej na juh, do Sudanu a do Saudskej Arabie. Preto je potrebne ochranarske usilie s cieľom zniženia mortality tak vo vnutri ako aj mimo Bulharska. Medzinarodna spolupraca a výmena skusenosti by preto mala byť sucasťou každej strategie ochrany a planov zameraných na ochranu orla kraľovskeho.