widespread

Demerdzhiev D., G. Gradev, S. Stoychev, I. Ivanov, T. Petrov and S. Marinrence of the species in 19 localities in the country forthe period 1970-1978. Between 1980 and 1993 thespecies was reported in 35 localities; however, therewere only nine cases of conrmed breeding (Pe t r o vet al. 1996). For or that period perio the population poplation was es estimated at 15-20 breeding pairs. With the intensiedornithological researh researh research after 1990 an an an an an an an the onsist onsist onsist onsist onsist onsist onsist onsist consist onsist onsistent stying studying stying of the Eastern Imperial Eagle istrib distribu istrib istrib istrib istrib istrib istrib istrib istrib istrib istrib istribtion, threats, and numbers during the period 1994-2002 (St o y c h e v 1997, Pe t r o v 1999), the numberof known pairs reached 13. For the same period thepopulation was estimated at 20-25 pairs (St o y c h e vet al. 2004) and 30-40 pairs (Na n k i n o v et al. 2004).If a population of large and long-lived raptors isto grow, it must have high survival rates of adult andsubadult individuals, iniials, iniials, presence presene presene presene presene of floaters, good goo goo goo goo goo goo goo goo breed bree bree bree bree bree bree bree breeing success, availability aailability aailability of suitable sitable sitable habitats ompris compris omprising breeding an an an foraging sites, age of rst rst rst rst rst rst rst rst rst rst rst rst rst repro reproduc repro repro repro repro repro repro repro repro repro repro repro repro reprotion and maturity, and mitigation of major limitingfactors (Ne w t o n 1979, Kat z n e r et al. 2006).The systematic research implemented over thepast decade revealed an obvious increase in the EasternImperial Eagle population in Bulgaria. Newly o o o occu opie territories were recorde reore reore reore reore reore reore in hilly an an an an an an an an an an an an an lowlan lowlan lowlan lowlan lowlan lowlan lowlan lowlan lowlan lowlan lowlan lowlan lowlan lowlan lowlan ar ar ar ar ar ar ar ar ar ar ar ar ar ar ar ar areas of the Sakar and the Western Strandja Mountainsas well as the Tundja Tnja Tnja rier river rier alley, valley, alley, while loss of ter ter territories was recorded in the mountain areas (Hr i s t o v,St o y n o v 2002, Demerdzhiev 2004, Demerdzhievm a n u s c r i p t, An g e l o v 2009). The species’ populationis estimated at 25-30 pairs, as 20 breeding territoriesoccupied by pairs were known in 2009.Material and MethodsField surveysSince 2000, the researh research researh an and an onseration conservation onseration atii activi atiities implemented by the Bulgarian Society for theProtection of Birds and Green Balkans NGO haveimproved the status of the Eastern Imperial Eaglein Bulgaria. The intensity of the monitoring and thequality of the gathere gathere gathere gathere gathere gathere gathered ata ata ata ata ata ata data were improe, improe, improe, improe, improe, improved, improe, improe, improe, ths ths ths ths ths thus ths ths ths ien ien ien ien ien iden ien ien ientifying the dynamics of the species’ population. Thesystematic regional studies carried out by the expertsof these two organizations every year minimized therisk of leaving territories occupied by eagles undetected. This method makes it possible to record theactual situation of the population (Ne w t o n 1979).One hundred and twenty-e 10x10 km UTMgrid squares in the areas harboring breeding EasternImperial Eagles were inspected every year or onceevery two years searching searhing searhing searhing searhing searhing searhing for newly opie occupied opie opie opie opie opie opie opie opie opie ter ter ter ter ter ter ter ter ter ter territories. In addition, 150 UTM grid squares, wherethe species was recorded during the breeding season with varying degrees of reliability of breeding,or which represent suitable habitats, were visited atleast once during the perio 20002009. 20002009. 02009. -2009. The inspe inspe inspe inspe inspe inspe inspec inspe inspetions involved transect methods used mainly alongriver valleys or streams, or examination of high and/or single trees in open habitats. Another method usedduring the inspections was observations from viewpoint (Bi b b y et al. 1999, Аn d e r s e n 2007). The st st stud sties were carried out mainly in the period February-May, when trees were not in full leaf and the nestscould easily be seen. Observations were also carriedout in June and July, monitoring the eagles’ behaviorin order to locate their nests. The degree of certaintyof breeding is according to Ha g e m e j e r, Bl a i r 1997.During the breeing breeing breeing breeding breeing perio perio perio perio perio perio perio (ebraryAgst (ebraryAgst (ebraryAgst (ebraryAgst (ebraryAgst (ebraryAgst (ebraryAgst (ebraryAgst February-August mon mon mon mon mon mon mon mon mon mon monitoring of occupied nests was carried out twice orthree times a month. During the autumn and winterperiod the breeding territory of each pair was visitedat least once a month. Risky nests sitate sitate sitate sitate sitate situate sitate near ar ar ar ar ar ar ar ar ar ar arable lans lands lans or roas roas roas roas roads roas roas were gare gare gare gare gare gare gare guarde gare gare gare ring ring ring ring ring during ring ring ring ring ring ring ring the bree bree bree bree bree bree bree bree bree bree bree bree breed bree bree bree breeing season by volunteers of the two organizations toincrease the breeding success. In cases when a pairbred in an unsuitable place, where the chances ofraising chicks were poor, the access to the nest washindered so that birds could not alight on the nest.Data analysesOccupied territories, breeding pairs, and populationbreeding parameters were recorded on an annual basis. The recorded data included adult survival ratean age strtre structure strtre strtre strtre of the breeing breeing breeing breeding breeing breeing breeing breeing breeing breeing breeing poplation. poplation. poplation. poplation. poplation. poplation. poplation. poplation. population. poplation. poplation. poplation. poplation. The es es es es es es es es es es es es estimates of the annual mortality of breeders (adult andsubadult) were based on the replacement of birds inpairs. The new partner is considered to replace adead mate. Howeer, Howeer, However, this assessment is not an abso abso abso abso abso abso abso abso abso abso abso abso abso abso absolute ale value ale e e e due e to the fact fat fat fat fat fat fat fat fat fat fat that sometimes it is impos impos impos impos impos impos impos impos impos impos impos impos impos impos impossible to record the replacement of a partner from thepair by an individual of the same age (Fe r r e r 2001).Breeding Eastern Imperial Eagles fon fon fon foun fon fon fon dead ea ea ea ea ea ea ea ea dur r r r r r r r ring the study period were also reporte. The ienti ienti identiation of plumage is according to Fo r s m a n (2005).Considering the different opinions regarding the42