Many populations of long‐distance migrants are declining and there is increasing evidence that declines may be caused by factors operating outside the breeding season. Among the four vulture species breeding in the western Palaearctic, the species showing the steepest population decline, the Egyptian Vulture Neophron percnopterus, is a long‐distance migrant wintering in Africa. However, the flyways and wintering areas of the species are only known for some populations, and without knowledge of where mortality occurs, effective conservation management is not possible. We tracked 19 juvenile Egyptian Vultures from the declining breeding population on the Balkan Peninsula between 2010 and 2014 to estimate survival and identify important migratory routes and wintering areas for this species. Mortality during the first autumn migration was high (monthly survival probability 0.75) but mortality during migration was exclusively associated with suboptimal navigation. All birds from western breeding areas and three birds from central and eastern breeding areas attempted to fly south over the Mediterranean Sea, but only one in 10 birds survived this route, probably due to stronger tailwind. All eight birds using the migratory route via Turkey and the Middle East successfully completed their first autumn migration. Of 14 individual and environmental variables examined to explain why juvenile birds did or did not successfully complete their first migration, the natal origin of the bird was the most influential. We speculate that in a declining population with fewer experienced adults, an increasing proportion of juvenile birds are forced to migrate without conspecific guidance, leading to high mortality as a consequence of following sub‐optimal migratory routes. Juvenile Egyptian Vultures wintered across a vast range of the Sahel and eastern Africa, and had large movement ranges with core use areas at intermediate elevations in savannah, cropland or desert. Two birds were shot in Africa, where several significant threats exist for vultures at continental scales. Given the broad distribution of the birds and threats, effective conservation in Africa will be challenging and will require long‐term investment. We recommend that in the short term, more efficient conservation could target narrow migration corridors in southern Turkey and the Middle East, and known congregation sites in African wintering areas.
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.
Assessing whether conservation management actions are effective requires a good understanding of the demographic parameters that contribute to the population growth rate. Among the key demographic parameters influencing a population, immigration is one of the most difficult to measure empirically but may mask or accentuate the effects of conservation measures. We use an integrated population model to assess whether a population increase of a large raptor species can be explained by high fecundity and survival resulting from local conservation measures, or whether immigration may have contributed to population growth. We monitored the Eastern Imperial Eagle (Aquila heliaca) population in Bulgaria from 1998 to 2014, and tracked juveniles using satellite transmitters to estimate survival probability over the first three years of life. We used intensive territory monitoring of breeding birds to estimate survival probabilities and fecundity of birds older than 3 years. The Imperial Eagle population in Bulgaria increased by about 11 % per year between 1998 and 2014 (k = 1.111, 95 % credible interval 1.076-1.156). While local conservation measures have succeeded in reducing nest loss and the mortality of adults (adult survival = 0.924; 0.887-0.955), high mortality of juveniles during their first year of life resulted in only 12 % of fledglings surviving to adult age. Based on these survival probabilities and the estimated fecundity of breeding pairs in Bulgaria (1.063; 0.932-1.203), some immigration may have contributed to the population growth in Bulgaria. Because the integrated population model accounts for all the uncertainty associated with disparate data sources, the estimated immigration rate was too Communicated by
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.
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