High nesting success of the Imperial Eagles in Thrace

28 young Imperial eagles out of 23 pairs that had started incubation in the spring have successfully left their nests in 2017. The average nesting success this year for Bulgaria is 1.22 juveniles for a breeding pair. In European Turkey the nesting success is 1.36 juveniles, which is higher than the last’s year (0.98).  The number of the young Imperial eagles that have successfully left their nest is 38.

For the last 3 years the breeding success in Bulgaria is over 1.2 juveniles for a breeding pair, which is a very good indicator and gives hope for increasing the population of the species in the country. At the same time, however, there is no change in the number of the pairs of Imperial eagles in Bulgaria - 28 since 2015. The main reason for that is the high mortality rate in both young and old individuals – mostly because of electric shock in electric poles of the power distribution network, as well as by illegal shooting and poisoning. The loss of food and nesting habitats also has an adverse impact because it limits the possibilities for population growth and often leads to the loss of hunting grounds around the existing nests of Imperial eagles. This year, one of the well-known pairs in the Natura 2000 zone “Sakar” disappeared, but a new pair in SPA ”Derventski vazvishenia” was discovered.

In 2017, the maximum number of replacement breeding birds was recorded in the pairs - a total of 9 birds or 16.67%, the highest value of this indicator since 2000. The most likely cause is the death of one of the birds in the previously formed pairs. These results contrasted with the record low mortality rate for nesting eagles in 2016, barely 3.77% - the lowest for the past 10 years.

High nesting success of the Imperial Eagles in Thrace
© Márton Horváth