TDK conference 2017

The eastern imperial eagle (Aquila heliaca) is a globally endangered, large-sized, territorial species of bird of prey. The majority of its European population breeds in the Carpathian Basin. The size of the Hungarian population is constantly increasing due to the species conversation project started in 1974. In order to evaluate the success of the project we estimated the survival probabilities of the Hungarian breeding pairs for 2011–2016. Naturally shed feathers collected at the nest sites and feathers pulled from chicks were used for the analysis. The birds were individually identified through molecular sexing and genotyping based on microsatellite loci using DNA extracted from feathers. Capture histories for 338 breeding individuals were constructed from presence data based on these DNA profiles. These data were analysed with capture-recapture method to estimate survival probabilities using the Cormack-Jolly-Seber model suitable for open populations. A version of our model with fixed recapture probabilities (estimated from yearly sampling effort) was used in order to get reliable survival estimates for the last time interval as well. In those cases, when we could not sample a breeding bird in a particular year, we used the samples of the chicks from the same year to identify the missing bird, thus gaining additional estimated presence data.

According to the AIC-based model selection, the best model was the one with fixed recapture probabilities and survival varying among years and between sexes. Female survival was higher, 0.89 (CI: 0.86-0.92) on average, while male survival was 0.81 (CI: 0.72-0.88) on average. For both sexes, survival between 2011 and 2012 was lower than the average. The additional estimated presence data reduced the uncertainty of the estimates of survival, especially for males.

Higher female survival can be explained by the different behaviour of the two sexes: the males face more danger as they spend more time hunting and protecting the territory. The lower survival for 2011–2012 may be in connection with the high poisoning rates at that time.